fish-bowl-goldfishAs many of you know from personal experience a little alcohol during some winter activity gives a nice sensation of warmth, as blood vessels on the skin’s surface open.  Actually, alcohol doesn’t help raise the body’s temperature and it sure doesn’t help us breathe in an oxygen deprived environment.  Yet somehow goldfish and their wild relatives, crucian carp, can survive for up to months at a time, at the bottom of ice-covered ponds in water deprived of oxygen.  Scientists at the Universities of Oslo and Liverpool have found the secret behind the goldfish’s remarkable ability to survive these harsh frozen water conditions and it is “home brewed” alcohol.

The study found that Goldfish have a special adaptation to produce ethanol which they vent into the water through their gills.  When the goldfish runs out of oxygen in these harsh conditions the brewing process starts as the fish are able to convert anaerobically produced lactic acid into ethanol.  In the paper published in the journal Scientific Reports, the international team has shown that muscles of goldfish and crucian carp contain not just the usual one, but two sets of the proteins used for energy production.  This second set produces an enzyme called pyruvate decarboxylase, which gets triggered in low-oxygen environments, to guarantee the goldfish only eliminate ethanol through fermentation, rather than hazardous lactic acids.

Dr Michael Berenbrink, an evolutionary physiologist at the University of Liverpool, said: “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 millilitres, which is above the drink drive limit in these countries.

Lead author Dr. Cathrine Elisabeth Fagernes, from the University of Oslo, followed with:

“The ethanol production allows the crucian carp to be the only fish species surviving and exploiting these harsh environments, thereby avoiding competition and escaping predation by other fish species with which they normally interact in better oxygenated waters.”

“It’s no wonder then that the goldfish is arguably one of the most resilient pets under human care.”