Extreme Environment Changes Fish Appearance

The Devils Hole pupfish is one of the most endangered species of fish in the world, because in the wild the entire species lives only in a single rocky pool in Death Valley in California. Now scientists have discovered that the Devils Hole pupfish, a little inch long fish, look the way they do partly because of their tiny cramped conditions. Some of the wild pupfish were transferred to captivity to help try and ensure the species survival should the natural population in the Devils Hole die out, but the pupfish bred in refuges have begun to look rather different to their wild brothers and sisters with deeper bodies and smaller heads. This change in the appearance of captive-bred fish raises serious questions about how this rare species can be protected from extinction. Sean Lema and Gabrielle Nevitt from the University of California Davis, set about trying to understand how environment changes could affect the way pupfish look. They worked in the lab with a similar but unthreatened species called Amargosa pupfish - and to mimic the conditions in Devils Hole they warmed the tank water up and restricted the amount of food the fish could eat. And low and behold, the Amargosa pupfish started to look more like the wild Devils Hole pupfish. On the positive side, these studies suggest that fish may be more adaptable to changing conditions than was previously thought - but also it could mean that captive-bred pupfish could die if they were reintroduced into the Devils Hole in Death Valley to try and rebuild the wild population. And this also raises a slightly philosophical question, that if the way an animal looks is so intimately linked to its environment, is it still the same fish if it is not preserved in the same habitat? So does keeping Devils Hole pupfish alive in captivity really mean anything if there are none left in the wild?