Ontogenetic allometry in the fang in the front-fanged Causus rhombeatus (Viperidae) displaces the fang along the upper jaw. Scale bars, 1 mm. We note the change in relative size of the upper jaw subregions: i, anterior; ii, fang; iii, posterior. d.a.o., days after oviposition.
I keep saying this to everyone: if you want to understand the origin of novel morphological features in multicellular organisms, you have to look at their development. "Everything is the way it is because of how it got that way," as D'Arcy Thompson said, so comprehending the ontogeny of form is absolutely critical to understanding what processes were sculpted by evolution. Now here's a lovely piece of work that uses snake embryology to come to some interesting conclusions about how venomous fangs evolved.
Basal snakes, animals like boas, lack venom and specialized fangs altogether; they have relatively simple rows of small sharp teeth. Elapid snakes, like cobras and mambas and coral snakes, are at the other extreme, with prominent fangs at the front of their jaws that act like injection needles to deliver poisons. Then there are the Viperidae, rattlesnakes and pit vipers and copperheads, that also have front fangs, but phylogenetically belong to a distinct lineage from the elapids. And finally there are other snakes like the grass snake that have enlarged fangs at the back of their jaws. It's a bit confusing: did all of these lineages independently evolve fangs and venom glands, or are there common underpinnings to all of these arrangements?
Let's start by looking at the phylogenetic tree and different fang arrangements. As you can see, those snakes with fangs at the back of their jaws (Natrix natrix, second from top) are interposed between one group of snakes with front fangs (the elapids, top), and another group with fangs in front (the vipers, third from top). We can imagine all kinds of scenarios that would produce that condition — front fangs are primitive, and Natrix secondarily lost them, or the fangs of all three are of independent origin and this is an example of convergence — but to resolve the question we need to look at some evidence. We need to examine embryos.
(Click for larger image)
a, Phylogeny. b, c, Adult skulls: lateral views (b); palate, schematic ventral views (c; maxilla coloured, fangs circled). Asterisks indicate species studied by electron microscopy. The evolutionary changes leading from an unmodified maxillary dentition to the different fang types in advanced snakes are indicated at the nodes: (1) continuous maxillary dental lamina, no specialized subregions—ancestral condition for advanced snakes; (2) evolution of posterior maxillary dental lamina—developmental uncoupling of posterior from anterior teeth; (3) starting differentiation of the posterior teeth with the venom gland; (4) loss of anterior dental lamina and development of front fangs.
This is where we begin to see some underlying unity. Vonk and others used sonic hedgehog staining to visualize the dental primordia in snake embryos (O Sonic Hedgehog, is there no process in which you are not involved, nothing in which your expression is not enlightening?) and mapped out the pattern of tooth generation. They identify an odontogenic band, a thin strip of tissue that gives rise to teeth, and note an interesting peculiarity: there are subdivisions into independent anterior and posterior dental lamina, and ablating the anterior lamina does not perturb the development of the posterior lamina. In essence, the snakes simply have a couple of separate tooth-generating zones in their embryonic jaws.
The cool observation is that even in front-fanged snakes, it is the posterior zone that generates the fangs. It is also this same primordium that buds off a tube and a sac that will make the post-orbital venom gland — even in the front-fanged snakes, they have a gland located way back behind the eye to produce venom.
These observations are diagramed below. The unspecialized dental lamina, the part that sprouts the generic small pointy teeth, is in green; the specialized posterior dental lamina, which makes fangs and the venom gland, is in orange. In all the venomous snakes, the venom gland is a tube that first extends forward, and then curls back to make the bulk of the gland even more posteriorly. The important point is that all of these snakes use the same small posterior scrap of embryonic odontogenic tissue to make fangs and glands — we can make a pretty solid argument that these structures are all homologous.
(Click for larger image)
Derived from serial sections. Left-hand side of the upper jaw is depicted, and only epithelial components are shown. Purple, shh expression; grey, tooth buds; green, unspecialized maxillary dental lamina; orange, specialized maxillary dental lamina that bears fangs. The specialized dental lamina is dilated into a bifurcated epithelial sac, the lateral part giving rise to the venom duct and venom gland by growing rostrad, then turning caudad to reach the post-orbital region. In Elaphe obsoleta (a–c) and Natrix natrix (data not shown), fangs develop rostrally and caudally alongside the base of the venom duct; in Naja siamensis (d–f) and Trimeresurus hageni (g–i) the rostral part regresses, remaining visible only as the dental ridge, whereas in b and c this part bears fangs and fuses with the anterior dental lamina. The unspecialized dental lamina in E. obsoleta (a–c) and the outgroup Liasis mackloti (j–l) starts developing anterior and grows caudad.
Now hang on, you may be thinking, if all the fangs develop at the back of the jaw, how do they end up out front in the front-fanged snakes? We can find the answer in development, too. Remember that the two tooth generating zones, front and back, are independent, and the front one can be repressed without disturbing the development of the posterior zone. In the front-fanged snakes, the anterior part of the upper jaw lacks sonic hedgehog expression, and the posterior teeth move forward naturally as part of the allometric expansion of the jaw in embryonic growth. This is sweet: not only does development reveal a homology, it also exposes the process that led to a morphological difference.
Here is the authors' summary:
Our results suggest a new model for the evolution of snake fangs. A posterior subregion of the ancestral tooth-forming epithelium became developmentally uncoupled from the remaining dentition, resulting in posterior and anterior dental laminae that are developmentally independent. This condition is retained in the non-front-fanged snakes, such as the grass and rat snake. This model would imply that the front-fanged elapids and viperids have independently lost the anterior dental lamina, which is supported by the lack of shh expression anterior in their upper jaws.
…
The developmental uncoupling of the posterior from the anterior tooth region could have allowed the posterior teeth to evolve independently and in close association with the venom gland. Subsequently, the posterior teeth and venom gland could have become modified and formed the fang-gland complex--an event that underlies the massive radiation of advanced snakes during the Cenozoic era.
The key innovation in snake evolution was a subtle one, an uncoupling of two tooth-generating regions that opened the door to more flexibility in the modification of the jaws. The fang/venom gland complex probably evolved once in the common ancestor of these groups, but the elapids and vipers independently stumbled on a secondary change, the suppression of the anterior region, that allowed the posterior fangs to move forward to make a more effective poison delivery system.
Vonk FJ, Admiraal JF, Jackson K, Reshef R, de Bakker MAG, Vanderschoot K, van den Berge I, van Atten M, Burgerhout E, Beck A, Mirtschin PJ, Kochva E, Witte F, Fry BG, Woods AE, Richardson MK (2008) volutionary origin and development of snake fangs. Nature 454:630-633.
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Ooh, PZ, I just love it when you talk biology! Seriously, thank you for yet another fascinating item.
Does this affect the story of Adam and Eve?
Octopus loves Mr. Potato Head
No, it's still completely wrong as history and science.
PZ has been one upped! :O
http://www.catholicleague.org/release.php?id=1468
It's a big confusing:
It's a big confusing what?
Dang fangs. I love the name Sonic Hedgehog :)
#5 : a play about virgins and biscuits...
I'd be curious as to what evolutionary circumstances led to the development of such a thing as a fang to begin with? I have no trouble grasping the evolutionary development of the eye (or in this instance teeth) but how and why did the simultaneous circumstance of a perfect injection machine and poison sac come to pass? There must be some scientific speculation someone could enlighten me about.
Enjoy.
#5, don't you mean he was upstaged? Badumpbump
O Sonic Hedgehog, is there no process in which you are not involved, nothing in which your expression is not enlightening?
Segmentation. Some folks were trying to push a role of Hedgehog in segmentation a while back, but the prevailing opinion now is that it's not doing much.
The evolution of venom preceded the evolution of fangs. Venom probably started with the expression of intestinal digestive-enzyme genes in saliva. Such venom can be delivered by ordinary teeth by a bit of chewing (ev4er been bitten by a racer or a watersnake? Gila monsters do it too). That sets up selection pressures for improved (nastier) venom and a more efficient delivery system (fangs).
I could back most of this up with references if I wasn't so damn lazy.
>I'd be curious as to what evolutionary circumstances led to the development of such a thing as a fang to begin with? I have no trouble grasping the evolutionary development of the eye (or in this instance teeth) but how and why did the simultaneous circumstance of a perfect injection machine and poison sac come to pass? There must be some scientific speculation someone could enlighten me about.
----------------------
The origin and evolution of the snake venom system has been long been an area of great controversy and acrimonious debate. It has only become recently evident that venom is a basal characteristic of the advanced snakes. All share a common ancestor that had venom glands but used ordinary teeth to chew the venom in. Many lineages independently enlarged the rear-teeth, an improvement but not a spectacular or difficult to achieve one. The true innovation in venom delivery came with the development of hollow-syringe fangs to deliver the venom in a high-pressured manner.
Logically venom preceeded fang as there cannot be a selection pressure for the evolution of intricate delivery systems in the absence of something worth delivering. Fangs and larger venom glands arrived much later,such innovations allowed the snakes to envenomate new prey items, such as being able to efficiently get past the thick fur of mammals or puncture the hard scales of other snakes.
All snakes with hollow front fangs were initially considered to all share a common ancestor but genetic evidence showed that this was not the case. Hollow front fangs instead evolved independently on three separate occasions. Thus a major unanswered riddle was how did they each innovate their arsenal. The natural 'intelligent design' of these unique adaptations has been unravelled for the first time.
This study is a perfect example of the inherent beauty of science, where even a failure can actually lead to an unexpected success. Initially we set out to study the unique glands of the night adder, an African snake with the largest venom glands in the world, massive glands that extend a quarter the length of the body. We bred the snakes to provide eggs to study the developmental genetics of the glands. However, reptile embryos are already partially developed at the time the eggs are laid. Developmental genes are turned on for only a very short period of time. Think of them as the first domino in a long series. The genes for the glands had already been turned on and then off before the laying of the eggs. So that study was a complete bust. However it turned out that we still had plenty of time to study the fang development.
As the venom system is an intricate combined system, a better understanding of one part facilitates the study of the other components. So the implications of this study go well beyond being a clever dental exam.:D
"but how and why did the simultaneous circumstance of a perfect injection machine and poison sac come to pass?"
I'm guessing completely, but sharp pointy teeth=goodness and poison glands=goodness, both give a selection advantage. Mutating the two together is double-plus goodness though.
-4
Now I have Frank Zappa's song Baby Snakes stuck in my head!
