Organisms
pharyngula | August 10, 2007Histioteuthis heteropsis
Figure from The Deep(amzn/b&n/abe/pwll), by Claire Nouvian.
pharyngula | August 9, 2007Two new Homo fossils are described in this week's Nature, and here they are.
This is KNM-ER 42700. It's a very well preserved brain case, it has been dated to 1.55 million years ago, and it has been positively identified as belonging to Homo erectus. It's a little unusual in being particularly small, but otherwise, definitely H. erectus.
a, Anterior, b, left lateral, d, superior and e, inferior views of KNM-ER 42700 (scale bar, 5 cm).
This is KNM-ER 42703. It's a broken maxilla, or upper jaw, and it has been dated to 1.44 million years ago — it's over 100,000 years more recent than the KNM-…
pharyngula | August 8, 2007Some two-bit publicity hound can die, and that's all you can find on any of the television channels … a whole grand species can go extinct, and there's almost nothing.
Say goodbye to the Yangtze River dolphin. It is officially extinct. The funeral will be poorly attended, and it will be forgotten, except in a few academic papers.
pharyngula | August 3, 2007Macrotritopus larva
Figure from Cephalopods: A World Guide (amzn/b&n/abe/pwll), by Mark Norman.
pharyngula | August 1, 2007Since I was asked what a cnidarian "head" is in reference to this work on multi-headed cnidarians, I'll answer. In short, they don't have one.
Longer answer: the paper in PLoS describes a procedure for generating homeotic mutations in cnidarians by manipulating the expression of Cnox genes in hydrozoans. Knock outs of various cnidarian Hox-like genes and the medusae develop extra manubriae, or the tentacled part at the oral end of the animal, which the authors colloquially call "heads" (and they do usually put the word in quotes). These structures aren't homologous to the things we consider…
pharyngula | August 1, 2007
It's a collision! Two great carnivals on the same day. Check out Carnival of the Spineless #23 from sodden Great Britain, where the molluscs are thriving, and also read Tangled Bank #85, the Reductionist's Tale at Migrations.
pharyngula | July 31, 2007This is a short video clip of myotome formation in a zebrafish embryo — it's the subject of an upcoming column in Seed, so I'm putting a short visual aid here.
You can Download the Quicktime movie (620K), or you can watch it via YouTube. Watch closely, it's short and it flies by!
If you're totally mystified still, let me orient you. Here's a whole zebrafish embryo. There's a large yolk filling most of the center of the image, and the embryo itself arcs along the dorsal side, stretching from where I've labeled the eye to the tailbud.
Along the length of the trunk, you might be able to see…
pharyngula | July 30, 2007
People are always arguing about whether primitive apes could have evolved into men, but that one seems obvious to me: of course they did! The resemblances are simply too close, so that questioning it always seems silly. One interesting and more difficult question is how oysters could be related to squid; one's a flat, sessile blob with a hard shell, and the other is a jet-propelled active predator with eyes and tentacles. Any family resemblance is almost completely lost in their long and divergent evolutionary history (although I do notice some unity of flavor among the various molluscs,…
pharyngula | July 29, 2007
A little knowledge would short circuit a lot of strange speculation. That picture to the right is of a shark caught in Malaysia, and people are calling those odd dangly bits "legs". Despite the fact that someone said what they actually are in a comment early on, there are people arguing both that a shark with legs is evidence for evolution, and that it is evidence for creation.
They're both wrong.
It's a male shark. Those are the shark's claspers, or intromittent organs. The shark does the usual act you'd expect with a female of the species, and like many shark species, it has clasper spurs…
pharyngula | July 26, 2007A few years ago, everyone was in a tizzy over the discovery of Flores Man, curious hominin remains found on an Indonesian island that had a number of astonishing features: they were relatively recent, less than 20,000 years old; they were not modern humans, but of unsettled affinity, with some even arguing that they were like australopithecines; and just as weird, they were tiny, a people only about 3 feet tall with a cranial capacity comparable to a chimpanzee's. This was sensational. Then on top of that, add more controversy with some people claiming that the investigators had it all wrong…
pharyngula | July 25, 2007Next time GrrlScientist comes to visit, we're going to have to record what she says early in the morning, and then play it back ten times faster — I have a suspicion that we'll hear birdsong.
