The role of MHC variability in fish immuncompetence, condition and parasite selection in fish males (Abramis brama L.)
| Title in English | The role of MHC variability in fish immuncompetence, condition and parasite selection in fish males (Abramis brama L.). |
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| Authors | |
| Year of publication | 2007 |
| Type | Appeared in Conference without Proceedings |
| MU Faculty or unit | |
| Citation | |
| Description | The highly polymorphic MHC (major histocompatibility complex) genes play a central role in controlling immunological self and non-self recognition, and they permit to recognize the foreign antigens derived from pathogens or parasites, especially throughout the peptide binding regions. Two hypotheses explaining the factors maintaining the extensive MHC polymorphism have been proposed: parasite or pathogen driven selection and on MHC-based mating preferences. The aim of this study was tested whether MHC diversity is related to the fish condition status, immunocompetence measured by a simple immunological parameter such as the spleen size and sexual ornamentation in male fish during the breeding period. Moreover, the potential associations between MHC variability and parasite infection and/or parasite diversity were hypothesized and tested. A total of 28 males of common bream (Abramis brama L.) were collected and investigated during the breeding period from one water reservoir (Dyje River, Czech Republic). The spleen size was used as a measure of immunocompetence. Condition factor reflecting a general condition status and sexual ornamentation (breeding tubercles) were recorded for each individual. Males were subjected to the parasite dissection (only metazoan parasites) and MHC analyses. Two groups of DAB alleles (MHC IIB class), DAB1 and DAB3, were recognized according to nucleotide and amino-acid similarities and both groups were well supported using the phylogenetic analyses. Male individuals expressed one or two alleles of the same group (DAB1 or DAB3 termed as single allelic type) or different allelic groups (DAB1 and DAB3 termed as combined allelic type). Several individuals shared identical alleles; however, the presence of parasite species was not associated with the presence of a particular allele. Moreover, the expression of different allelic groups (DAB1, DAB3 or both DAB1 and DAB3) in individuals was not associated with parasite presence or diversity. The nucleotide diversity in individuals expressing a single type of alleles (DAB1 or DAB3) increased with the abundance of ectoparasite species i.e. with Dactylogyrus spp. (Monogenea) and Ergasilus sp. (Crustacea). This suggests that the expression of two alleles of a single allelic type is connected with high metazoan parasite infection whilst no significant influence of parasitism on the combined allelic type was found. The higher diversity in MHC seems to be disadvantageous for fish male immunocompetence measured by spleen size. The condition factor was higher in fish expressing the combined allelic type, which suggests that the presence of alleles of different lineages in individuals seems to be advantageous for male vigour. The expression of a single allelic type was connected with higher sexual ornamentation, which could support the role of MHC in connection with hypothesis of sexual selection of “good genes”. |
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