Pharyngula

A dolphin…with hindlimbs

Now this is cool:

i-fa3e93329362492341873077f5bcdc28-4fin_dolphin.jpg

Just as sometimes humans are born with little tails, it seems that a few bottlenosed dolphins are born with vestiges of hindlimbs. The genetic toolbox for making limbs is all there, and sometimes it can get re-expressed, revealing these fascinating atavisms.

Comments

  1. #1 Ichthyic
    November 6, 2006

    While fascinating for providing more evidence of the mechanism of evolution, I suspect that it is actually evidence of a species under stress.

    Studies I was involved with a long time ago (about 20 years ago)on organophosphate contamination in Pacific Bottlenose Dolphins revealed very high levels (higher than for any previously recorded tissues from any mammal) for PCB’s and DDT metabolites (DDE).

    I’ve periodically checked over the last 20 years, and the situation does not seem to be improving much; many marine mammals are exhibiting signs of physiological stress that may be from high levels of organochlorine/phosphate residues. likely high levels of mercury too, but I never looked at those. preliminary work I was helping with about 10 years ago around Monterey Bay, CA, with elasmobranchs also revealed high levels of similar contaminants.

    However, I have no idea as to the likelihood of these kinds of toxics affecting expression of these particular traits.

    A lot more data would be needed, and apparently the condition is rare enough (in delphinids) that it would be difficult.

    I wonder if comparative tests for the effects of these kinds of contaminants in the development of other species that have dropped limbs might shed some light? That would be more PZ’s forte, I would think, and maybe he has some relevant references to share?

    IIRC in snakes, a Hox gene complex is involved in the expression of this trait. I don’t know if it is the same in delphinids, but maybe it would shed light on the situation if we did some developmental studies on snakes using similar concentrations of organochlorine/phosphate residues?

    just a thought.

  2. #2 Ichthyic
    November 6, 2006

    Come on people, let’s get real and quit sightlessly grasping for evidence. Find us something UNDINIABLE[sic] if that’s what evolution is.

    uh, joe, not that you would have anything intelligent to respond with, and not that this particular data point is anything but a curiosity raiser to see if delphinids share similar developmental pathways to other legless wonders, like snakes, but your post begs the question:

    what would you consider “undiniable” evidence?

    (guess: you’re gonna say something stupid, like a dog giving birth to a cat, right?)

  3. #3 Joe
    November 6, 2006

    Oops, made a mistake and that I’ll admit to it, my bad Mr. Let’s Poke Fun at People Magnus. You know that’s one of the main reasons I’m turned off with evolution. I’ve never had or seen a conversation with an evolutionist that doesn’t involve condescending remarks against the opposing side. Would one of you out there please prove to me that your not all a bunch of evolution “Pharisees” walking around in your robes of science (in by which the threads are constantly changing).
    And Ichthyic, show me some transitional fossils. If creatures evolved over millions of years, we should be literally tripping over thousands, perhaps millions of transitional forms. Yet here we are with a handful of possible maybes that are consistently disproved by secular scientists. Where are the thousands of fossils, Find me a couble hundred and I’ll start consider that undeniable.

    “I fully agree with your comments on the lack of direct illustration of evolutionary transitions in my book. If I knew of any, fossil or living, I would certainly have included them. You suggest that an artist should be used to visualise such transformations, but where would he get the information from? I could not, honestly, provide it, and if I were to leave it to artistic license, would that not mislead the reader?”
    -Dr. Colin Patterson, senior paleontologist at the British Museum of Natural History, in letter to Luther Sunderland, April 10, 1979. Cited in: Sunderland, Luther D., Darwin’s Enigma: Fossils and Other Problems (El Cajon, CA: Master Books, 1988), p. 89.

  4. #4 Magnus
    November 6, 2006

    Actually you asked Ichthyic that question, but since i’m such a nice, godless, evolutionary layman I’ll give you some references that I doubt will be accepted.

    http://www.talkorigins.org/faqs/faq-transitional.html

    Notice to self: Must stop feeding the trolls.

  5. #5 Ichthyic
    November 6, 2006

    This just seems like a Hox gene mutation expressing fins in the wrong location. Not much more.

    not much more?

    what the hell more would you want at that point, considering than in all analogous situations, it’s a hox gene complex that regulates development of limbs?

    I suggest you take a gander at the relevant sections on evolution and hox gene regulation (especially wrt limbless wonders like snakes), in a text like Scott Gilbert’s Developmental Biology

    or, just google for recent articles on the developmental basis for limb reduction.

    frankly, I think you haven’t a clue what that would mean, if it really is tied directly to a hox gene system.

