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Research has found how goldfish and their wild relatives, crucian carps, are able to survive winter.
Scientists have long known that goldfish can survive in extremely low temperatures, as seen in wild carps living in areas where lakes freeze in winter. In a recent discovery, researchers found that the fish survive in frozen environments by producing alcohol.
When lakes freeze, goldfish and wild carps become exposed to an oxygen-deprived environment. Oxygen is necessary for humans and most animals to produce heat and energy. Without it, producing heat and energy will also produce toxic lactic acid, which becomes deadly if not released by the body.
Staying without oxygen for too long can kill humans and other animals, but goldfish and carps were able to adapt to the inhospitable conditions of their habitat. These fish evolved with the ability to convert lactic acid into alcohol, which is thinner and can easily escape their body. The ability to release these toxic substances allows them to survive in cold areas with little oxygen for months, where humans would survive only for minutes.
However, some humans have also developed ways to live in high-altitude areas where there are low levels of oxygen. For instance, those who live in the Andes / ˈæn diz / Mountains developed the ability to carry more oxygen in their blood. Tibetans, on the other hand, were discovered to have fewer oxygen-carriers in their blood. Scientists hypothesize that this is to prevent them from having problems common to high altitudes, such as blood clotting and stroke. Aside from this, Tibetans were also found to breathe more frequently than those who live in normal altitudes.