School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, NSW, 2650, Australia.
Graham Centre for Agricultural Innovation, Charles Sturt University, Wagga Wagga, NSW, 2650, Australia.
Parasitol Res. 2021 Feb;120(2):515-523. doi: 10.1007/s00436-020-07021-7. Epub 2021 Jan 6.
This study aimed to investigate the links between parasites and behavioural traits of juvenile Murray cod (Maccullochella peelii). The Murray cod is an endangered Australian freshwater fish for which restocking programs are in place and there is a growing human consumption market. However, little is known about the parasites of these fish and how these parasites influence their behaviour and survival. Fingerlings and yearling fish were sourced from a hatchery and the wild, and after acclimatisation in the laboratory, variation in behavioural traits was examined using emergence, exploration and predator inspection tests. The fish were then euthanised to determine their age and examined for infection with parasites. Wild fish had more camallanid nematodes and lernaeid copepods than hatchery fish. An information theoretic approach using Akaike's Information Criterion (AIC) indicated that infection with protozoan cysts was an important factor for predicting the latency to emerge and explore a new environment, which was interpreted as reduced "boldness". In contrast, the presence of lernaeid copepods was included in two of the four best models predicting predator inspection, indicating that infected fish were less likely to inspect a predator. Source of fish (wild or hatchery) was found to be a strong influence on behavioural responses in all our tests. All parasites found in the present study are known to result in clinical signs of diseases in their fish hosts, raising the possibility that responses in tests of behavioural traits reflect side effects of infection. Additionally, the effect of host adaptation to not show signs of parasite infection, or more simply that the effects on behaviour are subtle and difficult to reveal with small sample sizes, is discussed. Nonetheless, we propose that it is important that infection with parasites is considered in fish behavioural studies both to assess survival behaviour and to avoid misinterpretation of behavioural tests of animal personality.
本研究旨在探讨寄生虫与幼年麦卡卢鳗鳕鱼（Maccullochella peelii）行为特征之间的联系。麦卡卢鳗鳕鱼是一种濒危的澳大利亚淡水鱼，目前正在进行再引进计划，并且人类对其的消费需求也在不断增长。然而，人们对这些鱼类的寄生虫知之甚少，也不清楚这些寄生虫如何影响它们的行为和生存。本研究从孵化场和野外采集了鱼苗和幼鱼，在实验室适应环境后，使用出洞、探索和检查捕食者测试来检查行为特征的变化。然后将鱼安乐死以确定其年龄，并检查其寄生虫感染情况。野生鱼比孵化场的鱼感染更多的 Camallanid 线虫和 Lernaeid 桡足类。使用 Akaike 信息准则（AIC）的信息论方法表明，原生动物包囊感染是预测潜伏期出洞和探索新环境的重要因素，这可以解释为“大胆度”降低。相比之下，桡足类的存在被纳入了四个最佳模型中的两个，用于预测检查捕食者的行为，这表明感染的鱼不太可能检查捕食者。在我们的所有测试中，都发现鱼类来源（野生或孵化场）对行为反应有很大影响。本研究中发现的所有寄生虫都已知会导致鱼类宿主出现疾病的临床症状，这增加了行为特征测试中的反应反映感染副作用的可能性。此外，还讨论了宿主适应不表现出寄生虫感染迹象的影响，或者更简单地说，行为的影响是微妙的，并且由于样本量小而难以揭示。尽管如此，我们还是建议在鱼类行为研究中考虑寄生虫感染，以评估生存行为，并避免对动物个性的行为测试产生误解。
