Goldfish in icy ponds hold key to foetal alcohol syndrome

Jesus famously turned water into wine, and now it looks like goldfish routinely do the same thing to survive in icy ponds, a new study has shown...

Goldfish are extremely resilient and can survive for months when the pond they live in freezes over and deprives them of access to oxygen.

Under these conditions, the oxygen levels fall to near zero, which kills the majority of fish, but not goldfish or their close crucian carp relatives. So how do they survive?

The unlikely answer is that they churn out alcohol! A chance genetic mutation in an ancestor endowed these fish with a duplicate set of genes involved in energy production.

One of these sets they have adapted and turned into biochemical machinery that turns on under the right conditions and converts a toxic metabolic waste product called lactic acid, which cells make when they are starved of oxygen, into ethanol. This is carried in the bloodstream to the gills where it leaches out into the surrounding pond water.

The process means that the fish are able to survive for extended periods of time, which can be months, without any oxygen, and rid themselves of poisonous lactic acid, which is the chemical that accumulates painfully in our muscles during a stiff workout.

The price the animals pay for this extraordinary ability is that it's tremendously wasteful in energy terms, but given the alternative - certain death, it's attractive all the same. It's also attractive to researchers like Liverpool University's Michael Berenbrink, who fathomed out how it works and published the work this week in Scientific Reports, because it might reveal new ways to prevent the toxic effects of alcohol in the body.

"These fish survive for months with blood alcohol levels way above the drink driving limit in many countries! That would severely damage the livers of humans, but the animals are not harmed. If we can find out how, and why, then we may be able to help individuals like babies at risk from foetal alcohol syndrome, or problem drinkers..."

However, thirsty tipplers who may be considering setting up their own back-yard brewery to churn out pond-based alcoholic beverages will be disappointed. "The amount of alcohol each fish makes is tiny," says Berenbrink. "A goldfish would take 200 days to produce an alcohol concentration equivalent to a beer just in a small glass! The animal itself though would still have a very high blood alcohol concentration, considerably above the drink drive limit..."

So goldfish should absolutely not drive their "motor-pikes" in winter...