Parasites of freshwater fish: evolutionary and ecological studies
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| Year of publication | 2017 |
| Type | Conference abstract |
| MU Faculty or unit | |
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| Description | Several ecological and evolutionary aspects of parasite communities of freshwater fish were studied. First, the potential risk of parasite transmission associated with cichlid introduction from Africa to Madagascar was studied. The communities of metazoan parasites in seven following cichlid species endemic to Madagascar were investigated in the selected localities of North and central parts of Madagascar: Paratilapia lamena, Paratilapia sp. 1, Paratilapia sp. 2, Ptychochromis grandidieri, Ptychochromis sp. 1, Ptychochromis sp. 2 and Paretroplus polyactis. In the same localities four cichlid species introduced from Africa to Madagascar were also identified and examined for parasites: Oreochromis niloticus, O. mossambicus, Coptodon rendalli. Our study revealed rare presence of endemic Malagasy cichlids. Introduction of African cichlids was linked with introduction of their metazoan parasites indicating parasite spillover. Our study revealed the Introduction of some highly invasive parasite species which represents a potential risk for endemic cichlids. Malagasy cichlids were found as competent hosts for specific monogeneans of African cichlids (Cichlidogyrus and Scutogyrus) but monogeneans of Malagasy cichlids (Insulacleidus) were strictly specific to their original hosts. We suggest that the source and time of introduction seems to represent the factor determining the local cichlid fauna in Malagasy cichlids. Second, the metazoan parasite communities of cyprinid fish species were studied in the Mediterranean area. High level of endemism was documented for host specific monogeneans. Dactylogyrus parasites were applied as the potential tool to investigate historical biogeographical contacts among cyprinid fish species of South Mediterranean Europe (Iberian Peninsula) and Northwest Africa. We showed that Dactylogyrus of Iberian Luciobarbus (Barbini, Cyprininae) were included in two phylogenetic lineages of Dactylogyrus. The similar pattern was observed for Cyprininae distributed in Northwest Africa. Our results indicated two historical contacts between Iberian and Northwest African Cyprininae associated with host switches of Dactylogyrus. We suggest that there are two historical ways of Dactylogyrus dispersion – north way from European Leuciscinae that likely originated in Siberia and dispersed from North to South Europe and south way from Asian Cyprininae to Africa and then to the Iberian Peninsula. Next, the extensive review of current knowledge on the major histocompatibility complex (MHC) in fish, specifically focusing on the MHC IIB class in cyprinid species was prepared. The general hypotheses on the origin of MHC genes and the mechanisms maintaining the polymorphism of these genes were presented and exemplified by studies performed on fish. Parasite-mediated selection (balancing selection) and reproductive mechanisms based on mating preferences were the most often cited mechanisms maintaining the extensive MHC polymorphism in fish. MHC polymorphism in fish populations is driven by parasites through overdominant selection or frequencydependent selection. However, the intermediate number of MHC alleles was documented at the individual level associated with the lowest parasite load. A trade-off between investing in MHC and other components of life maintenance has been hypothesized and documented by comparative analyses and within-species studies. Sexual selection is the main actor affecting the evolution of MHC polymorphism. Good or compatible genes of the males are generally selected by the females by mating choice. A mating preference for MHC genes has been documented in several fish species. It was proposed that the MHC diversity of the potential mating partner is evaluated by the olfactory system. |
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