Parasite infection reduces predation risk by dragonfly larvae in crustacean prey
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Parasites can modify the phenotype of their hosts, altering host vulnerability to predation. Trophically-transmitted parasites often use host manipulation to increase their probability of transmission to the next host or reduce their chances of being consumed by the wrong species. However, phenotypic changes may actually increase the host’s vulnerability to other predators that are ‘dead-ends’ for the parasite, reducing parasite fitness while potentially impacting host populations. The isopod Austridotea annectens serves as intermediate host to Maritrema poulini (trematode) and display behavioural changes when infected that may increase parasite transmission. We tested the role of parasite infection on predation risk of isopods by a dragonfly nymph, a ‘dead-end’ parasite host. Size-matched isopod pairs were exposed to nymphs and observed until one was captured; subsequently isopod parasite abundance was determined. Isopods with lower parasite abundance were significantly more likely to be caught. Several mechanisms may explain this; behavioural modification by the parasites may be altering isopod behaviour to avoid predation by dead-end hosts, or, alternatively, increased activity may allow heavily infected isopods to avoid predation by sit and wait predators. Assessing the effects of parasites on their host’s ability to avoid predation is crucial in understanding how parasites may affect ecosystem dynamics and structure.
KeywordsPredation Predator–prey interactions Parasite-mediation Dragonfly Isopods
Laboratory assistance was provided by T. Dann. Special thanks to B. Ruehle, C. Selbach, and R. Grunberg for comments and advice on earlier drafts of this manuscript. Financial support for this project was provided by the Department of Zoology, University of Otago. SG was supported by the Promos scholarship from the German Exchange Program (Deutscher Akademischer Austauschdienst, DAAD).
Financial support for this project was provided by the Department of Zoology, University of Otago. SG was supported by the Promos scholarship from the German Exchange Program (Deutscher Akademischer Austauschdienst, DAAD).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Research involving animal rights
All applicable institutional and national guidelines for the care and use of animals were followed.
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