Here are some relevant references to venom preceeding fang. It is of course just sheer wonderful coincidence that they are my papers :D :D :D
Fry BG, Scheib H, van der Weerd L, Young B, McNaughtan J, Ramjan SFR, Vidal N, Poelmann RE, Norman JA (2007) Evolution of an arsenal: structural and functional diversification of the venom system in the advanced snakes (Caenophidia). Molecular & Cellular Proteomics 7(2):215-46
Fry BG, Vidal N, Norman JA, Vonk FJ, Scheib H, Ramjan R, Kuruppu S, Fung K, Hedges SB, Richardson MK, Hodgson WC, Ignjatovic V, Summerhayes R and Kochva E (2006) "Early evolution of the venom system in lizards and snakes" Nature 439(7076):509-632
Fry, BG (2005) "From genome to 'venome': Molecular origin and evolution of the snake venom proteome inferred from phylogenetic analysis of toxin sequences and related body proteins." Genome Research 15:403-420
Fry BG, Wüster W (2004) "Assembling an arsenal: Origin and evolution of the snake venom proteome inferred from phylogenetic analysis of toxin sequences". Molecular Biology and Evolution 21(5): 870-883
Fry BG, Lumsden N, Wüster W, Wickramaratna J, Hodgson WC, Kini RM. (2003) "Isolation of a neurotoxin (alpha-colubritoxin) from a 'non-venomous' colubrid: evidence for early origin of venom in snakes. Journal of Molecular Evolution 57(4):446-452
Fry BG, Wüster W, Ramjan SFR, Jackson T, Martelli P, Kini RM. (2003) "LC/MS (liquid chromatography, mass spectrometry) analysis of Colubroidea snake venoms: evolutionary and toxinological implications." Rapid Communications in Mass Spectrometry 17: 2047-2062
Snakes freak me the eff out. *shudder*
Quid est Sonic Hedgehog?
At least what is it in this context? And how did it get that name? I know about the nintendo game.
@17, good, then leave them alone, but don't kill 'em. Being a kid in Florida, I used to go with my foolish friends and catch snakes, scorpions, vinegaroons, whatever. Water snakes in particular are very very aggressive.
I remember getting a snake book from the library, and ogling the B/W pictures all day. I never opened it again, as I had horrific dreams that night.
Ah, the reading of hardcore science before my second cup of coffee. My thanks to PZ for his clear explanation for us non-biologists, and to Dr. Fry for his follow-up.
Doc Brian, you have a cool job. I grew up near the Other Melbourne (Melbourne HS '80). That's where I caught snakes.
A friend of mine kept a Massassuaga for a while. He took it in a mayo jar to release it. As soon as it poked it's head out, it whipped around and struck him on the arm. Careful with those biters, they have no sense of gratitude.
#5.) PZ has been one upped! :O
Don't agree. It is just a play about crackers.
I would say that Bill Donohue is a snake, but he is harmless as he has no venom.
Lynnai, for those of us without strong science backgrounds, the Wikipedia articles on Sonic Hedgehog and Hedgehog signaling pathway appear to be reasonable. Sonic (Sega, not Nintendo) is a whimsical name for a developmental pathway that relies on genes of the same name to help cells within organisms differentiate properly during development.
Any mistakes in understanding are mine.
so whats the REASON for the venom to 'evolve'?
GOD!!!!!
you seriously think this just randomly happened? or that 'evolution' (your god) was thinking it needed it and 'evolved' it ....
i love seeing evolutionist talk nonsense, it makes the creation all so much easier to see.
thank god for living in a country where the majority accept gods creation. maybe you should move to soviet union or europe and see how fun they have it there.
As noted by others, it wasn't simultaneous, but they used their teeth to get the venom past the blood barrier. What I don't think was mentioned is that there are various kinds of tooth delivery of venom, ranging from grooves in teeth, to the wonderful hollow fangs of rattlesnakes and other pit vipers.
The point I'm making with that is that there are (currently) stages intermediate to unmodified teeth, to hollow fangs. Presumably the grooves became more efficiently connected to the venom ducts, and became more and more close to being fully enclosed by the tooth. At some point the grooves simply became enclosed, and you then had your hollow fang injection system.
Indeed, when you see something that looks too difficult to evolve because of the problem of all of the simultaneous changes that have to occur, look around to see if they really need to be simultaneous. In nearly all cases, they do not have to be.
Glen D
http://tinyurl.com/2kxyc7
(.)(.)
>Doc Brian, you have a cool job.
I reckon so too :D
I am actually currently kicking back at a tropical beach in Colombia taking a break from catching snakes here. Its a dirty job but someone's gotta do it! :D
Did Kent just ask people to move to a non-existent country? Bit behind the times, no?
Oops, should have proofed it. Here's the correction I need to make:
Glen D
http://tinyurl.com/2kxyc7
no, natural selection was involved
NOT
nnoooo...
Yes! Bring the stoopid! have a nice deluded life, Kent.
I don't love seeing creationist morons talking nonsense because they don't know the first thing about what evolutionists actually say (let alone have any intelligent objections to it).
Natural selection is not random. See if that simple fact can stick to your thick skull.
Glen D
http://tinyurl.com/2kxyc7
One more thing, Kent.
How about telling us how and why "God" chose to design venom systems that have killed so many of his "children".
Then write to Behe and tell him how malaria is a purposeful arrangement of parts (as he defines design to be). It would be interesting, because he has never explained anything with respect to design, yet tells us that Plasmodium falciparum was designed. It just doesn't fit his definition of design, nor does snake venom.
IOW, we're still waiting for a coherent ID hypothesis, let alone one that has evidence in favor of it.
Glen D
http://tinyurl.com/2kxyc7
I swear, I get all giggly when one of the study's authors actually drops in to give us a Special Feature Behind The Scenes.
Also, what about vampires?
Kent, your comments are idiotic. Go get a book on evolution & read it before shooting your big mouth off.
You could read Darwin's "On the Origin of Species...", just to see how simple an idea evolution by natural selection really is, when you put all the components together as Darwin & others did in the mid-nineteenth century. It was an idea whose time had come, and Darwin put in arguments that have stood the test of time, & been verified by subsequent research in genetics, etc.
There has been nothing to refute the theory of evolution by natural selection.
You've been conned by religious leaders. There aren't any gods.
Kent blathered
>so whats the REASON for the venom to 'evolve'?
>GOD!
HAHAHAHAHAHAHAHA
That statement is so ridiculous I don't even know where to start. So God caused an invasion of snakes from Asia to Australia once Australia drifted close enough? Resulting in a massive diversification of the lineages and unique changes in the venom? God caused the egg-eating sea snakes to start losing their venom as they no longer needed it for prey capture? We even have transitional forms in the Australian Brachyurophis genus of Shovel-nosed snakes where some feed on lizards, some on lizards and lizard eggs while others specialise on just lizard eggs. The latter have atrophied venom glands relative to the former.
Wow. I just love how after scientists bust their butts in the lab for years to answer a riddle, it is always dismissed with the catch-all 'Guddit'. That is infantile logic at its finest. We are studying modern uses of ancient toolboxes. As oppossed to recently evolved tools such as yourself. Go back and play in your sandbox and I hope the cat crapped in it! :D
Maybe you should move to a state where they have a school system? Then you wouldn't be nearly illiterate and ignorant.
1. gods creation should be god's creation. And usually fanatics capitalize god as God, proper name and all.
2. The Soviet Union collapsed a decade ago. It doesn't even exist. To move to the Soviet Union, one would need a time machine. Communism collapsed also. You need to update your list of things to be frightened of.
3. The standard of living in Europe is as high or higher than the USA in most countries. The crime rate is generally much lower, educational levels are higher, and social problem rates are lower. Many Americans live in Europe by choice. More would but the Europeans have a problem with illegal migrants from the US. They keep sneaking across their borders to take low wage jobs from the natives.
"... maybe you should move to soviet union or europe and see how fun they have it there."
Umm, have you ever been to any part of Europe?
Wait, what am I saying? Of course not. Nevermind.
James W (in London, in Europe)
#24
"so whats the REASON for the venom to 'evolve'?
GOD!!!!!"
Oh! Kent! Is that you? Did they let you out of jail already? Hmm, I can understand that. Even jail wardens must get tired of your preaching after a time.
Oh, by the way, did you know there's no more Soviet Union? I'm sorry I have to break the news to you. I know how hard it can be to live without an arch-villain to hate. But I see you still have godless Europe, so it should be ok. By the way, it's where I live and, yes, it's rather nice. Myself, when I read the news about this or that crazy religious bigot in the US, I'm glad there's an ocean between us. Well, I'm not so much worried by the existence of the crazies than by the fact that they're sometimes backed by local authorities, police forces, military officers, even the government. That's pretty bad.
And did you know that evolution doesn't "think"? It's not an entity, you know, like your god. It has no thoughts, and no beard too. It's just a natural process with certain properties. Sure, creation is much easier to understand. Fairytales generally are easy to grasp. You can dismiss evolution as "nonsense", but it just goes to show that you haven't a clue about what it is. But there are so many books explaining it clearly! Why don't you try to read one or two? Go on, learn, and then come back later and we can discuss...
>Also, what about vampires?
Do vampire bats count? One of the things I am doing down here is comparing the evolution of vampire bat anticoagulants. There are three genera (each monotypic)
- one specialises on mammals
- one specialises on birds
- one prefers birds but will take mammals
The first two have anticoagulants that hit perfectly their respective prey blood coagulation systems. The coagulation cascades are not identical so this is key to how the third one affects both birds and mammals but not a efficiently a either of the specialists. We are seeing how they overcome the differences in the prey blood.
We use virginal maidens as bait. In short supply around here though :D :D :D Although I am funding my research by having a 'second hand virgin shop' with half off all slightly used merchandise. :D :D :D
Dr Fry,
Thank you very much for commenting on the post during your holiday. An absolutely fascinating read!
Too cool, thank you PZ and a special thanks to Dr. Fry for his very enlightening additions. I am amazed at the stunning coincidence that all the papers cited by Dr. Fry were also authored by him. I also think w owe him a debt of gratitude for all the grueling field work he does, don't forget the sun tan lotion Dr Fry.
My only problem with the post was that the hue of green & orange used in the diagram was to a partial color blind person such as myself totally indistinguishable.
Kent, congratulations you manged to be wrong in every sentence. That has to be some sort of record
"but how and why did the simultaneous circumstance of a perfect injection machine and poison sac come to pass?"<\i>
See some nice pictures of how a hollow fang that can inject poison is simply a tooth that folded back over a poison-delivering groove
http://www.austmus.gov.au/factsheets/snake_fangs.htm
Back in 1950, Karl Schmidt published Modes of Evolution Discernible in the Taxonomy of Snakes in Evolution, Vol. 4, No. 1 (Mar., 1950), pp. 79-86
http://www.jstor.org/stable/2405535
He talked about how snake venom is basically just elaborated digestive secretions, and how hollow fangs are folded-back teeth. It is interesting to read his phylogenetic speculations in light of the latest findings.
