Cold water turns these fish into girls, hot water turns them into boys. Ranma 1/2, anyone?
In some finned species, like the Atlantic silverside — as well as in many reptiles — sex is determined not by genetics but by temperature: the undifferentiated embryo develops testes or ovaries on the basis of whichever option conveys evolutionary advantages for that particular environment. Now, in a study published in the July 30 edition of the scientific journal Public Library of Science, Natalia Ospina-Alvarez and Francesc Piferrer have gone a little further in explaining how that mechanism works. In laboratory tests, they have demonstrated that higher water temperatures result in more male fish.
"We found that in fish that do have temperature-dependent sex determination [TSD], a rise in water temperature of just 1.5 degrees Celsius can change the male-to-female ratio from 1:1 to 3:1," says Piferrer, the study's co-author. In especially sensitive fish, a greater increase can throw the balance even more out of whack. Ospina-Alvarez and Piferrer have found that in the South American pejerrey, for example, an increase of 4 degrees Celsius can result in a population that is 98% male.
What makes these findings especially troubling, of course, is that the International Panel on Climate Change (IPCC) predicts that ocean-water temperatures are likely to rise by 1.5 degrees over the course of this century — and they may even go up a few degrees more. "If climate change really does result in a rise of 4 degrees, which is the maximum the IPCC predicts, and if species can't adapt in time or migrate, then in the most sensitive cases of TSD, we're looking at extinction," says Piferrer.( Collapse )Source