Abstract
BackgroundIndividuals have to trade-off the costs and benefits of group membership during shoaling behaviour. Shoaling can increase the risk of parasite transmission, but this cost has rarely been quantified experimentally. Guppies (Poecilia reticulata) are a model system for behavioural studies, and they are commonly infected by gyrodactylid parasites, notorious fish pathogens that are directly transmitted between guppy hosts.Methodology/Principal FindingsParasite transmission in single sex shoals of male and female guppies were observed using an experimental infection of Gyrodactylus turnbulli. Parasite transmission was affected by sex-specific differences in host behaviour, and significantly more parasites were transmitted when fish had more frequent and more prolonged contact with each other. Females shoaled significantly more than males and had a four times higher risk to contract an infection.Conclusions/SignificanceIntersexual differences in host behaviours such as shoaling are driven by differences in natural and sexual selection experienced by both sexes. Here we show that the potential benefits of an increased shoaling tendency are traded off against increased risks of contracting an infectious parasite in a group-living species.
Highlights
Social aggregation of fish, or shoaling behaviour, involves individuals trading-off the costs and benefits of group membership [1]
Competition for resources increases with group size [7], and a number of studies have documented an increase in risktaking behaviour with increased shoal size (e.g., [3])
As predicted from Griffiths and Magurran [19], female guppies shoaled significantly more than males. This resulted in focal females passing on their infection to non-focal conspecifics more readily than focal males in single sex shoals
Summary
Shoaling behaviour, involves individuals trading-off the costs and benefits of group membership [1]. Many parasites have been assessed for their impact on fish behaviour (reviewed in [9]) but only a limited number of studies have considered the reverse situation, i.e. the direct impact of shoaling behaviour on parasite transmission [12], [13], [14] This latter study [14] found that for some groups of parasites, shoaling host species harboured significantly greater parasite diversity than solitary host species, but this pattern did not hold for directly transmitted parasites. A ubiquitous and highly contagious group of fish parasites are the gyrodactylid monogeneans They are directly transmitted but the possible influence of host shoaling behaviour on their transmission has never been examined. Guppies (Poecilia reticulata) are a model system for behavioural studies, and they are commonly infected by gyrodactylid parasites, notorious fish pathogens that are directly transmitted between guppy hosts
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