Velvet worms, living fossils that look like a child's rendition of caterpillars, are more closely related to spiders and scorpions than to butterflies, according to new research.
Known to scientists as onychophorans, velvet worms have been thought to be similar to the ancestors of modern arthropods, the jointed-legged creatures that includes insects.
Fossils that look very much like today's onychophorans can be found in rocks 540 million years old.
"When I looked at their brains, I was shocked because I didn't expect to see what I saw," said Nicholas J. Strausfeld of The University of Arizona in Tucson. "I just felt from their organization that these looked like spider brains, that they had more in common with spider brains than with other arthropod brains."
Strausfeld, a UA Regents' Professor of neurobiology and the director of UA's Center for Insect Science, is a pioneer in using the architectures of cell arrangements within brains to tease out evolutionary relationships among arthropods, the animal phylum that includes all kinds of creepy crawlies, including insects, crustaceans such as lobsters and crabs, and spiders and scorpions.
Onychophora live in groups, defend territories and subdue their prey with sticky goo. The small, sometimes brightly colored, worm-like carnivorous creatures have lobed appendages and live in leaf litter in tropical areas.
"They are very difficult to approach with a pair of forceps because they squirt out this gluey substance that bungs up one's dissection tools. In the wild they use it to immobilize their prey," Strausfeld said of the 2-inch-long critters. "They're really quite extraordinary."
Strausfeld and his colleagues compared the brain architecture of onychophorans with a range of arthropods, including spiders, scorpions, dragonflies, bees, crabs, shrimps and centipedes.
"There are certain ground rules that seem to apply to all brain structures
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Contact: Mari N. Jensen
mnjensen@email.arizona.edu
520-626-9635
University of Arizona
24-Jul-2006