At least, that's the way this video art installation by Marcus Coates works. He had people sing strange little nonsense tunes (you can hear one here) that, when played back at a greater speed, recreated the songs of wild British birds. Why, if GrrlScientist had only talked a little faster, I'm sure the whole house would have sounded like an exotic tropical island inhabited by parrots!
pharyngula | July 14, 2007It's like a flood of papers on that curious cnidarian worm, Buddenbrockia. Now you can also read about its thoroughly bizarre pattern of development — there are unicellular amoeboids, plasmodial masses, and syncytia involved, so be prepared to be titillated.
pharyngula | July 13, 2007
If you've been reading that fascinating graphic novel, Y: The Last Man(amzn/b&n/abe/pwll), you know the premise: a mysterious disease has swept over the planet and bloodily killed every male mammal except two, a human named Yorick and a monkey named Ampersand. Substantial parts of it are biologically nearly impossible: the wide cross-species susceptibility, the near instantaneous lethality, and the simultaneity of its effect everywhere (there are also all kinds of weird correlations with other sort of magical putative causes, which may be red herrings). On the other hand, the…
pharyngula | July 13, 2007Mastigoteuthis sp.
Since I recently pointed out the strange news reports of an "octosquid" that even went so far as to call it half squid/half octopus, I thought I'd show why the preliminary assignment to the genus Mastigoteuthis was suggestive. It probably did have 8 arms and 2 tentacles … before it got sucked up in a pipe and flung to the surface. Those two feeding tentacles are delicate.
Figure from Cephalopods: A World Guide (amzn/b&n/abe/pwll), by Mark Norman.
pharyngula | July 12, 2007
Sometimes, I confess, this whole common descent thing gets in the way and is really annoying. What we've learned over the years is that the evolution of life on earth is constrained by historical factors at every turn; every animal bears this wonderfully powerful toolbox of common developmental genes, inherited from pre-Cambrian ancestors, and it's getting rather predictable that every time you open up some fundamental aspect of developmental pattern formation in a zebrafish, for instance, it is a modified echo of something we also see in a fruit fly. Sometimes you just want to see what…
pharyngula | July 11, 2007Usually, on my morning walk, I keep my eyes open for any squid that might have washed up on the sidewalks of Morris. Now I learn that the squid wash up on the beaches of Tasmania. I suppose a place nearer an ocean is a more likely spot. (By the way, TONMO is the site to check for more news on the beached squid carcass—and they think it is unlikely that it's actually a giant squid.)
Maybe I should start scanning for dead baby mammoths, instead.
pharyngula | July 10, 2007We now have a draft of the sea anemone genome, and it is revealing tantalizing details of metazoan evolution. The subject is the starlet anemone, Nematostella vectensis, a beautiful little animal that is also an up-and-coming star of developmental biology research.
(click for larger image)Nematostella development. a. unfertilized egg (~200 micron diameter) with sperm head; b. early cleavage stage; c. blastula; d. gastrula; e. planula; f. juvenile polyp; g. adult stained with DAPI to show nematocysts with a zoom in on the tentacle in the inset; h, i. confocal images of a tentacle bud stage and…
pharyngula | July 6, 2007Euprymna tasmanica mating pair (male on the left)
Figure from Cephalopods: A World Guide (amzn/b&n/abe/pwll), by Mark Norman.
pharyngula | July 6, 2007Euprymna tasmanica
Figure from Cephalopods: A World Guide (amzn/b&n/abe/pwll), by Mark Norman.