Evolution: Biology's next top model?

Abstract

From Antarctic icefish to Galapagos finches, there are some interesting characters at the fringes of developmental biology. Brendan Maher explores a world of alternative model organisms. As the water temperatures plunged by about 5 �C to below zero over the next few million years, most fish became extinct or moved on to warmer climes. But one group, the Notothenioidei, remained. Thanks to some extraordinary evolutionary innovations, these bottom-dwellers radiated, speciated and ultimately dominated. Crucial proteins shifted shape so they could work at cold temperatures, and a digestive enzyme fragment took on a new role as antifreeze. Because colder waters hold more dissolved oxygen, red blood cells became dispensable, and the 16 species of the Channichthyidae family no longer make them at all. These are the icefish of the Antarctic: clear blooded, up to almost a metre long and with eerie, crocodilian features.