群落中的高物种多样性可能会降低传染病的风险,被称为稀释效应。然而,稀释效应在不同疾病系统中的普遍性仍存在争议,因为宿主能力和宿主行为可能在疾病的稀释或放大中起作用。使用金鱼(Carassiusauratus)-单系外寄生虫(Gyrodactyluskobayashii)系统,在保持局灶性宿主密度恒定的情况下,研究了宿主能力和就学行为对寄生虫传播的影响。经过12种鱼类作为寄生虫潜在宿主的能力测试,G.kobayashii的感染是根据它们的寄主能力水平在与三种不同物种混合的金鱼鳍上确定的,包括普鲁士鲤鱼,CarassiusGibelio(低能力),草鱼,Ctenopharyngodonidellus(无能力),剑尾,Xiphophorushelleri(无能力),和四个物种的结合。与对照组金鱼的平均丰度(85.8±25.1)相比,与10条普鲁士鲤鱼配对时,金鱼的平均丰度显着降低(30.0±16.5),但与10个剑尾(70.0±22.2)配对时没有显着差异,10只草鱼(116.1±33.2),或者三种普鲁士鲤鱼的多种,在11天的实验中,有4只草鱼和3只剑尾鱼(75.9±30.8)。在普鲁士鲤鱼组和多物种组中的普鲁士鲤鱼上也发现了寄生虫,平均丰度分别为7.1和10.9。录像显示,金鱼与普鲁士鲤鱼混合得很好,当它们混合在一起时,它们与草鱼和剑尾鱼保持分离。金鱼之间的距离增加了,游泳速度和接触时间随着所有组其他鱼类的增加而减少。结果表明,由于相遇减少,存在足够数量的低能力宿主是稀释效应的必要条件,在低能力宿主的情况下,金鱼的教育行为的变化也可能增强稀释效应。然而,由于寄生虫的特殊性质以及缺乏与金鱼群的混合,无能力宿主的存在不会导致任何稀释作用。
High species diversity in a community may reduce the risk of infectious disease, termed the dilution effect. However, the generality of the dilution effect in different disease systems remains controversial as both host competence and behaviors of hosts may play roles in dilution or amplification of disease. Using the goldfish (Carassius auratus)-monogenean ectoparasite (Gyrodactylus kobayashii) system, effects of host competence and schooling behavior on parasite transmission were investigated while holding focal host density constant. Following competency tests of 12 fish species as potential hosts for the parasite, infection by G. kobayashii was determined on fins of goldfish mixed with each of three different species based on their level of host competence, including Prussian carp, Carassius gibelio (low competence), grass carp, Ctenopharyngodon idellus (non-competent), swordtail, Xiphophorus helleri (non-competent), and the four species combined. Compared with mean abundance (85.8 ± 25.1) on goldfish in the control group, the mean abundance on goldfish decreased significantly when paired with 10 Prussian carp (30.0 ± 16.5), but did not differ significantly when paired with 10 swordtail (70.0 ± 22.2), 10 grass carp (116.1 ± 33.2), or the multi-species of three Prussian carp, four grass carp and three swordtail (75.9 ± 30.8) during the 11-day experiment. The parasite was also found on the Prussian carp in the Prussian carp group and the multi-species group at a mean abundance of 7.1 and 10.9, respectively. Video recording showed that the school of goldfish mixed well with the Prussian carp, while they maintained separation from the grass carp and swordtail when mixed together. The distance between goldfish increased, and swimming speed and contact time decreased with the additional of other fish species for all groups. The results suggested that the presence of a low-competence host in sufficient numbers was a necessary condition for a dilution effect due to encounter reduction, and the dilution effect may also be enhanced by changes in schooling behavior of goldfish in the presence of low competence hosts. However, the presence of non-competent hosts did not result in any dilution effect owing to the specialist nature of the parasites and the lack of mixing with schools of goldfish.