Once you've got a longitudinally enrolled tooth with some nifty nasty chemicals trickling down it, it isn't much of a trick to increase the secretions and develop a holding sac and some muscles to squeeze the poison into the fang.
@Tim Fuller #9
I've read in some book (I'm pretty sure it was Wonderful Life) that the armors of the (plated) burgress shale fishes were not bony but toothy. And it seems that a bit before that some kind of sea-worm with bizarre toothy structure is found in the fossil record (one of the first animals with solid parts). So I guess the circumstances were first "feed" (lamprey like, or maybe by simply being a more efficient killer worm), and actually arose before the appearance of bones.
@Confused #11
I'm pretty sure I read (on pharyngula even, when there was all that hubhub about the platypus' genome decoding) that snake (and platypus) venom come from immune system proteins (β-defensins), not intestinal ones.
See http://scienceblogs.com/pharyngula/2008/05/the_platypus_genome.php
It didn't occur to me that kent could be Kent Hovind but the resemblance is uncanny. I didn't know they had internet access in the federal prison system.
Doesn't look like the diploma mill Ph.D. was worth much.
Careful with those biters, they have no sense of gratitude.
And how would *you* feel about being stuffed in a mayo jar?I know my little garter is very unhappy about cage cleaning time.
In fact the garter is a perfect example of what we were talking about... it has slightly venomous saliva, but no delivery system except chewing. On the small prey items that it feeds on it keeps the prey from struggling too much during swallowing, and helps them avoid injury.
Oh, the venom is related to other colubrid venoms and garters have rear fangs, too.
>I'm pretty sure I read (on pharyngula even, when there was all that hubhub about the platypus' genome decoding) that snake (and platypus) venom come from immune system proteins (β-defensins), not intestinal ones.
The origin of venom proteins is actually much more widespread than that. What has to be stressed however is that absolutely none of them are modified saliva proteins. This is because the reptile venom gland, for example, is not a modified saliva gland. It is an entirely new structure with no homology to anything elee out there.
Venom systems are a key evolutionary innovation and have arisen independently in divergent animal lineages. The most extensively studied venoms are from the medically-important snakes (atractaspidids, elapids and vipers), yet venom systems are also present in other lineages including lizards, mammals (e.g. Platypus and Slow Loris), teleost fish (e.g. Catfish, Stonefish), cartilagenous fish (e.g. Stingrays, Port Jackson Shark, Chimera), molluscs (e.g. Octopus, Cone Snails), cnidarians (e.g. Blue-bottle, Box Jellyfish), echinoderms (e.g. Crown of Thorns Starfish, Flower Sea Urchin) and \several arthropod lineages (e.g. Centipedes, Scorpions, Spiders, (example) and (example). Modes of venom delivery are equally diverse and include barbs (e.g. Stingrays), beaks (e.g. Blue-ring Octopus), fangs or modified teeth (e.g. Centipedes, Water Shrews, Snakes, Spiders), harpoons (e.g. Cone Snails), nematocysts (e.g. Box Jellyfish), pinchers (Pseudoscorpions), proboscis (Assassin Bug), spines (e.g. Catfish, Port Jackson Shark, Stonefish), spurs (Platypus) and stingers (e.g. Ants/Bees/Wasps, Scorpions) indicating considerable morphological innovation in the evolution of venom systems. Furthermore, the use of the venom ranges from defense to predation (or a combination of both) and sites of action include virtually all major physiological pathways and tissue types reachable by the bloodstream (e.g. Fry 2005).
We have shown that venoms evolve via a process by which a gene encoding for a normal body protein, typically one involved in key regulatory processes or bioactivity, is duplicated and the copy selectively expressed in the venom gland. The proteins recruited range from all over the body includig blood, antimicrobial and even brain neurotransmitters. The newly created toxin type evolves via the birth-and-death model of protein evolution, in which a toxin multigene gene family is created by further gene duplication events followed by the deletion of some copies and conversion of others to non-functional copies or pseudogenes. As a result paralogous groups of genes are generated across taxonomic lineages where the gene duplication event occurred prior to their divergence. These evolutionary patterns are similar to those observed for multigene families involved in the adaptive immune response such as immunoglobins and major histocompatibility complex genes, a process which is thought to contribute to an organism's ability to react to a wide range of foreign antigens. In an analogous manner, animal venom toxins must react with diverse compounds in their prey. The birth-and-death model of protein evolution generates suites of toxins that allow the predators to adapt to a variety of different prey species.
The newly created toxin multigene families preserve the molecular scaffold of the ancestral protein but modify key functional residues at the tips of loops to acquire a myriad of newly derived activities. These toxins have an unusual combination of precise specificity and extreme potency, characteristics that make them particularly amenable for use as investigational ligands or as leads for drug design and development. An early example of this is the development of an ACE (Angiotensin Converting Enzyme) inhibitor drug, Captopril, based upon a small snake venom peptide (teprotide). This and other related peptides contained a tri-peptide sequence (Phe-Ala-Pro) upon which the side chain interactions with ACE were modeled. This discovery led to the creation of a multibillion dollar drug class based upon a snake toxin. More recently, the applicant has filed a patent application for the use of novel venom natriuretic peptides in the treatment of congestive heart failure. Showing how human medicine benefits from study of evolution. However if the happy-clappys still insist on rejecting evolution, then they cannot benefit from the fruits of the labour. Enjoy your aneurism dickhead.
Despite this extraordinary diversity in the structure and function of animal venom systems, several protein groups have been independently recruited for use as venom toxins in multiple lineages. These include CAP proteins [CRISP, Antigen 5 (Ag5) and Pathogenesis-related (PR-1)], Peptidase S1, PLA2 (phospholipase A2), natriuretic peptide and kunitz peptides. CAP proteins have been independently recruited for use as a toxin by reptiles, stinging insects (Hymenoptera) and cone snails and is a major allergenic protein in saliva of hematophagous insects. Natriuretic peptides have been recruited into the venom of the platypus, and into reptile venoms. The PLA2 and kunitz peptides have been recruited in disparate lineages, being present in the venoms of reptiles, cone snails and insects. They are also one of the major toxin types secreted by toxic arthropods that are blood meal specialists (such as ticks). The recurrent recruitment of homologous venom toxins across this taxonomic spectrum suggests structural or functional constraints on the evolution of animal venom.
What I am working on now is a general theory of how venom evolves. New insights into the evolution of venom systems and the medical importance of the associated toxins cannot be advanced without recognition of the true biochemical, ecological, morphological and pharmacological diversity of venoms and associated venom systems. A major limitation of the study of venom proteins has been the very narrow taxonomical range examined. As a consequence, several major animal groups with known or suspected venom systems have remained largely unexplored. The mollusc lineage Cephalopoda (including squids, cuttlefish and octopuses) is one such major clade. With approximately 800 known species, cephalopods represent an important element in marine trophic systems worldwide, displaying an impressive variation in shape, size (from 2 cm to over 10 m) and habitat (benthic to abyssal, tropical to Antarctic). So I am currently collecting specimens from all ecotypes. I was in Antarctica this year and got 254 specimens, including two giant octopuses. After I am done suntanning in South America I will be in Asia enjoying dim sum while collecting octopuses there.
Cheers
B
maybe you should move to soviet union or europe and see how fun they have it there.
Just awful. Actual 36-40 hour work weeks, 27 paid days off a year (and sick days don't count against that), affordable health care, affordable schools, public transportation that gets you somewhere, representative democracy...
Awful.
Thanks, greatly, Dr. Fry for your additional information.
From snake venom to the virginity of bats in 40 posts. Yes, this is a day for giggling!
Somewhat OT, but clearly an issue related to this and the various "Kents" of this world who prefer story-telling to science. And more important than any old crackers, btw. Bleeding Kansas still has to contend with yahoos opposed to science, and it's quite an issue right now:
Science is limited, Martin. That's why it's called "science", not "whatever you want". It follows the rules of evidence, and pays heed to what is known about causation and regularity.
Wait till Hinduism is being taught in science class. You'll suddenly realize that science is limited to proven methods and to realistic inferences, and is not a vehicle for spreading unfounded myth.
Anyway, there's no telling what will be in Kansas after the election.
Glen D
http://tinyurl.com/2kxyc7
Very interesting information there, Dr. Fry.
Glen D
http://tinyurl.com/2kxyc7
But not "Ontogeny recapitulates phylogeny", right? :P
This just keeps getting better and better. First a great post on the evolution of fangs in snakes with comments from one of the authors, then a quick excursion into vampire bats and now a overview of the evolution of venom's in general. I love me the science posts.
Dr Fry, you do have one of the coolest jobs in the world. Could you use the help of an aging trans-women who's Biology degree is far in the past but who is very good with computer networks?
Neat! Looking at the phylogeny, I see that 'Colubridae' has finally been split up; I've heard for the longest time that it's paraphyletic. But where do the bizarre side-stabbing atractaspidids fit in?
[Never mind: this link indicates that they're related to the lamprophiids (or boodontids?), and these two are in turn related to the elapids. Or wait, are the atractaspidids considered part of the lamprophiids in this Vonk et al. (2008) study?]
I was also not aware that ALL the former 'colubrids' possessed proper fangs.
Dr. Brian Fry was also involved in the study that discovered the prevalence of venom in many lizards as well:
http://en.wikipedia.org/wiki/Toxicofera
So the use of venom was probably already widespread among lizards*, including those ancestral to snakes. My guess is that it would have been used to subdue prey (like the Gila monster?), or to start the digestion process in the mouth, or even as an added 'kick' when biting in self-defence when threatened by a predator.
*lizard is used here as a layman's term, because after all, snakes are a highly specialised and diverse lineage of lizards.
If this is the case, then I am also wondering if the more basal snakes like typhlopids, aniliids, boids and pythonids, acrochordids, xenopeltids etc. actually lost their venom glands, or whether they possess weak venom.
It would be nice to see if the other venomous rear-fanged 'colubrids' from the other families such as Homalopsidae are also examined to see if the development of the fangs is the same.
Dr. Fry: I had no idea the egg-eating sea snakes had lost their venom! (Are you referring to Emydocephalus?)
Awesome! Thanks for the extra details and the background info, Dr. Fry!
In case anyone is interested in what an Antarctic giant octopus looks like, here me with one of first of the two specimens.
http://www.venomdoc.com/images/Bryan&giant_octopus.jpg
As you can tell by my grin, I am rather pleased in a very White Hunter sort of way! I didn't even know that Antarctica had giants until the that one came up in the nets!!
Sir sir please sir!
Can we have one on jellyfish venom ere long? Especially these weird killer jellies whose toxins are so damn deadly, in such tiny amounts, I assume they must be catalytic somehow.
CD
(pants expectantly)
# 37
(in London, in Europe)
lol. way to bring it down to their level.
i for one would love to live in London. at least i would have decent health care.
