Enteroctopus dofleini, the giant Pacific octopus
Figure from Cephalopods: A World Guide (amzn/b&n/abe/pwll), by Mark Norman.
Pharyngula
Evolution, development, and random biological ejaculations from a godless liberal
Jason Rosenhouse has dug into the details of the evo-devo chapter of Behe’s The Edge of Evolution and found some clear examples of dishonest quote-mining (so what else is new, you may be thinking—it’s what creationists do). I’ve warned you all before that when you see an ellipsis in a creationist quote, you ought to just assume that there’s been something cut out that completely contradicts the point the creationist is making; Rosenhouse finds that Behe gets around that little red-flag problem by simply leaving out the ellipses.
I just want to expand a little bit on one point Behe mangles and that Jason quotes. It turns out I actually give a lecture in my developmental biology courses on this very issue, the mathematical modeling antecedents to insect segmentation, so it’s simply weird to see Behe twisting a subject around that is so well understood in the evo-devo community, and that was actually well explained in Sean Carroll’s Endless Forms Most Beautiful.
Oooooh, with lots of pictures. I hope you’re into chitin and legs.
This is Gigantoraptor erlianensis, a newly described oviraptorosaur from late Cretaceous of China. It’s a kind of nightmare version of Big Bird — it’s estimated to have weighed about 1400kg (1½ tons for non-metric Americans).
Histological examination of the growth structure of the bones suggests that this fellow was a young adult, about 11 years old, and that they grew rapidly and reached nearly this size by the time they were 7. And since it is a young adult, there were probably bigger gigantoraptors running around. They also compared limb length to other dinosaurs, like the tyrannosaurs—gigantoraptor had longer, slimmer legs and was more of a runner than they were.
There’s no sign whether it was covered with bright yellow feathers.
Xu X, Tan Q, Wang J, Zhao X, Tan L (2007) A gigantic bird-like dinosaur from the Late Cretaceous of China. Nature advance online publication, 13 June 2007.
Since I asked for it, and since so many were promptly forthcoming with a copy, I’d better give you a quick summary. Kubodera et al. have formally published their observations of the eight-armed deep sea squid, Taningia danae, that were in the news last February. There isn’t much new information in the papers; it’s all based on a handful of video observations of hunting squid in their native habitat, so it’s more on the side of anecdote than anything else right now. It’s still just plain cool.
That photo is of their video gear. It’s a platform with lights and cameras that’s lowered on a cable to almost a thousand meters. What I thought was cute, though, was that object jutting off at about 45°—that’s a fiberglas fishing pole with a short length of monofilament line dangling the bait in front of the cameras. It’s so jaunty to strap a pole to your robot and send it off to go fishing.
No, actually they don’t — but they do have some proteins that are essential components of synapses, and it tells us something important about the evolution of the nervous system. A new paper by Sakarya et al. really isn’t particularly revolutionary, but it is very interesting, and it does confirm something many of us suspected.
The initial change from camouflaged to conspicuous takes only milliseconds due to direct neural control of the skin. Full expression of the threat display (right) is two seconds. Video frame rate is 30 frames per second. Watch the video clip.
Everyone here is familiar with the incredible ability of cephalopods to change their appearance, right? If you aren’t, review your cuttlefish anatomy and watch this video. A few frames from the video are shown on the right.
This is an amazing ability, and the question is how do they do it? Roger Hanlon has been spending years tinkering with cephalopods, trying to puzzle it out and come up with an explanation. There are a couple of things a master of disguise needs.
A good visual system. To match the background, you need to be able to see the background at least as well as the predator trying to see you.
Fast connections to the effector organs. Cephalopods have motor nerves that go straight from their brains to the chromatophore organs with no synaptic delays along the way.
The hard part: cutaneous chromatophore organs that can change intensity and texture with a fair amount of spatial resolution. Cephalopods have tiny, discrete sacs of pigment scattered all over their body, each one ringed with muscles that can iris shut to conceal the pigment, or expand the sac to expose the pigment. There are also muscular papillae that work hydrostatically to change the texture of the skin from smooth to rough to spiny/spiky.
An algorithm. A set of rules that translate a visual field into an effective skin pattern that hides the animal.
One of the minor surprises of this work is that that last item, the algorithm for generating camouflage, may not be that complex. By studying many camouflaged organisms, they’ve categorized camouflage techniques into just three different strategies.
