Parasite‐induced alterations of host behaviour in a riverine fish: the effects of glochidia on host dispersal

Abstract

Summary Parasitic species can affect host behaviour in various ways. Freshwater mussels of the superfamily Unionoidea have a glochidia larva that is parasitic on fish. Our aim was to evaluate whether fish exposed to glochidia have distinct behaviour that could affect the upstream dispersal of the parasite. Many freshwater mussels are highly endangered, and understanding the relationships with their hosts is important for their conservation. However, research on the behavioural effects of parasitism on fish host activity and/or the upstream dispersal of mussel larvae in nature has received little attention. Specifically, we examined a fish (the chub, Squalius cephalus) that hosts the larval stage of a freshwater bivalve (Anodonta anatina) and investigated alterations in host behaviour induced by the parasite. One laboratory and two field experiments were conducted using passive integrated transponder systems and radio‐telemetry. Infected fish were generally less active in the laboratory and, in the field, dispersed less far upstream. Moreover, radio‐telemetry revealed a habitat shift by the infected fish, which were found further from the riverbank. We suggest that behavioural changes in the fish that are induced by glochidia do not facilitate the long‐distance dispersal of the mussel but rather cause reductions in fish activity and slight habitat shifts. Possible consequences of such behavioural alterations are discussed.

Limited movement of freshwater mussel fish hosts in a southern US river

“…If fish hosts do not move far, most mussel propagules will be deposited within the mussel bed leading to localized, positive feedbacks between mussel density, fish hosts, and mussel recruitment. Infestation of European chub (Squalius cephalus) with duck mussel (Anodonta anatina) glochidia resulted in a reduction of the host's activity and movement, restricting mussel dispersal (Horký et al, 2014). Similar to our study, Terui et al (2014) found an overall upstream bias in movements of Masu Salmon (Oncorhynchus masou masou), the host of the Japanese freshwater pearl mussel (Margaritifera laevis), recapturing *70% of hosts near original capture locations.…”

“…Based on previous studies investigating the sinking and drift rates of juvenile mussels (Schwalb et al, 2010;Irmscher, 2014), we estimated that juveniles drift approximately 50-250 cm during summer low flow conditions in the Little River, which is within the same range of upstream movement of host fish that we measured. Studies of mussel-host relationships have frequently investigated luring strategies and other aspects of glochidia-host interactions that enhance recruitment (e.g., Sietman et al, 2012); however, upstream dispersal is an additional advantage that mussels gain from the relationship with their host (Mansur & da Silva, 1999;Barnhart et al, 2008;Horký et al, 2014). Our study of host fishes at four sites in one season is a snapshot in time and space.…”

“…The small proportion of fish hosts that move long distances should be of great importance for mussel dispersal (Horký et al, 2014). Mussel beds represent local subpopulations that are linked into a larger metapopulation through infrequent dispersal (Vaughn, 1993;Newton et al, 2008;Vaughn, 2012).…”

A “parasite-tag” approach reveals long-distance dispersal of the riverine mussel Margaritifera laevis by its host fish

“…Glochidia can affect movement activity and local habitat selection of host fish through triggering immune responses (Horky et al, 2014). Although we could not compare dispersal patterns between infected and non-infected fish, incorporating this aspect into sampling design might provide an informative and fruitful avenue for research.…”

Early life history and spatiotemporal changes in distribution of the rediscovered Suwannee moccasinshell Medionidus walkeri (Bivalvia: Unionidae)

“…Evaluating P. nigrofasciata behavior and movement patterns during the M. walkeri parasitic larval stage is useful to characterize the mussel's dispersal and recruitment capabilities (Schwalb et al 2011, Horký et al 2014, Jones et al 2015. P. nigrofasciata have been shown to be 'long-term residents' that generally live in small areas of about 30 m with only a few fish documented to move up to 420 m (Freeman 1995).…”