#24
argument boils down to... I don't understand this. Therefore it is nonsense. Therefore the explanation I do understand is better. Therefore the explanation I do understand is true.
flawless logic.
I don't mean to dis biology... but I'm more of a sociology/social psychology kindof guy. Just wanted to know if neone knew of anybody like PZ who was blogging on peer reviewed sociology articles?
This work shows us the wonderful integration of species divergence in the genes, in the development of morphologies and in the rocks of our world. Science at its finest, explaining the story of life and of course us! What is so scary about this to some humans? Why must they cling to this skyhook they call god?
Rather than continually ridiculing them, how about if we try to explain their responses? Dennett's DDD and "Breaking the Spell" suggest wonderful evolutionary tools to help us study and understand these believers in gods. Let's extend the key evolutionary idea: "Everything is the way it is because of how it got that way," to the religious. Maybe these gods actually exist: as powerful and effective memes, infecting minds, turning the hosts (the other kind) to machines for spreading and infecting others. Let's put these believers under our microscopes and naturalize them.
Thereby neutralize them.
The Naturalist.
Thanks Bryan for your commentary and response. I particularly liked this sentiment:
As for my "ungrateful biters" remark, even though the mayo jar was only for transport, I told my friend he deserved it and was a dumbass. I'd have bit him, too, FFS. 2 weeks of horse serum and home from school wasn't punishment enough.
>Neat! Looking at the phylogeny, I see that 'Colubridae' has finally been split up; I've heard for the longest time that it's paraphyletic.
Yep, they were a taxonomical dumping ground for anything that wasn't obviously a elapid or viperid. Based of course on cursory morphological studies. Its all being properly sorted by genetic studies. DNA is everything, the rest is just details! :D :D :D
>But where do the bizarre side-stabbing atractaspidids fit in?
They are distinct from the elapids, no question of that, and ditto with the viperids. They represent the third evolution of hollow-front fangs.
>[Never mind: this link indicates that they're related to the lamprophiids (or boodontids?), and these two are in turn related to the elapids. Or wait, are the atractaspidids considered part of the lamprophiids in this Vonk et al. (2008) study?]
The phylogeny is stable. The relative naming of higher order relationships is a matter of philosophy: whether to lump or split. Lumping keeps the shared evolutionary history obvious while splitting recognises unique derivations.
>I was also not aware that ALL the former 'colubrids' possessed proper fangs.
They don't. Have a look at our 'Evolution of an Arsenal' paper for the insane dentition diversity.
http://www.venomdoc.com/downloads/2008_BGF_Evolution_of_an_Arsenal.pdf
All the variants are there that you'd expect to emerge with active evolutionary tinkering.
>Dr. Brian Fry was also involved in the study that discovered the prevalence of venom in many lizards as well:
http://en.wikipedia.org/wiki/Toxicofera
Yep. That was a fun study. Anytime I get to mess with komodo dragons is a good day! So much for the 'toxic bacteria' hypothesis of komodo dragon bites!!!
>If this is the case, then I am also wondering if the more basal snakes like typhlopids, aniliids, boids and pythonids, acrochordids, xenopeltids etc. actually lost their venom glands, or whether they possess weak venom.
Watch this space. We are actually writing up exactly that study right now!!
>It would be nice to see if the other venomous rear-fanged 'colubrids' from the other families such as Homalopsidae are also examined to see if the development of the fangs is the same.
Live-bearing lineages are going to be nightmares to study in this regard.
>Dr. Fry: I had no idea the egg-eating sea snakes had lost their venom! (Are you referring to Emydocephalus?)
and Aipysurus eydouxii as per two of our other papers:
Li M, Fry BG, Kini RM (2005) "Putting the brakes on snake venom evolution: the unique molecular evolutionary patterns of Aipysurus eydouxii (Marbled sea snake) phospholipase A2 toxins." Molecular Biology and Evolution 22(4):934-941
http://www.venomdoc.com/downloads/2005_BGF_Aipysurus_eydouxii_PLA2.pdf
Li M, Fry BG, Kini RM (2005) "Eggs only diet: the shift in preferred prey by the Marbled sea snake (Aipysurus eydouxii) resulting in a loss of postsynaptic neurotoxicity." Journal of Molecular Evolution 60(1):81-9
http://www.venomdoc.com/downloads/2005_BGF_Aipysurus_eydouxii_3FTx.pdf
Cheers
B
@#19: Man, I can't even look at a snake. I had to fold over any pictures of snakes in biology textbooks in school so I wouldn't see or touch them.
The study is pretty cool though, as long as I don't have to see pictures.
i understand this very well, you get indoctrinated into believing in your evolution god, so you do no longer need to accept the consequences of your actions. hitler, stalin, mao, you name it.
OF COURSE i dont know or been anything, i accept the grace of god, SO OBVIOUSLY i know nothing.
and i have BEEN to europe, i SEEN how 'nice' they have it there. and I AM HAPPY to be AMERICAN and glad to get back to this wonderful country of ours and thankful for everything we have. internet? cars? airplanes? the best heathcare system in the world? the best military in the world? microsoft? oh, and what are you using now mr london? a COMPUTER? the INTERNET?
and maybe you have a cellphone there to?
GOD BLESS AMERICA
I never even got to ask the question, and it was answered. I was wondering where the spitting cobra came into this. I see now it is an earlier developed evolutionary model (unless I misunderstood all that I read).
>Can we have one on jellyfish venom ere long? Especially these weird killer jellies whose toxins are so damn deadly, in such tiny amounts, I assume they must be catalytic somehow.
I assume you are referring to Irukandji jellyfish? They are another perfect example of evolution. They live on the reefs, where long tentacles and big bells would be catastrophic. So instead they have tiny tentacles, small bells and have the stinging cells concentrated on the bell instead of the tentacles. The venom hits the heart about 20 minutes after a sting, producing effects very similar to a heart attack. I remember we were dive collecting one time on the barrier reef. On the first dive of the day, someone in another group had a heart attack. He was a bloke in his late 30s and it was an easy drift dive with an 18 meter bottom. I reckon he got smacked by an irukandji-type. The reason I say 'type' is that it appears there are multiple species. One mate of mine was going to name one after his ex-wife, calling it Carukia angelinii. Describing the envenomation as a 'short but painful experience'. Ironically, he found that treating the envenomation was the same as treating the divorce, lots of amber antivenom (beer) seemed to do the trick nicely :D :D :D
>accept the consequences of your actions. hitler, stalin, mao, you name it.
To quote the Big Lebowski 'That like your opinion dude'.
To see dodging of responsibility, one has to look no further then the slimey church dodges at responsbility for their well-established networks where juicy young altar boys are traded like baseball cards by the pedophilic priests.
Hi Kent, could you take a moment to explain why the abortion rates are so low in evil secular northern Europe compared to the godfearing US? You'll get bonus points for including the crazy high numbers of abortions in countries where the catholic church holds sway in middle and southern America (almost double of evil secular Europe).
Thanks Kent.
An early example of this is the development of an ACE (Angiotensin Converting Enzyme) inhibitor drug, Captopril, based upon a small snake venom peptide (teprotide). This and other related peptides contained a tri-peptide sequence (Phe-Ala-Pro) upon which the side chain interactions with ACE were modeled. This discovery led to the creation of a multibillion dollar drug class based upon a snake toxin. - Dr. Brian Fry
I've been swallowing my daily Enalapril for years without knowing that. Please pass on my thanks to the snakes and herpetologists concerned if you get the chance!
>I never even got to ask the question, and it was answered. I was wondering where the spitting cobra came into this. I see now it is an earlier developed evolutionary model (unless I misunderstood all that I read).
Spitting cobras are simply additional refinements within the elapid lineage. Spitting has been derived on three occassions: Asian and African Naja species have done it independently as has the Hemachatus genus.
While the spitting cobras are the pride of the elapid family, the drooling cobras are the embarassment! :D
Cheers
B
Wrong from the very first two words on, kent. I'll bet you don't even know your bible.
Indoctrination indeed.
Dr. Brian Fry: Thanks for the info!
And oh yes, I'd completely forgotten that homalopsids were live-bearing! Damn.
The paper on how fangs have evolved (and been reduced) multiple times is extremely fascinating. Particularly interesting how egg-eating snakes appear to be close relatives of the venomous cat snakes.
Will you happen to drop by Singapore in your quest for cephalopods? You seem to have done quite a fair bit of work with the Singapore Zoo, and I do remember how you were featured in a mini documentary series on the Singapore Zoo that was shown on the regional Animal Planet a few years ago.
>Will you happen to drop by Singapore in your quest for cephalopods?
Probably not. I was just back there a couple months ago. I'll be in Hong Kong, mainland China and Malaysia.
Cheers
B
Has there been any hypothesizing on why venom isn't more prevalent amongst all predators? If venom development is truly a low-cost / high-benefit solution with ample pathways of gradual evolution, it seems that any common predator (wolves, sharks, pirrhana, you name it) that could use a little extra "stun" power against their prey should have developed it.
So, is there something about these predators which magnifies the cost or decreases the benefit that venoms might deliver? Or, alternatively, is there something about the original venomous ancestors of today's venomous species which magnified the benefit or decreased the cost of venom evolution?
Chris (@ Mixing Memory) wrote "But Seed's biggest blog [Pharyngula], the one to which everyone else in the network is inclined to link if they want a traffic boost, and which therefore can have a big influence on the content of the entire network, long ago ceased to be about either science or conversation."
In your face, Chris!
Thanks PZ for the great post, and thank you too, Dr. Fry, for participating in the comments. Fascinating and informative.
>If venom development is truly a low-cost / high-benefit solution
Actually, as the Evolution of an Arsenal paper + the two egg-eating sea snake papers show, it is actually a high cost solution. It is basic biochemistry: it takes 4ATP molecules to join one amino acid to another. So the energetic cost of producing multi-milligrams of protein is quite high. This creates a use it or lose it selection pressure. Venom is an early evolving characteristic in just about every higher order lineage but has been secondarily lost in some derived lineages with new adaptations such as increased bite force or vegetarian diets as examples.
Bryan, that pic looks like you're prepping a Feast For The Ages.
Again, thanks for posting here. Very interesting about all the venoms and envenomation techniques. When I studied it in HS, nematocysts were believed to be fired by contact with CO2. Is this still so? What thoughts are there about evolution of their venoms (kind of hard to find them in the archaeological record) and commonality among them? I'm interested in a lay way, in the range from "non-stinging" to irukanji, and to Physalia - i.e. range of toxicity, relationship wrt very different body types.
I think Kent is a parody, he can't be real, just can't be.
I score that a 6 out of ten.
