The gills of Lake Victoria cichlids: theatre for parasite interspecific relationships¬ and niche segregation

Abstract

Hosts often harbour multiple parasite species, that may interact and thus modify each other’s effects on host fitness. These interspecific interactions between parasites may result in parasites occupying different niches within hosts (niche segregation). The within-host distribution of different parasite taxa may constitute an important axis of infection variation among host populations and species. We investigated the microhabitat distributions and species interactions of gill parasites infecting 14 sympatric Lake Victoria cichlid species. We found that the two most abundant parasite taxa (the monogenean Cichlidogyrus spp. and the copepod L. monodi) had non-random microhabitat distributions on gills, which also differed between host species. This may indicate microhabitat selection by the parasites and cryptic differences in the host-parasite interaction among host species. Relationships among parasite of different genera were synergistic: the abundances of Cichlidogyrus spp. and the copepods L. monodi and E. lamellifer tended to be positively correlated. In contrast, relationships among congeners (members of Cichlidogyrus belonging to different species) were antagonistic. Together with niche overlap, this suggests competition among species of Cichlidogyrus. These findings may indicate host species-specificity in parasite niche selection and consequently in the host-parasite relationship. Microhabitat distribution of parasites over gills may represent an important axis of infection variation, therefore we suggest to include the location of parasites on the host in future studies, alongside with canonical measures of infection (i.e. parasite abundance).