Organisms
pharyngula | May 9, 2006
Diploblasts are popping up everywhere this week. If you take a look at the phylogeny in this article, you'll see that one of the diagnostic features of the cnidarians is the presence of the cnidoblast, which contains a stinging nematocyst. This is the 'stinger' of the jellyfish…and now it's been caught on video. It's very cool—watch the movie!
pharyngula | May 8, 2006
The Wnt genes produce signalling proteins that play important roles in early development, regulating cell proliferation, differentiation and migration. It's hugely important, used in everything from early axis specification in the embryo to fine-tuning axon pathfinding in the nervous system. The way they work is that the Wnt proteins are secreted by cells, and they then bind to receptors on other cells (one receptor is named Frizzled, and others are LRP-5 and 6), which then, by a chain of cytoplasmic signalling events, removes β-catenin from a degradation pathway and promotes its import into…
pharyngula | May 8, 2006
One of the hallmark characters of animals is the presence of a specific cluster of genes that are responsible for staking out the spatial domains of the body plan along the longitudinal axis. These are the Hox genes; they are recognizable by virtue of the presence of a 60 amino acid long DNA binding region called the homeodomain, by similarities in sequence, by their role as regulatory genes expressed early in development, by the restriction of their expression to bands of tissue, by their clustering in the genome to a single location, and by the remarkable collinearity of their organization…
pharyngula | May 8, 2006
There are quite a few genes that are known to be highly conserved in both sequence and function in animals. Among these are the various Hox genes, which are expressed in an ordered pattern along the length of the organism and which define positional information along the anterior-posterior axis; and another is decapentaplegic (dpp) which is one of several conserved genes that define the dorsal-ventral axis. Together, these sets of genes establish the front-back and top-bottom axes of the animal, which in turn establishes bilaterality—this specifically laid out three-dimensional organization…
pharyngula | May 8, 2006The Cambrian vendobiont S. psygmoglena, gen.sp.nov., composite photo of part and counterpart to show both upper and lower surfaces.
From the pre-Cambrian and early Cambrian, we have a collection of enigmatic fossils: the small shellies appear to be bits and pieces of partially shelled animals; there are trace fossils, the tracks of small, soft-bodied wormlike animals; and there are the very peculiar Edicaran vendobionts, which look like fronds and fans and pleated or quilted sheets. In the Cambrian, of course, we find somewhat more familiar creatures—sure, they're weird and different, but we…
pharyngula | May 5, 2006Octopus maya
¡Viva el Cinco de Mayo!
Figure from Cephalopods: A World Guide (amzn/b&n/abe/pwll), by Mark Norman.
pharyngula | May 1, 2006Hey, I'm back home again, and crawling through my mail. While I'm simultaneously trying to recover from a long, long drive, skim through a mountain of mail, and get caught up on essential grading (there are days I'm glad I have three brains), read Circus of the Spineless #8. I will be back in the blogging business sometime soon.
pharyngula | April 28, 2006This week's Friday Cephalopod is reader submitted.
Sepioteuthis lessoniana
And there's more at Andre Seale's gallery!
pharyngula | April 27, 2006The Squid blog links to a wonderful National Geographic video of the Humboldt squid. Watch them attack divers! I cheered! Alas, the squid's efforts to taste monkey meat were frustrated, and the noble beasts have not learned to love the taste of sweet manflesh…yet.
pharyngula | April 27, 2006This strange fish is Euphanerops longaevus, which is one of two species of 370 million year old jawless fishes (the other is Endeiolepis aneri, and the paper suggests that they may actually represent differently preserved members of the same species). These are soft-bodied animals that are usually poorly preserved, and are of interest because they seem to have some properties in common with both the lampreys and the gnathostomes, or jawed fishes. Their exact position in the vertebrate family tree is problematic, and the experts go back and forth on it; sometimes they are grouped with the…
pharyngula | April 22, 2006
Hey! Coturnix is horning in on my turf, with a link to fornicating devil beetles (these are not popular beasties in my neighborhood—we get swarms of them every summer, crawling through every crevice to invade our house.)
It's cool to see, but I may have to send a few of the boys over to the quail-man's house to teach him a lesson. Either that or reconcile myself to the fact that my niche faces growing competition.
pharyngula | April 21, 2006a–c, The wing spots on male flies of the Drosophila genus. Drosophila tristis (a) and D. elegans (b) have wing spots that have arisen during convergent evolution. Drosophila gunungcola (c) instead evolved from a spotted ancestor. d, Males wave their wings to display the spots during elaborate courtship dances.
It's all about style. When you're out and about looking for mates, what tends to draw the eye first are general signals—health and vigor, symmetry, absence of blemishes or injuries, that sort of thing—but then we also look for that special something, that je ne sais quoi, that dash of…
pharyngula | April 21, 2006Sepioloidea lineolata
Figure from Cephalopods: A World Guide (amzn/b&n/abe/pwll), by Mark Norman.
pharyngula | April 20, 2006We had some rain overnight, and this morning the sidewalk on my way to work was swarming with earthworms and slugs. The slugs here in Minnesota are tiny little pathetic things, unlike the lovely behemoths I grew up with in Washington state, but they're still cool to see. Anyway, Afarensis led me to this short photoessay about what happens when a hungry slug meets a worm. I am not surprised at all: I've seen a few cannibalistic slug feeding frenzies in my time. They're like the slo-mo sharks of the damp undergrowth.
pharyngula | April 19, 2006My pedipalps were slavering at the news of a symposium on spider sex to be held on the Catalan coast of Spain. Ah, if only I had a legitimate excuse (other than prurience) and a budget that could handle the expense…
pharyngula | April 19, 2006It's a busy time for transitional fossil news—first they find a fishapod, and now we've got a Cretaceous snake with legs and a pelvis. One's in the process of gaining legs, the other is in the early stages of losing them.
Najash rionegrina was discovered in a terrestrial fossil deposit in Argentina, which is important in the ongoing debate about whether snakes evolved from marine or terrestrial ancestors. The specimen isn't entirely complete (but enough material is present to unambiguously identify it as a snake), consisting of a partial skull and a section of trunk. It has a sacrum! It has a…
pharyngula | April 18, 2006The relative length of bat forelimb digits has not changed in 50
million years. (a) Icaronycteris index, which is a 50-million-year-old bat fossil. (b) Extant adult
bat skeleton. The metacarpals (red arrows) of the first fossil bats are already
elongated and closely resemble modern bats. This observation is confirmed by
morphometric analysis of bat forelimb skeletal elements.
or•gan•ic | ôr'ganik | adjective. denoting a relation between elements of something such that they fit together harmoniously as necessary parts of a whole; characterized by continuous or natural development.
One of the…
pharyngula | April 18, 2006
It always gives a fellow a warm feeling to see an old comrade-in-arms publish a good paper. Chris Cretekos was a graduate student working on the molecular genetics of zebrafish at the University of Utah when I was a post-doc there, and he's a good guy I remember well…so I was glad to see his paper in Developmental Dynamics. But then I notice it wasn't on zebrafish—Apostate! Heretic!
Except…it's on bats. How cool is that? And it's on the embryonic development of bats. Even cooler! I must graciously forgive his defection from the zebrafish universe since he is working on an organism that is…
pharyngula | April 14, 2006Hapalochlaena maculosa
Figure from Cephalopods: A World Guide (amzn/b&n/abe/pwll), by Mark Norman.