Sperm lipid peroxidation is correlated with differences in sperm quality during the reproductive season in precocious European sea bass (Dicentrarchus labrax) males

Precocious maturation is a common feature in European sea bass males which occurs just before reaching the marketable size, reducing growth and feed conversion and representing an important problem that reduces the commercial value of fish. The sperm produced by precocious sea bass males could be useful for reproductive purposes since these males could be selected for breeders and used earlier as a new broodstock. However the characterization of sperm quality in these males during the reproductive season is fundamental in determining its possible use in reproduction or cryopreservation. Thus, in the present work, sperm from precocious European sea bass (Dicentrarchus labrax) males was characterized to determine the effect of seasonality on parameters influencing quality throughout the reproductive period. Several characteristics associated with sperm quality were determined: motility, cell concentration, sperm pH and osmolality, cell viability, lipid peroxidation (malondialdehyde-MDA), phospholipid, cholesterol and fatty acid composition of the plasma membrane. The results demonstrated seasonal variation in some of the parameters tested, the quality of samples being relatively poor at the beginning of the spawning season, corresponding with the highest content of MDA and the lowest motility parameters. Cell viability, phosphatidylcholine and phosphatidylethanolamine, polyunsaturated fatty acids n−3 and saturated fatty acids did not show significant differences during the reproductive period. However, monounsaturated fatty acids and polyunsaturated fatty acids n−6 showed a reduction at the end of the reproductive period. Parameter correlations showed that motility was negatively correlated with lipid peroxidation (−0.394, p<0.05), cholesterol/phospholipid ratio (−0.449, p<0.05) and osmolality (−0.478, p<0.01). Our results demonstrated that lipid peroxidation could explain the seasonal variation in sperm quality, since the highest malondialdehyde value quantified in November is the only parameter associated with the lowest motility recorded at the beginning of the season. Thus, approaches to reduce lipid peroxidation as a consequence of oxidative stress could be useful for improving sperm quality in precocious sea bass males. The parameters quantified are consistent with the interpretation that January is the optimal month in the spawning season to collect sperm from precocious sea bass males for further reproductive purposes.