On content it score higher than 6 but not much. It has the typical bullshit about Hitler and the ignorance on Stalin and Mao, the Cock waggling patriotic Euro hating, the rambling from point to point seemingly with no connection. But there is little creativity.
But It scores low on the technical scale. He only uses odd capitalization (or lack there of) and odd punctuation with some strange substitution of "i" instead of "I've" and disjointed lists of words.
But where are the BOLD and the ITALICS or even the BOLD ITALICS? And I think some more random scare quotes and misspellings would better support him as a bona fide winger.
I think you can do better Kent. I'm pulling for you next round.
#33 StuV said:
There is a tremendous amount of controversy as to whether or not vampires and other undead supernatural creatures are subject to the same selection pressures as living organisms. After all, they're dead. And reproduction, as such, is very slow.
On the other hand, they're up walking around, so, I dunno, maybe prehistoric vampire ancestors went around chewing necks instead of biting them, and there was selective pressure to develop a more efficient blood-feeding system. Fangs would also allow for more precision in hitting the jugular on the first bite.
BigDumbChimp,
The fact that he hasn't used html formatting tags should score him higher on your scale not lower. As to show some proficiency in the use of technology would naturally make him less of a winger. Everything else I agree on though.
Good point. I'll take that into consideration next round. However there are high quality trollers than are at least somewhat proficient in the basics of bold and italics purely because they think it better pushes their rambling incoherent points across, that or it adds style.
...and EVERYONE knows that style is bonus points.
than = that
@69 Dr. Fry
In other words, I misunderstood all I read. But that only defines my screen name, 'cause I didn't understand any of the science you explained. That's OK, I love science even when I don't understand it. It still makes more sense then goddidit.
Go Shh! I saw this in Nature yesterday, and was just waiting for it to show up here.
You know, PZ, you do such a service to us. Even many individuals in Science, such as alot of the grad students I know, look at papers like this and say "yeah, and what does this have to do with me everyday life?". This is the exact comment I got yesterday when I brought up the subject of this paper. Thanks to you I am now much better equipped to say "it has everything to do with your everday life" and to tell them why. I love this stuff.
Basal snakes may not have true fangs, but some of them have enlarged teeth that sure do look and feel like fangs. The enlarged teeth help them grasp and hold onto prey. A large boa or python can give a seriously nasty bite, so please don't try to capture a large snake unless you have the training to do so.
Yes normally it is but in the context of the severity of wingness I would think that style shows too much organized thought. Better it be almost chaotic ramblings with no formatting and no style save what they can punch out with their 104 key extended keyboards.
The World Wide Web was invented at CERN, in Switzerland.
And I'm accessing it on a computer made by Sony, a Japanese company.
Yes, but that is a style all in its own. But point taken.
Yes I guess it is. It can't be easy disorganizing ones thoughts in such an incoherent way.
A Molly for Dr. Fry!
Dr. Fry,
Excellent writing, thanks for being here! Now a question regarding the Komodo Dragon and it's bacterial bite. I've inferred from your postings that this is NOT the case for the Komodo dragon, so I'm curious as to what is actually happening in its bite in terms of venom. BTW, in case you can't tell, I'm not a biologist :)
Thanks again!!
"Quid est Sonic Hedgehog?"
I was reading about this just last week. It's a gene that helps establish body layout.
In the early days of fruit fly genetics experiments, they found that a gene that when it's messed up the fruit flies develop a short bumpy curled up appearance, and so they named it the hedgehog gene. As more were discovered they started naming them after famous hedgehogs. There was Indian, Desert, Tiggywinkle, and then Sonic.
I HIGHLY recommend the book "Your Inner Fish" by Neil Shubin. It's only mildly technical, so non-biologists can read it. There is an excerpt at http://richarddawkins.net/article,2125,n,n
-Jeff
Like the Burmese pythons in Florida. Snakes don't bother me much. Large constrictors capable of eating alligators and humans do.
OK I'll bite, read this first.
http://www.photius.com/rankings/healthranks.html
then this.
http://www.alertnet.org/thenews/newsdesk/N07438178.htm
then get back to me on this one.
'microsoft'??? The mere fact that he include MS in this list shows complete and utter insanity to be the defining factor.
And, uh, computers? Invented in Yurp.
Internet? Look at how many europeans were involved (come to that, look at how many europeans are managers and leaders in sikicon valley) and obviously the web was invented by europeans.
Cars? mmmm.... oh yeah, mercedes-benz.
Airplanes? *possibly* americans.
America is a country with a short and interesting history including some great people and appalling mistakes. Europe is an agglomeration of wildly diverse countries with a long history including some great people and some appalling mistakes.
Here is a scientific hero. I guess Paul would think this guy is dumb since he believes in God. But that only shows that Paul is an idiot.
Francis S. Collins (born April 14, 1950), M.D., Ph.D., is an American physician-geneticist, noted for his landmark discoveries of disease genes, and his leadership of the Human Genome Project (HGP). He will be director of the National Human Genome Research Institute (NHGRI), one of the 27 institutes and centers that make up the National Institutes of Health in Bethesda, Maryland until August 1, 2008 (he announced his resignation on May 28, 2008).
Collins has described his parents as "only nominally Christian" and by graduate school he considered himself an atheist. However, dealing with dying patients led him to question his religious views, and he investigated various faiths. He became an evangelical Christian after observing the faith of his critically ill patients and reading Mere Christianity by C. S. Lewis.[6]
In his 2006 book The Language of God: A Scientist Presents Evidence for Belief, Collins considers scientific discoveries an "opportunity to worship." In his book Collins examines and subsequently rejects creationism and Intelligent Design. His own belief system is Theistic Evolution (TE) which he prefers to term BioLogos. BioLogos rests on the following premises:
1. The universe came into being out of nothingness, approximately 14 billion years ago.
2. Despite massive improbabilities, the properties of the universe appear to have been precisely tuned for life.
3. While the precise mechanism of the origin of life on earth remains unknown, once life arose, the process of evolution and natural selection permitted the development of biological diversity and complexity over very long periods of time.
4. Once evolution got under way no special supernatural intervention was required.
5. Humans are part of this process, sharing a common ancestor with the great apes.
6. But humans are also unique in ways that defy evolutionary explanation and point to our spiritual nature. This includes the existence of the Moral Law (the knowledge of right and wrong) and the search for God that characterizes all human cultures throughout history.
"Evolution is God's way of giving upgrades" (Stephen Colbert Interview, December 7, 2006)
I don't like the fat that even this thread is devolving......
Sam:
Francis Collins shuts off his brain whenever the subject of "faith" or "spirituality" comes up. We've been down this road before.
Typo: I don't like the fact that even this thread is devolving......
Wrong, Sam. Humans are related to every other living organisms on this planet, not just other primates. That's one of the coolest things. Every animal, every plant, they are your cousins. Many animal societies DO have moral codes (of course, the babble doen's mention that, because it's a friggin' bronze age fairy tale book).
Goddidit = I dunno
So Francis was living a crisis and leaned on a crutch. And now he has the answers to astrophysics and abiogenesis, as well as gene mapping?
Cognitive dissonance + narcissism = godbothering scientist
Francis Collins is brilliant in some aspects but makes some really stupid claims suspending the use of the tools of science he possesses in others.
But which category of snakes does VenomFangX belong to?
I learnd quite a lot from this article and the excellent comments. I grew up in an area of East Texas where you simply had to know some pretty good snakelore to walk safely in the woods and from what I've learned since, our snakelore was pretty accurate.
I was surprised to find that coral snakes are related to cobras and that the article said that like other Elapids, they were front fanged. This doesn't fit with local folklore about coral snakes. I was taught that the coral snake had powerful venom, but no fangs to deliver it and that one generally didn't need to fear it. Corals are extremely shy anyway and I've only ever seen one and for a time I went snakewatching regularly. So do North American coral snakes really have front fangs capable of delivering potent venom? Are there coral snakes in other parts of the world that do have front fangs even if local corals dont? Even if our local corals do have front fangs, we are still right to mostly not fear them. Their mouths are weak and small.
Still, if coral snakes have front fangs and are related to cobras, why aren't there any large and nasty cobra-like snakes in North Amerca? There are plenty of large and nasty pit vipers, so clearly there are niches for large venomous snakes. Did the vipers just get here "the firstest with the mostest" and diversify so fast due to a few historical contingencies that there was no "room" for large Elapids?
I didn't know that garter snakes and water snakes made venom. I two foot water snake bit me about ten times when I was summoned to get it out of our stockroom. Makes sense though. Used to feed frogs to a captive garter snake. I always wondered why the frogs gave up halfway through the fight.
So, does anyone know? Why are there no big Elapids in North America?
Sam,
1. OK, need to define what nothingness is though.
2. http://en.wikipedia.org/wiki/Anthropic
3. Check
4. Check
5. Check
6. Wishful thinking
There you go. He is almost right.
Sam, we know about Collins. Try the little search bar in the upper left of your screen.
By the way, have you met Greasemonkey McKillfile?
Bollocks. You can't speak about probabilities or improbabilities without knowing the range of possible outcomes. If you don't know how many sides a die has and how they are labeled, you can't assign an a priori probability to the outcome of rolling a 1.
Moreover, this is a shoddy way to argue for an intelligence outside the Universe. Think about it. Either that intelligence lives in an environment like ours, with the same physical laws as our Universe, or it doesn't. If the creator's environment — call it Heaven — has physical laws just like ours, then we have to explain where they came from. If it didn't, then intelligent life can exist in a Universe not like our own, and the whole argument collapses under its own weight.
Also bollocks. Collins blithely ignores inclusive fitness, reciprocal altruism and every other damn mechanism ever proposed to account for the evolution of social behaviors. (He has a habit of ignoring whole fields of human inquiry, from cosmology to history and anthropology.) Furthermore, he arrogantly conflates desires for meaning and happiness with a desire for "God", thereby presuming his own conclusion.
Collins is the prototypical example of a specialist who has experience in one subfield of science and, because he cannot abandon the idea of a personal deity, finds the fingerprints of that deity in all the sciences he doesn't understand.
Corals are related to cobras only in the sense that they are in the elapid family together. The closest relatives of the American corals are the Asian snakes in the Calliophis [Maticora] and Sinomicrurus genera, which are skinny leaf-litter dwellers. All elapids are indeed characterised by front fangs. The Texas coral is a small, in-offensive snakes. The coral snakes here in Colombia, however, are radically different. Severl species get over a meter and a couple even reach around 1.6 meters! A big elapid by any measure.
Cheers
Bryan
Bacopa,
I heard the same snakelore about coral snakes wrt fangs. Supposedly they had to chew a wound open to drool the venom into. Glad I didn't handle them.
I have seen them, they are stunning and gorgeous. But not very aggro, unlike the "non-venomous" water snakes, which were mean as a, um, snake. I mean really mean.
