School of Biosciences, Cardiff University, Cardiff, United Kingdom.
PLoS One. 2010 Oct 11;5(10):e13285. doi: 10.1371/journal.pone.0013285.
Individuals 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 FINDINGS: Parasite 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/SIGNIFICANCE: Intersexual 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.
个体在群体行为中必须权衡群体成员身份的成本和收益。群体聚集会增加寄生虫传播的风险，但这种成本很少通过实验进行量化。孔雀鱼（Poecilia reticulata）是行为研究的模式生物系统，它们通常被旋盘虫科寄生虫感染，旋盘虫是臭名昭著的鱼类病原体，在孔雀鱼宿主之间直接传播。
方法/主要发现：使用Gyrodactylus turnbulli 的实验感染观察了雄性和雌性孔雀鱼单性鱼群中的寄生虫传播。寄生虫的传播受到宿主行为中性别特异性差异的影响，当鱼之间的接触更加频繁和持久时，寄生虫的传播显著增加。雌性鱼的群体聚集程度显著高于雄性鱼，感染的风险高四倍。
结论/意义：两性之间的宿主行为差异（如群体聚集）是由两性经历的自然选择和性选择差异驱动的。在这里，我们表明，在群居物种中，增加群体聚集倾向的潜在好处是与增加感染传染性寄生虫的风险相权衡的。
