Laboratory of Behaviour of Lower Vertebrates, Institute of Ecology and Evolution, Russian Academy of Sciences, 33 Leninskii pr, 119071, Moscow, Russia.
Parasit Vectors. 2013 Oct 17;6(1):301. doi: 10.1186/1756-3305-6-301.
Parasite distribution is often highly heterogeneous, and intensity of infection depends, among other things, on how well hosts can avoid areas with a high concentration of parasites. We studied the role of fish behaviour in avoiding microhabitats with a high infection risk using Oncorhynchus mykiss and cercariae of Diplostomum pseudospathaceum as a model. Spatial distribution of parasites in experimental tanks was highly heterogeneous. We hypothesized that fish in groups are better at recognizing a parasitized area and avoiding it than solitary fish.
Number of fish, either solitary or in groups of 5, was recorded in different compartments of a shuttle tank where fish could make a choice between areas with different risk of being infected. Intensity of infection was assessed and compared with the number of fish recorded in the compartment with parasites and level of fish motility.
Both solitary fish and fish in groups avoided parasitized areas, but fish in groups avoided it more strongly and thus acquired significantly fewer parasites than solitary fish. Prevalence of infection among grouped and solitary fish was 66 and 92 %, respectively, with the mean abundance two times higher in the solitary fish. Between-individual variation in the number of parasites per fish was higher in the "groups" treatment (across all individuals) than in the "solitary" treatment. Avoidance behaviour was more efficient when fish were allowed to explore the experimental arena prior to parasite exposure. High motility of fish was shown to increase the acquisition of D. pseudospathaceum.
Fish in groups better avoided parasitized habitat, and acquired significantly fewer parasites than solitary fish. We suggest that fish in groups benefit from information about parasites gained from other members of a group. Grouping behaviour may be an efficient mechanism of parasite avoidance, together with individual behaviour and immune responses of fishes. Avoidance of habitats with a high parasite risk can be an important factor contributing to the evolution and maintenance of grouping behaviour in fish.
寄生虫的分布通常具有高度异质性，感染强度除其他因素外，还取决于宿主回避高寄生虫浓度区域的能力。我们以虹鳟鱼和双鳞盘口吸虫尾蚴为例，研究了鱼类行为在避免高感染风险小生境中的作用。实验水槽中的寄生虫空间分布高度异质。我们假设群体中的鱼类比单独的鱼类更善于识别被感染的区域并回避它。
在一个穿梭水槽的不同隔间中记录单独或 5 条一组的鱼的数量，鱼类可以在不同感染风险的区域之间做出选择。评估感染强度，并与记录有寄生虫的隔间中的鱼的数量以及鱼的运动水平进行比较。
单独的鱼和成群的鱼都回避了被感染的区域，但成群的鱼回避得更强烈，因此感染的寄生虫数量明显少于单独的鱼。成群鱼和单独鱼的感染率分别为 66%和 92%，单独鱼的平均丰度高两倍。在“群体”处理（所有个体）中，每条鱼的寄生虫数量个体间差异高于“单独”处理。在暴露于寄生虫之前允许鱼类探索实验场地时，回避行为更为有效。鱼类的高运动性被证明会增加双鳞盘口吸虫的获取。
成群的鱼比单独的鱼更好地回避了被感染的栖息地，感染的寄生虫数量明显减少。我们认为，群体中的鱼类从群体中的其他成员那里获得了关于寄生虫的信息，从而受益。与鱼类的个体行为和免疫反应一起，群体行为可能是避免寄生虫的有效机制。回避高寄生虫风险的栖息地可能是鱼类群体行为进化和维持的一个重要因素。
