Crustacean giants because of oxygen

Scientists have the first proof that Antarctic crustaceans are giants because of increased oxygen availability rather than their low temperature environment as previously thought.

Reporting in this week's Nature, authors Gauthier Chapelle of the Institut Royal des Sciences Naturelles de Bruxelles and Professor Lloyd Peck of British Antarctic Survey explain how cold-blooded animals in polar regions are true giants.

Professor Peck says, "The largest Antarctic amphipod is, at 90mm and five times as long as its tropical cousin, indeed a true giant. For the last hundred years or so scientists believed that the phenomenon of giant species found in polar seas was related to the low temperatures and the reduced metabolic rates of the cold-blooded animals living there. However, we found that freshwater amphipods from Lake Baikal, Russia, were twice as large as those in the sea at the same temperature, leading us to conclude that their size could not be controlled by low temperature alone. We ran a series of analyses and found that the increased oxygen in the cold oceans and freshwater lakes meant bigger species could be produced. One implication of our work is in understanding the fossils of giant insects from the Carboniferous period. At that time the amount of oxygen in the atmosphere was 33% compared with the 20% we have today. Giant amphipods, and probably most polar giant species, are at the limit of their possible size. If global change reduces the available oxygen in the environment, or increases their requirement for oxygen we would predict that cold-blooded giant low-temperature species would be among the first to become extinct."