Parasite avoidance behaviours in aquatic environments

Parasites, including macroparasites, protists, fungi, bacteria and viruses, can
impose a heavy burden upon host animals. However, hosts are not without
defences. One aspect of host defence, behavioural avoidance, has been studied
in the terrestrial realmfor over 50 years, butwas first reported from the aquatic
environment approximately 20 years ago. Evidence has mounted on the
importance of parasite avoidance behaviours and it is increasingly apparent
that there are core similarities in the function and benefit of this defence
mechanism between terrestrial and aquatic systems. However, there are also
stark differences driven by the unique biotic and abiotic characteristics
of terrestrial and aquatic (marine and freshwater) environments. Here, we
review avoidance behaviours in a comparative framework and highlight the
characteristics of each environment that drive differences in the suite of
mechanisms and cues that animals use to avoid parasites. We then explore
trade-offs, potential negative effects of avoidance behaviour and the influence
of human activities on avoidance behaviours. We conclude that avoidance
behaviours are understudied in aquatic environments but can have significant
implications for disease ecology and epidemiology, especially considering the
accelerating emergence and re-emergence of parasites.
This article is part of the Theo Murphy meeting issue ‘Evolution of
pathogen and parasite avoidance behaviours’.