A new study has found that fish may experience â€˜emotional feverâ€™, which has been used as a basis for proving sentience or consciousness in other species. Until now many experts have seen fish as not being sentient beings in the same way as mammals and birds.
A state of emotional fever is an elevation of body temperature of one or two degrees in response to stress, and it is regarded as a hallmark of sentience and consciousness.
Researchers working with Zebra danios exposed 36 fish held in a net to water 1°C than they are used to, while a control group of the same number were left swimming at normal temperatures. All the fish were then transferred to an aquarium with six interconnected chambers, each with a different temperature, where they were allowed to swim about of their own accord.
The scientists found that the recently stressed fish consistently congregated in the heated sections of the tank, raising their body temperatures from 2–4°C above that of the unstressed fish, which may shown emotional fever.
The scientists say: "This finding removes a key argument for lack of consciousness in fishes."
Researchers published their findings in the journal Proceedings of the Royal Society B.
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