A. BERTIN

A. GREGOIRE

F. CEZILLY

When two parasite species are manipulators and have different definitive hosts, there is a potential for conflict between 
them. Selection may then exist for either avoiding hosts infected with conflicting parasites, or for hijacking, i.e. 
competitive processes to gain control of the intermediate host. The evidence for both phenomena depends largely on the 
study of the relative competitive abilities of parasites within their common intermediate host. We studied the effects of 
simultaneous infection by a fish acanthocephalan parasite, Pomphorhynchus laevis, and a bird acanthocephalan parasite, 
Polymorphus minutus, on the behaviour of their common intermediate host, the amphipod Gammarus pulex. We compared 
the reaction to light and vertical distribution of individuals infected with both parasites to those of individuals harbouring 
a single parasite species and uninfected ones under controlled conditions. Compared to uninfected gammarids that were 
photophobic and tended to remain at the bottom of the water column, P. laevis-infected gammarids were attracted to light, 
whereas P. minutus-infected individuals showed a modified vertical distribution and were swimming closer to the water 
surface. The effects of both P. laevis and P. minutus appeared to be dependent only on their presence, not on their intensity. 
Depending on the behavioural trait under study, however, the outcome of the antagonism between P. laevis and P. minutus 
differed. The vertical distribution of gammarids harbouring both parasites was half-way between those of P. laevis- and 
P. minutus-infected individuals, whereas P. laevis was able to induce altered reaction to light even in the presence 
of P. minutus. We discuss our results in relation to the occurrence of active avoidance or hijacking between conflicting 
manipulative parasites and provide some recommendations for future research.</jats:p

Crossref

Parasitology

Conflict between co-occurring manipulative parasites? 
An experimental study of the joint influence of 
two acanthocephalan parasites on the 
behaviour of <i>Gammarus pulex</i>

Conflict between co-occurring manipulative parasites? 
An experimental study of the joint influence of 
two acanthocephalan parasites on the 
behaviour of
                    Gammarus pulex

Conflict between co-occurring manipulative parasites? An experimental study of the joint influence of two acanthocephalan parasites on the behaviour of Gammarus pulex

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