Last year I went to a fascinating symposium in honor of the great evolutionary biologist George Williams. The March issue of the Quarterly Review of Biology ran a series of papers written by the speakers at the meeting that offered much more detail on how Williams had influenced them in their various fields. Randolph Nesse of the University of Michigan gave one of the most interesting talks at the meeting on maladaptation and what it means to human medicine. You can download the pdf from his web site.
Back in 1986 a biologist named Cindy Lee Van Dover was poking around the innards of shrimp from the bottom of the sea. They came from a hydrothermal vent in the Atlantic, where boiling, mineral-rich water came spewing up from cracks in the Earth’s crust and supported rich ecosystems of tube-worms, microbes, crabs, and other creatures. The animals that lived around these vents were generally blind, which wasn’t surprising considering that no sunlight could reach them. But Van Dover noticed that they had two flaps of tissue running along their backs that connected to nerves. Closer inspection revealed that the tissue was actually made of light-sensitive pigments and photoreceptors. What, Van Dover wondered, could these shrimp possibly be looking at. Dives to mid-ocean ridges later revealed that the vents produce a faint light of their own.
The New York Times, June 21, 2005
Jellyfish have traditionally been considered simple and primitive. When you gaze at one in an aquarium tank, it is not hard to see why.
Like its relatives the sea anemone and coral, the jellyfish looks like a no-frills animal. It has no head, no back or front, no left or right sides, no legs or fins. It has no heart. Its gut is a blind pouch rather than a tube, so its mouth must serve as its anus. Instead of a brain, it has a diffuse net of nerves.
A fish or a shrimp may move quickly in a determined swim; a jellyfish pulses lazily along.
Continue reading “Plain, Simple, Primitive? Not the Jellyfish”
I’ve got an article in today’s New York Times about jellyfish and their kin—known as cnidarians. Cnidarians look pretty simple, which helped earn them a reputation as simple and primitive compared to vertebrates like us, as well as insects, squid, and other creatures with heads and tails, eyes, and so on (known as bilaterians). But it turns out that a lot of the genes that map our complex anatomy are lurking in cnidarians, too. Scientists are now pondering what all that genetic complexity does for the cnidarians. They’re also using these findings to get a better idea of how the major groups of animals evolved between 600 and 500 million years ago.