Publication details

The analysis of the associations between variability of selected MHC genes and infection of metazoan parasites in Carassius auratus gibelio, the host with the pecular reproductive strategy.



Year of publication 2007
Type Appeared in Conference without Proceedings
MU Faculty or unit

Faculty of Science

Description Major histocompatibility complex genes (MHC) encoding posttranslational modified glycoproteins are localized on cell-surface, where they present antigen peptide to T lymphocytes and stimulate an immune response. The classical MHC molecules are assigned to two classes, MHC I and MHC II. The DAB genes (MHC IIB class) include two allelic lineages DAB1 and DAB3 in cyprinid fish species. The variability in DAB genes was studied in relation to the parasitism following the hypothesis of pathogen-driven selection which represents one of mechanism promoting MHC polymorphism. Carassius auratus gibelio (Cyprinidae) is a single species of vertebrates with coexistence of bisexual and gynogenetic reproduction. The individuals with different ploidy status co-occur in the natural populations. The aims of the present study were 1) to study the population structure of Carassius auratus gibelio and the structure of metazoan parasite communities in the summer 2005 and 2006, 2) to analyze the selected somatic, physiological parameters and MHC variability in the individuals differing in ploidy level and reproductive strategy, 3) to analyze the associations between MHC variability and infection of metazoan parasites, and finally 4) to estimate the importance of genetic variability MHC for invasive success of C. auratus gibelio. A total of 115 individuals from mixed population were used for the parasitological dissection. For each individual the sex and ploidy status were determined. Variability of exon 2 MHC IIB DAB genes was analyzed using molecular methods. In the natural population of C. auratus gibelio the trend to increase the number of diploid individuals and decline the number of triploid females was found when comparing to the population structure studied during last years. The abundance of metazoan parasites was higher in 2005 than in 2006 probably due to the flood in 2006. The high allelic diversity was recorded in the population studied; a total of 69 different alleles were recognized. Several individuals expressed DAB1 or DAB3 alleles; others expressed the alleles of both allelic lineages. The number of DAB alleles varies from one to six per individual. Diploids expressed one or two alleles in the majority of cases, whereas triploids expressed mainly three alleles. Triploids also expressed higher number of DAB3 alleles, whilst diploids expressed higher number of DAB1 alleles in 2006. The higher total number of alleles in triploids was connected with trend of higher parasite infection. The categories of fish being exposed to a wider range of macroparasites had more diverse their MHC class IIB genes. A negative relationship between condition factor and number of parasites or spleen somatic index in triploid females indicates that better somatic condition is connected with lower metazoan parasites load.
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