Infection with a trematode parasite differentially alters competitive interactions and antipredator behaviour in native and invasive crayfish

Abstract

Summary Parasites can have profound effects on host behaviour and species interactions, but the consequences of these impacts are inadequately understood. Three common crayfish in northern Wisconsin and Michigan (native Orconectes virilis, non‐native O. propinquus and non‐native and invasive O. rusticus) are intermediate hosts for trematode parasites, Microphallus spp. Some species in the genus Microphallus alter host behaviour, increasing their predation risk, but the effects of microphallids on crayfish are unknown. Orconectes propinquus replaces O. virilis in most lakes where they are introduced, and O. rusticus replaces both. These species replacements have major effects on macrophytes, macroinvertebrates and fish. Therefore, differential parasite impacts on crayfish could have community‐level effects if competitive outcomes are altered. We examined the shelter affinity of infected and uninfected individuals of all three species in laboratory experiments in the presence and absence of a conspecific. We also observed behaviour during agonistic interactions, and measured boldness by quantifying how quickly crayfish emerged from shelter with a predatory fish present. Infection with Microphallus substantially altered crayfish shelter affinity, shelter competition and boldness, though infection affected each species differently. Infection reduced shelter affinity in O. propinquus and the ability of O. virilis to compete for shelter against uninfected conspecifics. Infected crayfish were bolder in the presence of a predatory fish. Our results suggest that infection with Microphallus alters crayfish behaviour so that all three species are more vulnerable to predation. Orconectes propinquus is likely to suffer the greatest increase in predation when infected, due to a reduced affinity for shelter coupled with increased boldness. In lakes where crayfish species coexist, O. rusticus will probably be less affected by the parasite than either congener. Therefore, crayfish parasites could alter crayfish abundance and species composition in north temperate lakes via behavioural modifications.

Parasites alter freshwater communities in mesocosms by modifying invasive crayfish behavior

“…Previous research suggests that Microphallus presence is important for crayfish behavior but infection intensity is not (Reisinger et al. ), but future studies should test behavior over a wider range of intensities to verify this conclusion.…”

“…), are also bolder when infected with Microphallus (Reisinger et al. ). Therefore, while we cannot rule out the possible influence of collection lakes on our results, the differences we observed are most likely due to parasitism.…”

“…Therefore, the infection intensity in the crayfish included in this study (32 ± 4 parasites [mean ± SE]) is common and low compared to other sites. Previous research suggests that Microphallus presence is important for crayfish behavior but infection intensity is not (Reisinger et al 2015), but future studies should test behavior over a wider range of intensities to verify this conclusion.…”

“…In laboratory experiments, infected O. rusticus were bolder (emerged more quickly from shelter) than uninfected O. rusticus in aquaria containing predatory fish (Reisinger et al. ). These changes in behavior are likely to alter the impact of O. rusticus on lake communities.…”

Differential impacts of shared parasites on fitness components among competing hosts

“…Changes in host behavior, even subtle, can in turn have community‐wide repercussions (Lefèvre et al., ; Poulin, ; Thomas et al., ). Behavioral modification can include changes in activity levels (Kunz & Pung, ; Leung & Poulin, ; Webster, ), position in the water column (Hansen & Poulin, ; Rauque et al., ), aggression (Mikheev, Pasternak, Taskinen, & Valtonen, ), boldness (Reisinger, Petersen, Hing, Davila, & Lodge, ), and photophilia (Bauer, Trouvé, Grégoire, Bollache, & Cézilly, ; Rauque et al., ). Alterations of host behavior may lead to increased vulnerability to predation (Kunz & Pung, ) and reduced ability to compete for resources (Mikheev et al., ; Reisinger et al., ).…”