In order to escape predators, many fish – including insects, fish and birds – have developed strategies for rapidly transmitting information on threats to others of their species.
In order to escape predators, many fish – including insects, fish and birds – have developed strategies for rapidly transmitting information on threats to others of their species. This information is transmitted within a group of hundreds, or even thousands, of individuals in (escape) waves. This collective response is also, in the case of fish, known as shoal behaviour. Special parasites can, however, manipulate such a survival strategy. Researchers at the University of Münster have discovered that infected individual fish disturb the transmission of flight behaviour and, as a result, increase not only their own risk of being eaten, but also that of other – non-infected – members of the group. The results of the study have been published in the journal “Proceedings of the Royal Society”.
In order to study social responsiveness in fish, the researchers used the tapeworm Schistocephalus solidus as a parasite. The three-spined stickleback Gasterosteus aculeatus – an important model in ecological and evolutionary parasitology – was used as an intermediate host. The parasite ensures that the fish is less prone to be scared and more courageous and, as a result, increases its risk-taking behaviour. This poses the threat that the stickleback will very probably fall prey to the final host of the parasite, a fish-eating bird. In aquariums the scientists simulated a bird strike on shoals of sticklebacks. “When the shoal consisted only of healthy – in other words, non-infected – sticklebacks, the escape wave continued quickly through the entire shoal after the bird strike, even though the sticklebacks at the back were only able to see the response of their conspecifics and not the bird strike itself", explains Nicolle Demandt from the Institute of Evolution and Biodiversity at the University of Münster and lead author of the study. "When we placed infected sticklebacks in the middle of the shoal, the escape wave came to a virtual halt and it only got through to the fish at the back to a limited extent.”
Read more: University of Munster
Infection by parasites disturbs flight behaviour in shoals of fish. (Photo Credit: WWU/Jörn Scharsack)
