Researchers have solved the mystery of how crucian carp manage to survive for months at a time in water without oxygen.

Carp are highly vulnerable to predation and one survival strategy they employ is to inhabit seasonally anoxic (low oxygen) ponds where predators are unable to survive.

A drop in water temperature prompts the carp to store vast amounts of glycogen in their brains, the researchers found. This enables them to make the switch to anaerobic metabolism – which does not require oxygen – from February to April in the northern hemisphere.

“Carp use carbohydrates stored as glycogen as a source of energy during anoxic conditions,” says principal researcher Matti Vornanen at the University of Joensuu, Finland. They break down the stored glycogen into glucose and ethanol, providing the energy they need to survive, he explains.

http://www.newscientist.com/article/...gh-winter.html