COMPARATIVE HOST-PARASITE RELATIONSHIP OF 2 COPEPOD SPECIES ECTOPARASITIC ON 3 FISH SPECIES

The dispersal patterns of two sea lice species (Lepeophtheirus thompso ni and L. europaensis) are analysed on their three Mediterranean teleo st hosts (turbot for L. thompsoni and brill and flounder for L. europa ensis). The influence of host age and ecology (marine for turbot and b rill and brackish waters for flounder) is studied as well as are the d ifferences in colonisation and diet strategies (blood for L. thompsoni and mucus for L. europaensis) displayed by these two copepod species. This study confirms the known differences in the degree of specialisa tion displayed by these two parasite species. It shows the influence o f abiotic factors in determining parasite loads and localisation withi n the host. The spectacular differences found between L. europaensis o n brill and on flounder show that the biotic factors (the host) have a considerable impact as well. Depending on the host-parasite pair invo lved and on the localisation of the parasite, differences are found co ncerning the impact on host population dynamics. We finally discuss th ese results in terms of plasticity, adaptation and divergence, in the light of previous work on the same or on closely related parasite spec ies.