Hostname: page-component-7c8c6479df-8mjnm Total loading time: 0 Render date: 2024-03-28T10:50:11.426Z Has data issue: false hasContentIssue false

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

Published online by Cambridge University Press:  01 June 2000

F. CEZILLY
Affiliation:
Laboratoire Ecologie-Evolution (UMR CNRS 5561 Biogéosciences), Université de Bourgogne, 6 blvd Gabriel, 21000 Dijon, France
A. GREGOIRE
Affiliation:
Laboratoire Ecologie-Evolution (UMR CNRS 5561 Biogéosciences), Université de Bourgogne, 6 blvd Gabriel, 21000 Dijon, France
A. BERTIN
Affiliation:
Laboratoire Ecologie-Evolution (UMR CNRS 5561 Biogéosciences), Université de Bourgogne, 6 blvd Gabriel, 21000 Dijon, France

Abstract

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.

Type
Research Article
Copyright
2000 Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)