Somewhere recently I saw a discussion about constrictors and why their prey dies quickly. Suffocation would seem to take longer. The hypothesis was that the squeezing gets so severe, that the heart cannot pump overcome the pressure from the constrictor. So they can't breathe, and then die of no blood flow.
Re: #96
Hey, Sam-the-sham, when you post another's article (in this case, straight from Wikipedia) without attribution, making it seem to be your own words, it is called "plagiarism." You know, like how the Bible was composed.
Dr. Collins is a premier scientist, and no other scientist would disagree with that assessment. To his great credit, he doesn't let his beliefs about gods interfere with his scientific work.
Number 6 in your list is unsupported by any evidence or observation. There is no such thing as "the Moral Law," and there is no universal cultural "search for God."
Sam, your BioLogos sounds nice and theological but it's obvious the premises don't make sense.
Out of nothingness!? Where's the evidence for this nothingness?
Tell that to the people on Mars, Venus and all the other planets in the galaxy, oh wait... If you understood anything about evolution you'd know life adapts to it's surroundings.
Now you are just making stuff up while leaving us with no explanation whatsoever, "these unique features have a supernatural origin, because I say so" doesn't explain anything.
You know there are many social structures and moral codes to be found among animals btw don't you? It would make you look rather silly if you were just spouting uninformed nonsense here.
You've mentioned Sonic Hedgehog before, is there a post that describes what exactly this is and why the funny name?
Kent, let's put this in terms that even you can probably understand, based upon the semi-literate rants that you've barfed out here.
Your god is most likely to be the one called Jehova. I base that upon statistical probablity from what I surmise about you. If it isn't Jehova, but one of the other thousands of gods that people have worshipped, just replace the name Jehova with the god name of your choice.
So I challenge Jehova. Jehova, you're a feckin' asshole. You have no power. You have no abilities at all. I challenge you, Jehova, or any other god, to smite me within the next day. I do this because I know that you don't exist, so you can't harm me.
Now then Kent, you, too, can ask your feckin' god to smite me.
Kent, do you think that I won't be back on this site after tomorrow? If you do, then you're a feckin' edjit.
Kent, I wouldn't dignify your feckin' god by spelling its name correctly.
I think I remember reading somewhere that some components of mammalian semen are thought to have evolved from venom proteins; the biochemical activities involved in eating through the ovum's protective coating to allow fertilisation are analogous to those that cause toxicity in other contexts. I foresee a trip to PubMed for me.
#113: ?
Seems more likely to me to be the other way around...successful fertilization is pretty much a prerequisite for evolving venom, no?
dr. myers you are a joy - i salute and applaud you
if ever it was anything, it was this... this! (the garden of earthly delights that is 'pharyngula')that the interwebs was invented for (:
113 is the perfect excuse to spit, not swallow.
Here is a nice picture of the lead author with a king cobra from my Dutch newspaper.
Thank you, dr Fry!
As I was reading I started pondering whence the venom came in the first place, and lo! I was not the only one and the question had even been answered thoroughly before I reached the end of the comments (kudos to Sven di Milo for a valent attempt, too).
Glad I'm not the only one to wonder when they allowed Hovind internet in the cell at the first sight of "Kent". Conditioned response much?
Sam is just dumb. The earth is not fine-tuned for life; it's fine-tuned for birds. Think about it--the surface of the earth is rather two dimensional, if given to some folding and stretching here and there. However, the sky extends from the surface of the earth to near infinity (well, along a logarithmic density gradient, that is). Why would this be the case if the earth weren't fine tuned for birds? Why would there even be a sky, since most life on earth lives on or near the ground (except for those sea-creatures like manta rays and box jellyfish, but they swim in the ocean, otherwise known as the Devil's Piss, so who cares?)
I call this the birdthropic principle, and it's the most damning indictment of both evolution and Intelligent Design since Harry Belafonte put forward the theory that "we come from the mountain/living on the mountain/go back to the mountain/turn the world around."
Not to mention that, but "the earth" is constantly trying to kill everyone. Bacteria, disease, other members of the planet, etc.
Yes we have adapted to living here, tenuously, but it is no picnic.
Actually take it one step further the universe as a whole is incredibly hostile to life for the most part, there's gotta be a better solution in the multiverse somewhere.
As a shade-tree herpetologist whose main interest is in venomous, I'd like to thank PZ & Bryan for an excellent presentation(s). I learned quite a bit -- how easy it is to fall behind on the science if you don't do it full time.
And Kent, do study at least a little of the science. You don't have to believe it but it always helps to know what the opposition is doing. That way, you might not look like quite as much of an ass when you comment.
doov
Im typing from my phone (motorola) so excuse if it looks funny.
I crushed you in my first post. No one could argue with sheer logic (EVEN THAT YOU TRIED). You darwinists come with excuses and try to abolish gods creation so you dont have to follow his law. Its tragic.
A painting has a painter but darwinist says its evolved. The things you do to keep your god dawkins.
And for him insulting god, YOU will burn in hell and when u see your innocent children and wife burning in hellfire screaming your name asking you WHY you told them there was no god, then u will remember we and how i tried to help.
You're too kind, Kent.
(A little too easy to figure out, too).
Glen D
http://tinyurl.com/2kxyc7
Evolution god? You can't be serious. This shouldn't have to be said, but you seem not to understand it, so I'll put it very clearly: evolution is not a god or a religion. There are no deities in evolution. No holy writings (there are lots of good books and papers on the subject, but NONE of them is held as sacred, perfect, or inviolable). No doctrines. Evolution follows the evidence, and if the evidence contradicts parts of the theory, those parts have to be changed. If the evidence turned out to support another hypothesis, evolution would be replaced. If you seriously suggest evolution is a religion, you're delusional, outright dishonest, or more likely misled by authorities in your church.
This shouldn't have to be said either, but that myth has become all too common lately. Hitler wasn't an atheist; he was a Christian, specifically a Catholic. He believed he was doing the Lord's work, and he modeled his Final Solution on Martin Luther's ideas for how the Jews should be dealt with ("On the Jews and their Lies"), not on the theory of evolution. In fact his ideas, if anything, were a perversion of evolution.
Millions of Christians in the world accept evolution. Being religious doesn't at all mean someone's ignorant. But your two posts above sound remarkably ignorant to anyone passingly familiar with the theory of evolution. That's why you've been told to do some reading on the subject.
In case the subject comes up, I should mention that the Bible isn't evidence for special creation for the simple reason that it isn't evidence for anything in the scientific realm: its track record of scientific statements is consistently wrong, though consistent with what people understood of the world at about the time it was written. That is, of course, unless you also believe the following are true:
- The world is flat
- The sky is a solid disk, with windows that God opens to pour rain upon the world
- The stars are points of light on the disk, and can fall to the ground
- Birds have four legs
- Insects have four legs
- Bats are birds
- Rabbits chew the cud
Re: #102
"Snake in the grass"
or "Thunderf00t's bitch"
Kent,
Your disjointed ravings would be just as stupid, and the psychopathic sadism you display in your last comment just as repugnant, whatever you typed on.
Evolution god? You can't be serious. This shouldn't have to be said, but you seem not to understand it, so I'll put it very clearly: evolution is not a god or a religion. There are no deities in evolution. No holy writings (there are lots of good books and papers on the subject, but NONE of them is held as sacred, perfect, or inviolable). No doctrines. Evolution follows the evidence, and if the evidence contradicts parts of the theory, those parts have to be changed. If the evidence turned out to support another hypothesis, evolution would be replaced. If you seriously suggest evolution is a religion, you're delusional, outright dishonest, or more likely misled by authorities in your church.
This shouldn't have to be said either, but that myth has become all too common lately. Hitler wasn't an atheist; he was a Christian, specifically a Catholic. He believed he was doing the Lord's work, and he modeled his Final Solution on Martin Luther's ideas for how the Jews should be dealt with ("On the Jews and their Lies"), not on the theory of evolution. In fact his ideas, if anything, were a perversion of evolution.
Millions of Christians in the world accept evolution. Being religious doesn't at all mean someone's ignorant. But your two posts above sound remarkably ignorant to anyone passingly familiar with the theory of evolution. That's why you've been told to do some reading on the subject.
In case the subject comes up, I should mention that the Bible isn't evidence for special creation for the simple reason that it isn't evidence for anything in the scientific realm: its track record of scientific statements is consistently wrong, though consistent with what people understood of the world at about the time it was written. That is, of course, unless you also believe the following are true:
- The world is flat
- The sky is a solid disk, with windows that God opens to pour rain upon the world
- The stars are points of light on the disk, and can fall to the ground
- Birds have four legs
- Insects have four legs
- Bats are birds
- Rabbits chew the cud
Upon further reading I have to say that Kent must be a Poe.
Also I want to bear dr Fry's children. And I hate children. And I don't have ovaries ...
By the way, who does the PR for "Giant Squid"? I mean, they're big, yes, but "giant"?
I think in protest, I'll have to start referring to them as "Big Squid" - and 'Colossal' Squid can then be "Really Big Squid".
Interesting to see how clever dr Fry was in immediately bringing up cephalopodes, thus securing himself the blessings of the Power That Be.
Evolution god? You can't be serious. This shouldn't have to be said, but you seem not to understand it, so I'll put it very clearly: evolution is not a god or a religion. There are no deities in evolution. No holy writings (there are lots of good books and papers on the subject, but NONE of them is held as sacred, perfect, or inviolable). No doctrines. Evolution follows the evidence, and if the evidence contradicts parts of the theory, those parts have to be changed. If the evidence turned out to support another hypothesis, evolution would be replaced. If you seriously suggest evolution is a religion, you're delusional, outright dishonest, or more likely, misled by authorities in your church.
This shouldn't have to be said either, but that myth has become all too common lately. Hitler wasn't an atheist; he was a Christian, specifically a Catholic. He believed he was doing the Lord's work, and he modeled his Final Solution on Martin Luther's ideas for how the Jews should be dealt with ("On the Jews and their Lies"), not on the theory of evolution. In fact his ideas, if anything, were a perversion of evolution.
Millions of Christians in the world accept evolution. Being religious doesn't at all mean someone's ignorant. But your two posts above sound remarkably ignorant to anyone passingly familiar with the theory of evolution. That's why you've been told to do some reading on the subject.
In case the subject comes up, I should mention that the Bible isn't evidence for special creation for the simple reason that it isn't evidence for anything in the scientific realm: its track record of scientific statements is consistently wrong, though consistent with what people understood of the world at about the time it was written. That is, of course, unless you also believe the following are true:
- The world is flat
- The sky is a solid disk, with windows that God opens to pour rain upon the world
- The stars are points of light on the disk, and can fall to the ground
- Birds have four legs
- Insects have four legs
- Bats are birds
- Rabbits chew the cud
Re: #123
Please keep posting, Kent! Nothing makes our case like an honest creationist such as yourself.
