By Sarah Kaplan
In the 1870s, a German anatomist named Karl Gegenbaur had an idea.
The gill arches of certain fish (gill arches are bony structures that support — you got it — the gills) had appendages that seemed to branch out like fingers. Perhaps, Gegenbaur theorized, these arches were the evolutionary precursor to fish fins and land-dwellers’ limbs.
It was an interesting notion, but the fossil record didn’t seem to bear it out. Gegenbaur’s theory might have been consigned to the “weird things scientists thought in the 19th century” column — along with “rain follows the plow” and the entire field of phrenology — were it not for modern biology, a gene known as the sonic hedgehog and a slimy-looking, dinner plate-sized ray called the little skate.
All three come together in a paper published this week in the journal Development that hints at redemption for Gegenbaur’s century-old proposal. By studying the development of little skate embryos, biologists Andrew Gillis and Brian Hall found that the skates use the same genetic tool to build their gill arches that some fish, humans and other land creatures deploy when developing fins and legs.
“What this suggests is that the genetic program underlying the gill arches may be the same program underlying limb development,” said Gillis, a developmental biologist at the University of Cambridge and the Marine Biological Laboratory in Woods Hole, Mass. Read more …