Goldfish make alcohol to survive harsh winters

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Goldfish make alcohol to survive harsh winters

August 13, 2017 - 10:40
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Every winter, the goldfish and crucian carp survive the winter at the bottom of ice-covered lakes in water devoid of oxygen. How do they do this?

Perhaps not quite in this fashion but still

Scientists from the Universities of Oslo and Liverpool have discovered their secret. Simply put, the fish produces alcohol in its body.

In zero-oxygen environments, the body switches to anaerobic respiration, a process in which carbohydrates are converted into energy. This process can only be sustained for a short time, as in the case of human sprinters. After that, lactic acid accumulates in the body, and too much of it is harmful to the body.

The fish can avoid this because they have two—not one—sets of proteins used to channel the carbohydrates to the mitochondria, where energy is produced. Although one of the sets appear to be similar to that of other species, the other set of proteins appears to be a mutation that prompts the fish’s body to release only ethanol—not lactic acid—through fermentation.

“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,” said Dr Michael Berenbrink, an evolutionary physiologist at the University of Liverpool.

“However, this is still a much better situation than filling up with lactic acid, which is the metabolic end product for other vertebrates, including humans, when devoid of oxygen,” he added.

After sequencing the animal’s DNA, the researchers discovered that the evolution of the two sets of proteins took place eight million years ago, in a species that was the common ancestor of the goldfish and crucian carp.

Lead author Dr Cathrine Elisabeth Fagernes, from the University of Oslo, elaborated, “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 was thus not surprising that the goldfish, as the crucian carp’s cousin, is one of the most resilient pets around, she added.

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