The seasonal changes in immunocompetence and condition status in chub (Leuciscus cephalus): the potential associations to the metazoan parasites.
|Year of publication||2007|
|Type||Appeared in Conference without Proceedings|
|MU Faculty or unit|
|Description||The role of immune function is recently widely investigated in the context of trade-off between the different life-history traits. One of the main presumptions of the present study is that host immune system is exposed to the variety of parasites species, therefore hosts must develop efficient immune response to reduce the fitness cost due to parasitism. Therefore, we hypothesized and tested the potential associations between fish immunocompetence and infection by metazoan parasites. We performed the analyses of the seasonal changes in the selected physiological parameters and immunocompetence. and Moreover, the parasite presence and abundance was studied including four periods (spring, early summer, late summer and autumn) in 2004. A total of 83 chub (Leuciscus cephalus), a cyprinid fish species, were collected from one locality of Svitava River (South Moravia). The selected physiological and immune parameters were measured and the fish were investigated for the presence of metazoan parasites (Monogenea, Crustacea, Mollusca, Hirudinea, Digenea, Cestoda, Acanthocephala and Nematoda). Monogenea were the group with the highest prevalence and mean abundance and Digenea were found as the next group with high abundance values.. The parasite diversity and the infection parameters were highest in spring and early summer. When comparing parasite abundance in infra-communities among the periods investigated, the statistically significant highest values were observed in April and June for Monogenea, in April and November for Acanthocephala and in April for Cestoda. No differences in gender were recognized for immune parameters. The significant differences in spleen-somatic index were found among fish samples of different seasonal samples indicating higher investment in spleen size in April (after winterizing) and August (post-breeding with low GSI). The significant seasonal differences in erythrocyte and leukocyte cell counts, as well as in phagocyte count affecting respiratory burst, were also recorded. The analyses of differential leukocyte counts demonstrated only small seasonal variance in the composition of white blood cell components. The number of lymphocytes reached similar proportions in all periods investigated. However, the more obvious seasonal differences were observed in proportion of the developmental stages of neutrophilic granulocytes. The positive correlations between GSI and the parasite abundance of groups with higher infection parameters were found in males. Moreover, the positive association between Monogenea as the dominant parasite group and respiratory burst was observed. The higher investment in condition and the seasonal variation in GSI were associated with a decrease in immune function measured by spleen size or leukocyte cell count especially for males suggesting the seasonal energy allocation between immune function and somatic or reproductive investment.|