title: An acanthocephalan parasite increases the salinity tolerance of the freshwater amphipod Gammarus roeseli (Crustacea: Gammaridae).
abstract: Studies of the influence of parasites on host fitness generally conclude that parasites have a strong negative effect on their hosts. In this study, we have investigated experimentally the role of Polymorphus minutus, an acanthocephalan parasite, on the salinity tolerance of the freshwater amphipod Gammarus roeseli, one of its intermediate hosts. Unexpectedly, P. minutus-infected gammarids were more tolerant to salinity stress than uninfected ones. The mean lethal salt concentrations for 50% mortality of hosts tested were 17.3 (infected) and 9.7 g/L (uninfected). The parasitic load (one or two parasites per host) did not affect the result. The size of hosts had no significant influence on the salinity tolerance of either infected or uninfected gammarids. The mobility of all types of gammarid decreased when the salinity exceeded 9.0 g/L, but there was no significant difference between infected and uninfected gammarids. We discuss the higher salinity tolerance of infected amphipods in relation to O(2) consumption and osmoregulation. Finally, we demonstrate that the salinity tolerance is enhanced in the parasitized amphipod but without a significant change in behavior or an osmoregulatory adjustment.
authors.affiliation: Centre National de la Recherche Scientifique-Unité Mixte de Recherche (UMR 6553), Ecosystème Biodiversité et Evolution, Université de Rennes 1-Campus Beaulieu, 263 Avenue du Général Leclerc, 35042,, Rennes Cedex, France. christophe.piscart@univ-rennes1.fr
authors.forename: Christophe
authors.initials: C
authors.lastname: Piscart
authors.forename: Dennis
authors.initials: D
authors.lastname: Webb
authors.forename: Jean Nicolas
authors.initials: JN
authors.lastname: Beisel
mesh_terms: D000049:Acanthocephala / Q000201:enzymology / Q000472:pathogenicity*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D003445:Crustacea / Q000469:parasitology*; D004361:Drug Tolerance; D005618:Fresh Water; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D012965:Sodium Chloride; D000251:Adenosine Triphosphatases