If you really wanted to help, you would have posited cogent arguments rather than baseless insults. Clearly, you don't give a fig about helping us, but rather adding another 'witness' notch to your belt so you can claim you were doing God's work when you croak.
But He'll see through your pompous primping and preening, and send you right where you belong, you fucking Pharisee wannabe.
If people like you have a soul, it must be the ugliest thing in all creation, you repugnant, selfish little thug.
Kent,
Use some BOLD and Italics and try to randomly capitalize more. Maybe throw a few extra disjointed random thoughts in there. Other than that you're doing a bang up job.
I'm just trying to help.
Don't feed Kent. He is bughouse crazy. Prison hasn't been a good experience for him. One of the basic tests we do is "orientation to person, place, and time." He flunked the time one and will probably flunk the other two. It is 2008 and the Soviet Union disappeared over a decade ago.
A simple test and you would be surprised how many people can't answer all three questions.
Well Kent...
"The first fully automatic mobile phone system, called MTA (Mobile Telephone system A), was developed by Ericsson and commercially released in Sweden in 1956. This was the first system that didn't require any kind of manual control, but had the disadvantage of a phone weight of 40 kg (90 lb). MTB, an upgraded version with transistors, weighing 9 kg (20 lb), was introduced in 1965 and used DTMF signaling. It had 150 customers in the beginning and 600 when it shut down in 1983."
Greetings from godless sweden!
Sven, #114:
You may well be right (a brief PubMed scan brought up mentions of common ancestry but not of the direction of derivation). But it might also depend on the kind of ovum and the barriers a sperm cell needs to come in order to fertilise it. I'd imagine that these might be different in species where fertilisation occurs via the release of both sperm and ova into water, than in mammals.
Can you tell I'm not an expert?!
I meant, of course, to say "needs to OVERcome". I can't think where that Freudian slip could possibly have come from.
BigDumbChimp, I think he's doing fine all by himself, no suggestions are necessary or will be in the near future.
Random capitalization - check
Disjointed thoughts - check
Godwin's Law - check
Feelings of grandeur - check
Suspension of reality - check
Did I forget any?
Doug #138
Your forgot the bad odor left in the thread. Skunks are nice compared to trolls.
I'm going out on a limb here but..
Mouth Breathing - Check
Frothing and spittle on monitor - Check
@129: Yeah, I've been think Poe for a little while now. Hard to tell real crazy from fake crazy sometimes though.
"Kent, congratulations you manged to be wrong in every sentence. That has to be some sort of record."
Posted by: Natasha Yar-Routh | July 31, 2008 12:00 PM
actually, it's pretty much par for the course. i would have been surprised if he had NOT been wrong in every sentence.
Ha Ha Ha.
How bout'
Uncontrolled Masturbation - check
Doug Little: Actually take it one step further the universe as a whole is incredibly hostile to life for the most part, there's gotta be a better solution in the multiverse somewhere.
Read Greg Egan's Schild's Ladder. Or for a non-fiction version, read some of Max Tegmark's papers on self-aware mathematical constructs.
Until someone is capable of showing what the set of self-consistent universes is, we have no idea what the best of all possible worlds could possible be.
"cars? airplanes?"
Apparently they're still riding horses and trading livestock in Europe and the USSR.
"Ken" couldn't be real, I think he's just a comic foil to all the enlightening discussion on this thread. A paper shows an interesting facet of the evolution of the snake, one of the most feared animals in the human psyche, and one of the authors shows up to share his insights and the fresh tropical air that he gets to breathe. How much more fulfilling that is than the tiny mind who can't see past the petty tribal myths of long-ago peoples?
"They just want the world to be as simple as they are." -Tim Krider
Thank You Dr. Fry for letting me know that coral snakes might have more fang than I have been led to believe. I will never pick one up should I be lucky enough to find another one. And thanks also for the info about larger corals in South America. But why are there no large Elapids in North America? We have huge vipers here. I got put off snakewatching for a while when I encountered an eastern diamondback near the Trinity Bay lobe of Galveston bay. I was trying to collect brackish water Poecilia and create a strain of saltwater mollies as feeder fish and make some bucks. I broke even until the cat turned off the powerstrip and all my fish died.
So why aren't there any big Elapids in North America? I can only think that some historical accident allowed the vipers to take over all the badass venomous snake niches.
I agree with the previous commenter that water snakes are mean as hell. Maybe that's why there are so many of them. They must breed like crazy because I've seen a heron eat five of them in ten minutes at the retention pond near work and there are still plenty more.
I live in the part of the US the Burmese python could go feral in. I tried to Google whether these snakes were still legal in Texas, but couldn't find a decisive answer. TX is usually pretty good about banning potential invasive species. I'd hate to see our local gators which have only just again become comonplace threatened by a giant snake.
On second thought, maybe I really meant "tragic foil".
Kent, "...YOU will burn in hell and when u see your innocent children and wife burning in hellfire screaming your name asking you WHY you told them there was no god,..."
Well, you say your god will punish the innocent for its vengeance on others. What a fecker! That's you & your feckin' god.
Nah, you must be a 'Poe' - no one could be that stupid.
"PZ has been one upped! :O"
http://www.catholicleague.org/release.php?id=1468
""Catholic schoolboy traditions are fair game for a play that pokes gentle fun at Catholicism. But that is not what this play is about: There is nothing gentle about mocking the Eucharist. This should be known even to those who are not Catholic."
Oh, Billy boy*. Don't you see the can of worms you've opened up? Now nobody can take the Eucharist seriously anymore. Hell, even the lapsed Catholic writing this had a little respect for it until this whole episode. Now I have less than none.
* Possible Irish slur? No wait, we've established that William is a proddie name.
"This play would be objectionable if it were paid for with private donations, but when it is funded by the taxpayers--most of whom are Catholic in Rhode Island--it is a total rip off. And it again demonstrates that the so-called church and state issue cuts just one way: while it is illegal for public institutions to promote Catholicism, they apparently can bash Catholicism with impunity.""
Sounds like a fine deal to me. Come on, Billy, you don't need The State*. You got lots of other friends who like you just the way you are!
* When the god-damned holy hell are they gonna release that State DVD anyway?!
Kent just HAS to be a Poe. No one on the face of the planet can be that irredeemably stupid, can they? Oh, dear, I have just been informed that they can.
Has anyone actually looked at Dr. Fry's pics? OMG, he's a hottie! Would that I were 20 years younger.......
Seriously, I never thought I would find snakes and their venom delivery systems to be so fascinating. Thanks ever so, PZ and Brian, for presenting a complex subject in a way that this humble layperson can understand without my eyes glazing over.
I will think of you when I'm checking out the stripper factory and beer volcano.
Of course, Kent is a Poe. He seems to be doing a good job of it too, judging by the responses (then again, those who respond to any given parody are hardly a random sample of those who read it).
My initial (and thus far unchanged) conclusion was that the name was a nod toward the inspiration for his parody.
thanks all for an educational and entertaining post and thread.
and can i make a request for more pictures of dr. fry more often?
His first post on this thread, #24, was believable.
The others have not been.
Glen D
http://tinyurl.com/2kxyc7
OT, but I'm gonna have to check that out. I've never read any of Egan's novels, but he's been my favourite SF short story and novella authors ever since I discovered him in one of Gardner Dozois's The Year's Best Science Fiction a decade or so ago. Thanks, frog.
Bryan Fry@46, bravo! Just when I was thinking that it was a pity that PZ's science posts got so very few responses, something like *this* pops up. Fascinating. I'd heard vaguely of the mechanisms of toxin evolution, but never as clearly as this. (Plus, of course, there's the whole from-the-snake's-fangs[1] thing: those who studied it can often explain it better than anyone else.)
[1] more appropriate than horses' mouths here, I feel
Brownian: Read Diaspora. That's his best!
Will do, frog. Thanks again!
Thanks, PZ. I look forward to reading this all again later, when I can give it my full attention and really absorb all of the information.
And Bryan Grieg Fry - What can I say? Add another Pharyngucrush to the list. However,
Well, I just love how after people bust their butts commenting here all month defending reason from dogma, some dude slithers in on the 31st with his biting remarks and gets himself nominated for a Molly. :)
MH:
Yeah. [/Trading Places sidekick voice]
Posted by Sven DiMilo @ #11:
"The evolution of venom preceded the evolution of fangs. Venom probably started with the expression of intestinal digestive-enzyme genes in saliva...That sets up selection pressures for improved (nastier) venom and a more efficient delivery system (fangs)."
I was going to comment that it has been discovered that monitor lizards such as the komodo dragon possess venomous saliva, but I notice that Bryan Fry has already mentioned it in post #61. 'Sacre bleu', people respond quickly around here.
I am curious however, about how the levels of toxicity in the saliva of other monitor lizards such as the Australian goanna, compare to those of the komodo dragon.
I can recall having seen cattle dogs experiencing nasty localised inflamatory reactions after being bitten by goannas, but I'm not sure whether the toxins were likely to have also produced any kind of systemic reaction. The dogs appeared to be somewhat lethargic after being bitten, but I always assumed that they were just taking it easy because of their injuries.
#149:
When the god-damned holy hell are they gonna release that State DVD anyway?!
Wow, a The State reference on Pharyngula! :-D I don't know, but they have clips up on MTV's website. Though, you have to sit through ads, unfortunately. :-/
I will definitely be buying it whenever it does come out!
Leon - you mention "bats are birds" as one of the sillinesses found in the Bible. I'll play the Devil's advocate here and suggest that this be dropped. The bible didn't say this; English translations of the bible did. The Aramaic(?)word translated into "birds" probably meant something like "flying beast, not bugs". It is not a biological category to be sure, but is a perfectly logical one, especially for bronze-age goatherds. Think of it as akin to "pachyderm" or "bug" (as most people use it).
And pi does equal three, for anyone whose math is limited to counting on their fingers...
>I am curious however, about how the levels of toxicity in the saliva of other monitor lizards such as the Australian goanna, compare to those of the komodo dragon.
writing up that paper literally at the moment (on 12 Aussie goannas).
Cheers mate
B
Just like my mama always told me.
I echo Jeff's recommendation of Neil Shubin's 'Your Inner Fish' for those of you wanting to learn more about Shh. It's a fantastic read for people at all levels of scientific literacy. Pick it up!
As for why the gene got such a funny name... I assume it's just because the scientists who discovered the gene had free reign to name it whatever they wanted, and thought it was a cool name. I myself am still dreaming about being able to name a gene. That would be the best.
>I am curious however, about how the levels of toxicity in the saliva of other monitor lizards such as the Australian goanna, compare to those of the komodo dragon.
writing up that paper literally at the moment (on 12 Aussie goannas).
