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Factors contributing to the coexistence of two reproductive forms of Carassius gibelio in the Czech Republic.

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Rok publikování 2018
Druh Konferenční abstrakty
Fakulta / Pracoviště MU

Přírodovědecká fakulta

Popis The first records of Carassius auratus gibelio species arose in 1976. Since 1990 the transformation from originally triploid (likely gynogenetic) towards the mixed diploid-polyploid population (with coexisting gynogenetic and sexual forms) was reported. This unique fish species, which originated from Asia, is characterized by high environmental tolerance and adaptability. Therefore, it is a perfect model of a successful, invasive species. However, until now, the potential differences in physiology, immunity and/or parasitic between two coexisting reproductive forms were not fully investigated. The aim of this study was to investigate the parasite load and the selected physiological and immune parameters in two reproductive forms of C. auratus gibelio. According to mtDNA analysis, C. gibelio, which is a target of our study, is the most common form of Carassius auratus complex in the Czech Republic. Apart from C. auratus gibelio there are also other three forms reported in Czech Republic in low frequency i.e. C. auratus auratus, C. auratus langsdorfii and C. auratus M-line. In the frame of our four-year study, 22 different species of metazoan parasites were found on 195 fish individuals investigated. Monogenea represented the most frequent group of parasites in both diploid likely sexual females and males, and triploid likely gynogenetic females. From all parasite species, 3 species of Monogenea, namely in Dactylogyrus dulkeiti, Dactylogyrus anchoratus and Gyrodactylus sprostonae were found in the high prevalence and the highest intensity of infection. This pattern was recognized in both reproduction forms. We also found that both sexual individuals and gynogenetic females were parasitized more in the last year in comparison with three previous years. We did not confirm the prediction of Red Queen hypothesis as we did not find significantly higher level of infection in gynogenetic females compared to sexual forms in any of four years studied. Concerning physiological parameters studied, we confirmed statistically higher erythrocyte count in diploid form when compared to triploid form. On the other hand, higher level of haematocrit was found in diploid males compared to both groups of females. From the immunity point of view, we did not observe any significant difference between reproductive forms of C. auratus gibelio. Nevertheless, difference in some physiological and immune parameters were found among the specimens collected in different years. Activity of oxidative burst reached significantly lower values in the last year of study for both forms. On the other hand, in the same year the activity of the complement was significantly higher when compared to other 3 years. Condition factor and gonado-somatic factor were lower in diploid males when compared to sexual and asexual females. We also reported higher value of spleen-somatic index (considered as an indicator of immunocompetence) of diploid males when compared to both females. Thus, it seems that the high investment in gonad development in both gynogenetic and sexual females is compensated by low investment in immunocompetence. This result may indicate that investment into traits related to the maintenance, reproduction and immunity are determined rather by sex than by different ploidy level likely related to different modes of reproduction (gynogenetic vs. sexual). This may contribute to the coexistence of two reproduction forms of C. gibelio living in the same environment.
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