While humans and other vertebrate animals die within a few minutes without air, goldfish and their wild relative the crucian carp can survive for months without oxygen.
The ability to survive such conditions stems from an additional set of proteins normally used to steer carbohydrates toward breaking down within a cell’s mitochondria, which the fish use to convert anaerobically produced lactic acid into alcohol, according to a study published Friday in the journal Scientific Reports.
The process, which is unique among vertebrates, is more commonly associated with brewer’s yeast.
“During their time in oxygen-free water in ice-covered ponds, which can last for several months in their northern European habitat, blood alcohol concentrations in crucian carp can reach more than 50 mg per 100 milliliters, which is above the drink-drive limit in these countries,” said study co-author Michael Berenbrink, an evolutionary biologist at the University of Liverpool.
In other words, the goldfish make themselves drunk, for months on end.
The unique ability results from a whole genome duplication – an event that creates an organism with additional copies of the entire genome of a species – in a common ancestor of goldfish and crucian carp, which occurred about 8 million years ago, according to genetic analyses.
“This research emphasizes the role of whole genome duplications in the evolution of biological novelty and the adaptation of species to previously inhospitable environments,” said lead author Cathrine Elisabeth Fagernes, an administrative manager at the University of Oslo.
The mechanism also allows the fish to avoid competition for food from other species, as well as predators.
“It’s no wonder then that the crucian carp’s cousin the goldfish is arguably one of the most resilient pets under human care,” Fagernes said.