Sperm production and quality in brill Scophthalmus rhombus L.: relation to circulating sex steroid levels
The aims of the present study were to characterize sperm quality and to quantify seasonal changes in sexual hormone (testosterone [T], 11-ketotestosterone [11-KT] and 17,20β-dihydroxypregn-4-en-3-one [17,20β-P]) levels in male brill (Scophthalmus rhombus) plasma, as well as to test a more intensive sampling strategy to establish relationships between sex steroid levels and sperm production parameters. Sperm concentration ranged from 0.5 to 3.1 × 109 spermatozoa mL−1, and changes in sperm quality parameters depending on sampling date were observed. Plasma sexual steroid levels remained high and changed in parallel during the spawning season and afterwards decreased to very low levels in summer. The analysis of annual changes of 11-KT and T ratios suggests that 11-KT can be the main circulating androgen for stimulating spermatogenesis in S. rhombus and that T could be involved in the beginning of spermatogenesis through the positive feedback on brain-pituitary-gonad axis. Finally, daily 11-KT and T levels showed similar patterns of variation in males sampled, whereas 17,20β-P amounts showed somewhat opposite trends. These differences could be related with the different role of androgens and progestin during the spermatogenesis.
KeywordsMotility Sperm concentration Scophthalmus rhombus Sex steroids
This work has been founded by the project INIA TRT2006-00011-C02-01, “Establecimiento de una metodología de reproducción artificial para la obtención de puestas de calidad en el parracho (Scophthalmus rhombus). The authors thank J.M. López, J.M. Márquez, J. López and B. Sánchez from Agencia de Gestión Agraria y Pesquera de Andalucía. Thanks are also given to R. Osta at ICMAN for her assistance in steroid measurements.
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