Many fish, like butterflies and moths, produce large eye spots on their less vulnerable parts, apparently so that predators will attack there and give them a better chance to escape in an unexpected direction. At worst they may suffer less damage.
However, there is substantial variation in the size of these spots, even within a species. When James Cook University graduate student Oona Lönnstedt placed damselfish in a range of different conditions she found the spots changed with the circumstances.
“We found that when young damsel fish were placed in a specially built tank where they could see and smell predatory fish without being attacked, they automatically began to grow a bigger eye spot, and their real eye became relatively smaller, compared with damsels exposed only to herbivorous fish, or isolated ones,” Lönnstedt says. Fish that could see or smell predators had a similar response, while fish exposed to herbivorous fish or no fish at all kept their false eyes small and their real eyes large.
The frightened damselfish also changed their body shape, growing wider and shorter, apparently to be harder to swallow, as well as taking refuge more often. Once released into the wild, Lönnstedt announced in Scientific Reports that the predator-exposed fish tended to survive longer.
Lönnstedt’s supervisor, Dr Mark McCormick, admits that some aspects...