Cheers mate
B
Wow, reading Kent's posts is a wonderful nostalgia trip, a return to the run-of-the-mill fundie cretard trolls, rather than the rabid "Bill Donohue sent me" trolls.
Thanks for dropping science again, professor!
Mike way up there - it's pretty rich that the Catholic League criticizes a play it doesn't like for being publicly funded. The Catholic Church continually tries to get its hand into the public purse. Taxpayer-supplied books, meals, etc. - on the grounds that the kids will suffer unless their "superior" Catholic education isn't funded by the public. If Catholic schools are so good, why aren't parents willing to pay the freight, like other users of private schools?
PZ -Thanks a lot for the wonderful science post! Keep 'em coming.
Bacopa: It might be to do with the fact that viperids seem to do okay with temperate climates, whereas elapids appear to be nearly exclusively tropical or subtropical species. My guess is that it could be climatic factors which prevented elapids from crossing the Bering Straits*; viperids might have easily crossed over during a warmer period that was still too cold for the elapids. A cursory browsing of the Wikipedia pages on these two families reveal that quite a number of species of viperids are found in temperate East Asia, so they should be pretty cold-tolerant**.
*That is, if these snakes got across via the north Pacific, and not via the Atlantic.
**But I cannot fathom why the Old World Vipera, which actually ranges into the Arctic Circle in Europe, never made it to North America.
I have no idea how the snakes diversified and spread around the world in the Cenozoic, but it appears that only one lineage of elapids ever made it to the Americas, giving rise to the coral snakes. Similarly, you might be aware that all American viperids belong to a single lineage, the crotalines or pit-vipers. Both elapids and viperids are much more diverse in Africa and Asia, and my take is that both groups evolved somewhere in the Old World, before subsequently spreading around the rest of the world. No idea how they managed to diversify so much without coming into direct competition, but representatives from both families can be found sharing the same habitats in most of Africa and Asia.
Australia and surrounding islands in the Pacific are apparently where elapids are at their most diverse*, and maybe it's no coincidence that viperids are completely absent (the closest viperids are in Indonesia and the Philippines). I'm not sure if the Australasian elapids form a monophyletic grouping within the family, to the exclusion of their African, Asian, and American relatives. Or if they are the most basal, or the most derived elapids.
*Not counting the sea snakes.
Similarly, the pit-vipers might have made it to the Americas first, and then quickly spread and diversified into various niches. By the time the coral snakes made it across, they possible entered a world already dominated by pit-vipers, so they could not diversify as much.
Australia --> Viperids absent; Elapids highly diverse
Americas --> Limited diversity in elapids; Viperids (crotalines) highly diverse
In any case, though both elapids and viperids are highly successful and highly diverse families that have colonised much of the world, it is interesting to note that both families are at their most diverse (in terms of number of species and diversity of forms and niches), in the continents where the other family is either absent or not as diverse.
It would be extremely interesting to see how the evolution of both these families has played out over the course of the Cenozoic, and factoring in possible competition with all the other widespread and diverse snake families, such as the natricids, colubrids, pythonids, and boids. Damn, the idea of a squamate supertree is making me drool with excitement...
I think I've fallen in love. Yay, Dr Fry! Curiously, the other bloke that I'm in love with at a distance is also a Fry - Stephen. Big fan.
Greg Egan: yes! All good. Best hard SF in decades.
Sonic hedgehog comes from a drosphila lab tradition, where genes were named after the problems that their malfunction caused. Hedgehog made the flies go all spiky. The tradition is now causing some problems and there are moves towards renaming. It's sad, but now that we know more about genetics, we know the human equivalents, we know the diseases. The names stop being funny when applied to a real live suffering human.
Other funny gene names include: groucho, smurf, headcase, cheap date, tinman, lunatic fringe, half stoned, mothers against decapentaplegia...
I've really enjoyed PZ's post and most of the comments (especially Dr. Fry's), but I do have a small nit-pick for PZ who wrote: "Then there are the Viperidae, rattlesnakes and pit vipers and copperheads.." Actually, both rattlesnakes and copperheads belong to the viper sub-family, Crotalinae, which comprises the pit vipers.
Pit vipers are distinguished by a deep pit under each eye. These orifices are highly sensitive to heat produced by warm-blooded animals. Since the pits are arranged on each side of the snake's face, they provide a kind of stereoscopic heat sensing system, which not only can detect the direction of the heat sorce, but its size and its distance from the snake. This gives pit vipers the advantage of entering the burrows of small rodents and finding and killing them in complete darkness.
So, "Then there are the Viperidae, including pit vipers such as rattlesnakes and copperheads.."
Fixed.
Just a quick thank you to the landlord, along with Bryan Grieg Fry, Hai~Ren, and other commenters for a fascinating discussion.
Bryan Fry wrote @ #163:
"writing up that paper literally at the moment (on 12 Aussie goannas).
Cheers mate"
You beauty! Where is it likely to be published?
Perhaps PZ might consider doing a follow up post on your results?
By the way, do you ever run into Peter Harlow, the reptile and amphibian manager at Taronga Zoo in Sydney?
I worked with Peter for a couple of years at the University of New South wales many moons ago, where I remember him regaling us with tales about wading up to his neck in crocodile infested billabongs in the Northern Territory, collecting file snakes. And collecting wild saltwater crocodile eggs, while Professor Grahame Webb stood guard brandishing a wooden boat paddle, with a colt 45 pistol strapped by his side, just in case mama-croc decided to turn up unexpectedly and object to their nefarious activities.
One day Peter even managed to talk ME into splashing around with him in the alligator enclosure at Taronga Zoo, in an attempt to net some small fish to feed to some juvenile crocs which we were keeping back at the University campus at the time. That's the first and last time I ever want to do that. Peter however, thought it was great fun.
You herpetologists really are a strange mob aren't you? : D
kermit:
leon wrote:
I just felt that needed to be pointed out.
Oops, I meant to add:
The point is not that the bible is wrong or why those errors were made.
The point is that people who insist that it is 100% true (then, now and forever), are idiots.
This really is a great thread: thanks to PZ and Dr Fry for presenting fine, accessible science.
And thanks to Kent for providing the fundamental sillyness. Tho' I'm pretty sure he's a Poe, he's certainly much more entertaining than them there Cafflicks.
OK, carry on...as you were...
Andy
Molly, hell! Can Seed/Sb recruit this guy?
My goodness, this thread is fun.
Hai-Ren #170, the Australasian terrestrial elapids (including both, independent, lineages of sea-snakes) appear from DNA studies to be the sister group of all-other-elapids (i.e. African forms, with several excursions to Asia resulting in kraits, king cobra, and the coral-snake lineage that managed to cross Beringia once). That makes it uncertain where the first elapids lived, because apparently no extant forms are outside the split between those Australia-based and Africa-based radiations. The oldest fossils so far are here in Australia, but there's no way that elapids are old enough to be Gondwanan. Resolution of relationships with other colubroid groups suggests an ultimate African origin, implying the inital elapid radiation (in Africa, extending to Australia probably via Asia) ultimately went extinct except for one African and one Australian species, ancestral to the two modern groups.
The Vonk et al. paper is very cool, but not at all surprising - development of the colubrid maxilla in two parts was described decades ago, with suggestions it had some evolutionary connection with the Bolyeriid snakes (Casarea, Bolyeria) in which the maxilla actually has a joint between separately ossified front and back halves in adults. And it seems very clear that elapids and vipers lack the front end of the maxilla; in contrast to colubrids there is a big notch in the upper jaw skeleton between maxilla and premaxilla. But actually demonstrating the developmental mechanisms behind the diversity of the modern adult forms is something else; in this case it finds no difference between elapids and vipers, but it might have found something else instead.
And Hi Bryan, I've seen a couple of pretty red adders in front yards in town lately. Haven't heard from you in a while, but clearly you've been busy!
John Marley@175,
People thought insects had four legs back then?
Quid est Sonic Hedgehog?
At least what is it in this context? And how did it get that name? I know about the nintendo game.
Posted by: Lynnai | July 31, 2008 11:04 AM
Oooh me me! A science question I know the answer to!
(apologies if it has been answered already - these threads are far too long!)
Well you see, in the early days, scientists did the majority of their developmental genetics work on fruit flys, and it involved a lot of knocking genes out and seeing what happened.
One such knock-out experiment produced a fly with defects in the spiky hairs growing on its body, so they called the gene responsible 'hedgehog (hh)' due to the hedgehog-like appearance of the fly.
Later on, as more work was being done on other model organisms, such as mice, fish and chickens, they started to find homologues of many of the genes discovered in the fruit fly. This wasn't entirely expected, but it was a major chunk of supportive evidence to that evolution theory.
Anyway, a number of hh homologues were found, and so they were given hedgehogy names, such as the lesser known 'Indian' and 'Echidna' hedgehogs. It was around this time that Saga brought out their little blue spiky friend, and as those crazy scientists are such droll characters, the latest hh gene/protein was thus christened.
Incidently, how cool would it be to work on snakes?! Where is this lab? GFP fish are sooo 2005. GFP snakes would be interesting, yet also practical - you would be able to spot an escapee a mile off - no more getting bitten whilst on the dunny (well at least if you have a uv light)
Sega...
Gotta love it!
"All share a common ancestor that had venom glands but used ordinary teeth to chew the venom in."
Venom glands from some digestive gland precursor(s)?
Look at it this way, Kent. God created a life-generating universe a bit like a trial and error self-erecting and self-improving improving leggo set. One where he could rest after creating it and know that it was good. Still a metaphor, but a clearer metaphor than one that worked for yokels in the middle east a few thousand years ago before it got garbled and literalized.
Hi all,
How nice to see so much discussion here after a [splendid] review of our paper by Prof. Myers. Great stuff. I read it with great interest.
Quote John Scanlon: "The Vonk et al. paper is very cool, but not at all surprising - development of the colubrid maxilla in two parts was described decades ago, with suggestions it had some evolutionary connection with the Bolyeriid snakes (Casarea, Bolyeria) in which the maxilla actually has a joint between separately ossified front and back halves in adults."
Hi John,
Thanks for your comments. There is a difference however between the two ossification centers of the maxilla bone that Haluska and Alberch showed in Elaphe obsoleta (in 1983), and the two tooth-forming layers that we show. These might not even be correlated, we don't know (yet). A good analyses of the tooth-forming tissue and the maxilla development in the same specimen could shed more light upon this.
Btw, we looked at Casarea teeth through scanning microscopy, and could not find any morphological difference between the teeth on each of the two maxilla halves.
Best wishes,
Freek
www.evolutionbites.com
That's a good point. I wouldn't know anything about the original versions, as I've only read the KJV. Perhaps I should leave the bats alone in the future.