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Heritability estimates with a microsatellite parentage assignment based pedigree are of special interest in common carp cultured under traditional pond conditions. This method reduces common environment effects as all families can be grown immediately after hatching mixed in the same pond. We applied this method to study genetics of growth and processing traits in common carp at market size (1.5 kg and more). The experimental progeny was established by crossing 147 two-year old males and 8 females (six to eight-year old) of Hungarian synthetic mirror carp population. The fish grew up through three vegetation seasons and at the end a sample of 331 fish was examined for biometrical traits (standard length, body weight, relative head length, relative body height, relative body width), percent fat and processing traits (% processed body, % fillets with skin, % fillets without skin). It was shown that sex had a significant effect on most traits: females were larger and fatter than males, and they had both higher percent processed body and percent fillet with skin. Standard length, body weight, percent fat and relative head length had a high heritability (N0.5), while relative body height, relative body width, percent processed body and fillet yields had a medium heritability (0.2-0.5). We found relatively high positive genetic correlations between body size (standard length and body weight) and percent fat (0.71 and 0.59, respectively), favourable genetic correlations between body size and percent processed body (0.69 for standard length and 0.74 for body weight) and between body size and fillet yields (0.50-0.77). Genetic correlations between body size and body shape (relative head length, relative body height and relative body width) were weak to moderate, thus selection for better growth should have little impact towards more rotund shape. Relative head length had strong negative correlation (−0.7 to −0.9) with percent fat, percent processed body and percent fillet yields. This means that indirect selection for reduced relative head length should be effective in improving of fillet yield.

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Cryopreservation causes osmotic changes and oxidative damage that have sublethal and lethal effects on spermatozoa. We examined these osmotic and oxidative effects on common carp spermatozoa motility; membrane integrity; levels of thiobarbituric-acid-reactive substance (TBARS) and carbonyl groups (CP); and the activity of superoxide dismutase (SOD), glutathione reductase, and glutathione peroxidase (GPx). Sperm was diluted in dimethyl sulfoxide (DMSO) and ethylene glycol-based extenders, followed by equilibration, freezing, and thawing. Equilibration in DMSO extender resulted in a significant reduction of spermatozoa motility, but motility was induced in those spermatozoa following dilution with saline buffer, which usually inhibits undiluted spermatozoa motility. Spermatozoa velocity and membrane integrity decreased with both extenders following freezing and thawing. No significant difference in levels of TBARS or CP, or in SOD activity, was seen in samples equilibrated with either extender. The freeze/thaw process induced significantly higher levels of TBARS, CP, and GPx activity, but did not affect the level of SOD. Glutathione reductase activity was inhibited in samples exposed to DMSO extender. Ethylene glycol should be considered a preferred cryoprotective agent for common carp spermatozoa to reduce osmotic and oxidative stress during cryopreservation.

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Background information. Available data concerning the sperm morphology of teleost fishes demonstrate wide variation. In the present study, the spermatozoa of Siberian sturgeon (Acipenser baerii Brandt, 1869), a chondrostean fish, was investigated. In contrast with teleost fish, chondrostean spermatozoa have a head with a distinct acrosome, whereas other structures, such as a midpiece and a single flagellum, are present in spermatozoa of most species.Results. The average length of the head including the acrosome and the midpiece was 7.01 + − 0.83 µm. Ten posterolateral projections derived from the acrosome were present on a subacrosomal region, with mean lengths of 0.94 + − 0.15 µm and widths of 0.93 + − 0.11 µm. The nucleus consisted of electrodense homogeneous nuclear chromatin. Three intertwining endonuclear canals, bound by membranes, traversed the nucleus longitudinally from the acrosomal end to the basal nuclear fossa region. There were between three and six mitochondria, two types of centrioles (proximal and distal) in the midpiece and two vacuoles composed of lipid droplets. The flagellum (44.75 + − 4.93 µm in length), originating from the centriolar apparatus, had a typical 9 + 2 eukaryotic flagellar organization. In addition, there was an extracellular cytoplasm canal between the cytoplasmic sheath and the flagellum. Conclusions.A principal components analysis explained the individual morphological variation fairly well. Of the total accumulated variance, 41.45% was accounted for by parameters related to the head and midpiece of the sperm and the length of the flagellum. Comparing the present study with previous studies of morphology of sturgeon spermatozoa, there were large inter-or intra-specific differences that could be valuable taxonomically.

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