THE LINKS BETWEEN MHC DIVERSITY, HOST CONDITION AND PARASITISM IN COMMON BREAM (ABRAMIS BRAMA)
| Authors | |
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| Year of publication | 2006 |
| Type | Article in Proceedings |
| Conference | 14th Helminthological Days, 8-12 May(2006), Ředkovec, Czech Republic |
| MU Faculty or unit | |
| Citation | |
| Field | Zoology |
| Keywords | MHC IIB diversity-metazoan parasites- host condition-cyprinid fish |
| Description | Following the hypotheses of parasite-driven selection and MHC-based mating preferences the patterns of MHC (major histocompatibility complex) diversity of class IIB genes were investigated in males of common bream collected in the spawning period. The potential associations of MHC diversity and (1) fish condition status, (2) immunocompetence measured by spleen size, (3) sexual ornamentation measured by the number of breeding tubercles, and (4) metazoan parasite diversity were tested. Two allelic groups DAB1 and DAB3 were recognized using the nucleotide similarity and phylogenic analyses. The individuals expressed the alleles of one or both allelic groups; thereafter the individuals were classified in three groups: (1) expressing one DAB1 allele, (2) expressing two alleles of single lineage (DAB1 or DAB3) and (3) expressing the combined type of alleles (DAB1 and DAB3). The Monogenea was the most common group of metazoan parasites with the genera Gyrodactylus and Dactylogyrus reaching the highest abundance. The Digenea and Nematoda were the most common groups of endoparasites; among them the following species reached the higher abundance: Diplostomum spp., Cotylurus pileatus and Contracaecum spp. The abundance of ectoparasites (Monogenea and Crustacea) was positively related with sexual ornamentation confirming the mechanism of Hamilton-Zuk hypothesis. The expression of the single allelic type (DAB1 or DAB3) was connected with higher sexual ornamentation when comparing with the individuals expressing a combined type of alleles (DAB1 and DAB3). The results support the role of MHC in the view of the hypothesis of sexual selection of “good genes”. The presence of any special DAB allele shared by the different individuals was not associated with parasite presence or diversity. The nucleotide diversity in individuals expressing a single type of alleles increased with the abundance of ectoparasitic Dactylogyrus spp. and Ergasilus sp. The level of nucleotide variability of the expressed alleles of a single allelic type was connected with decreased immunocompetence. However, the condition factor was higher in fish expressing the combined allelic type. The level of nucleotide diversity in the individuals expressing the alleles of combined type was not important for immunocompetence and parasitism. Those results suggest that a type of expressed alleles is an important key determining fish condition and level of parasitism when the combined type is favored before the single type. |
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