Climate change is about to deal a double evolutionary deal on a group of Antarctic animals that have adapted well to the icy environment only to lose out to global warming. They have developed an anti-freeze glycoprotein (AFGP) in their blood 22 to 42 million years ago. Now, for three species in the family Notthenioidae, a bleak outlook once again threatens.

With the rapid rise in polar temperatures, "A rise of 2 o C in water temperature will likely have a devastating impact on this Antarctic fish lineage, which is so well adapted to water at freezing temperatures," said Thomas J. Near, associate professor at Yale and lead author of the study published online on Feb. 13 in the Proceedings of the National Academy of Sciences (PNAS).

The whole family of 100 species make the Antarctic a diverse marine environment, together with discoveries still being made beneath the ice caps. Penguins, seals and whales occupy top predator niches while the phytoplankton blooms are the source of energy. As well as the antifreeze, these fish adapted in several other ways to their precious habitats, but these very adaptations prevent them from adapting quickly to a warming environment.

Molecular phylogeny is a new science well equipped to investigate how global cooling, 35 million years ago, created adaptive radiations in this family. Speciation accelerated 10 million years after the first AFGP developed. This was during the late Miocene up to 5.3 million years ago, when the Southern Ocean became as icy as it was recently (before global warming). Now it is revealed that this whole family of fish could be removed from the food chains that sustain the Antarctic environment. It is not only the outlook for the ice fish that's bleak.