Recent studies have shown the presence of large amounts of microRNAs (miRNAs; miRs) from damaged cells in the peripheral blood. In this study, we investigated the levels of miRNAs circulating in the blood plasma of whitefish (Coregonus lavaretus) after exposure to microcystin-LR. We used real-time PCR to examine the relative expression of plasma levels of 4 miRNAs (miR-122-5p and let-7c-5p, the liver-enriched microRNAs, miR-148a-3p which promotes the hapatospecific phenotype in mammals, and miR-92a-3p, a cell proliferation and angiogenesis promoter, potentially hepatocarcinogenic) during the first 48 h after exposure to MC-LR. We observed a rapid increase of miR-122-5p levels 8 h after exposure (P < 0.05), which continued to the end of the experiment. Our results demonstrated that the plasma miR-122-5p was indicative of MC-LR-induced liver injury, exhibiting areas under the curve close to 1 in ROC analysis (AUC = 0.976, P < 0.001). Although plasma levels of miR-148a-3p and miR-92a-3p were significantly elevated by the end of the experiment, their discriminative power was lower than reported for the miR-122-5p. Based on these results and reports on miRNA-based diagnosis of liver injuries in mammals, plasma miR-122-5p could be considered as a robust, new generation diagnostic biomarker in fish, helpful for the non-invasive diagnosis of liver damage.

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meiotic gynogenetic development of the rainbow trout (Oncorhynchus mykiss, walbaum 1792) was induced in the course of egg activation performed by the UV-irradiated homologous and heterologous (european grayling Thymallus thymallus linnaeus, 1758) spermatozoa. to recover diploidy in the gynogenetic zygotes, activated eggs were subjected to the high pressure shock in order to inhibit extrusion of the second polar body. gynogenetic rainbow trout progeny hatched from the eggs activated by the irradiated rainbow trout and grayling milt with similar hatching rates of 28.19% and 29.22%, respectively. however, gynogenetic rainbow trout produced with grayling semen had shown lower survival than gynogenotes provided with the homologous spermatozoa during two years of rearing. Viable hybrids are not produced between rainbow trout and grayling which ensured that fish obtained in this experiment were true gynogenetic progenies. A Robertsonian polymorphism characteristic for the rainbow trout from the studied strain was also observed among the gynogenetic specimens that exhibited diploid chromosome number ranging from 58 to 62 and stable chromosome arm number (fn= 104). no radiation-induced fragments of the paternal chromosomes were observed in the gynogenetic individuals. fish produced in both experimental variants were genotypic (XX) and phenotypic (gonads) females. The results confirmed that the gynogenetic protocol used in the present research is an efficient means of producing all-female gynogenetic rainbow trout stocks.

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