  6. #6 Ichthyic
    November 6, 2006

    Don’t blame the bible for people’s misinterpretations.

    don’t blame people for the bible’s misinterpretations, either, right?

    or should we just blame you?

    the translators?

    King James?

  7. #7 Ichthyic
    November 6, 2006

    I guess I have always thought that hox genes act as master switches. They determine where, during embryonic development limbs are expressed. Tinkering with these genes can cause an extra pair of wings on a fly to develope or an antenna to develope where an eye should be. Or a cow or cat
    developing an extra pair of legs. I have seen this phenomenon quite a few times. It is not uncommon. I’m just suggesting that there was this same sort of mutation in this dolphin causing fins (front fins, miniscule, malformed and underdeveloped) to be expressed in the wrong place. The same information duplicated for front fins.

    Nothing new.

    the question is, in looking at other vertebrates we see homologous hox systems controlling limb development. Hence your “nothing new” statement glosses over the most important part, the fact that there are conserved systems regulating this trait that are common to many vertebrates.

    are you really telling me you don’t see the implications of that?

    again, it does appear you are perhaps missing the whole point, to put it mildly.

    It’s like saying there is nothing significant in the pattern of breakage in the vitamin C gene in primates.

    “well, chimps and humans both have a broken vitamin C psuedogene, so what’s new?”

    does that make it somewhat clearer for you?

  8. #8 Ichthyic
    November 6, 2006

    … we can learn from abberations like this specific example, whether or not homologous patterns in development are seen here as in other vertebrates.

    so, yeah, considering we can’t normally run experiements with mutagens on dolphins to see the effects on development, even single data points like this are valuable in teasing out relationships.

    it doesn’t matter if it’s a mutation (of course it is, duh), it’s how the mutation affected development that is of interest.

    we learn tons about development by “breaking stuff”, or didn’t you catch the alcohol effects on development thread PZ posted a couple weeks back?

    or, hell, read Gilbert’s devo text.

  9. #9 Ichthyic
    November 6, 2006

    as to:

    I know Basilosaurus had hind limbs, but I doubt they were vestigial. Even a Charlie worshipping bible like National Geographic states they most likely served a function for mating. It’s not just creationists saying that.

    you might want to gander at this article:

    http://www.blackwell-synergy.com/doi/abs/10.1111/j.1525-142X.2004.04008.x?cookieSet=1&journalCode=ede

    besides, even taking your argument at face value, have you ever heard of a thing called co-option?

    why would you conclude vestigial limbs couldn’t be used as mating aids as well?

    the two are not mutually exclusive.

  10. #10 Joe
    November 7, 2006

    JackGoff
    “Your God is obviously a sadistic being. I mean, he knows what he was doing, right?”
    Of course God knows what He is doing, but do you. Don’t base God’s identity off of mans selfishness and stupidity. We were made in His image, unfortunately, the qualities that make Him God we chose to shed. Although I’m sure some believe they are gods. And before someone throws a hissy, I’m not implying any of you.
    And along these same lines Ichthyic, yes blame me, blame me all you want, but don’t blame my God. And quit assuming I’m some king of King James only fanatic. I read many different translations but when I study I go to the Hebrew and Greek. That’s what scientists do, when something is misinterpreted and the formula’s not quite working out, you go back to the very basic structure that’s be proven over and over to work and start from there. Now whether or not the scientist chooses to use the science for good or evil is up to him, it does not the reflect the science itself. A bit philosophical but you get what I mean. Men have used the name of God to do many horrifying things no doubt. This does not mean God is horrible. I’m not trying to convince you of His existence here, but I am giving you my point of view. That is what blogs are for right.
    Look I have know reserves in saying that I’m sure you all are intelligent, educated, and moral people, but when someone voices an apposing view, act like it. Name me one situation where throwing insults at someone has resolved an issue. Good grief just turn on the TV it’s enough to drive you nuts with all the political adds throwing insults at one another.
    You have to drowned all of that out and vote for the issues because the people running obviously have more negative material on the opposed than positive on themselves.
    This being my last post I will speak my mind on the issue the best I can. Evolution vs. creation will never cease to exist. As long as people have hope in something more than being the result of a random chance and as long as we continue to walk through the greatest museums in the world with no more proof to evolution than illustrations of missing links drafted from fragments of skeletal remains, (and don’t say that’s false, I’ve been in museums all around the world, I’ve seen them) this will remain a debate, and sadly for PZ and his subjects, will be pushed into the classroom.
    I believe it was you yourself who said “If you don’t care enough for the truth to fight for it, then get out of the way.”, so PZ the fight continues.

  11. #11 Ichthyic
    November 8, 2006

    This being my last post

    anybody taking bets on that?

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