Induction of maturation and spermiation in the male European eel: assessment of sperm quality throughout treatment

Abstract

Weekly injections of human chorionic gonadotropin (hCG; 1·5 IU g−1W) induced spermiation in 87–100% farmed male European eels Anguilla anguilla over a 10‐week period, producing 3 ml (100 g)−1 milt volume, at 1˙4×109 spermatozoa ml−1 sperm mobility peaked in ninth week of treatment with 97% of males with motile sperm. Gonadotropin‐treated males showed earlier but similar morphological changes to control males. Whereas higher sperm density was obtained 6 h after hCG administration, higher percentage of motile cells and longer sperm mobility were observed 24 h after the treatment indicating that this is the optimum time to obtain good sperm after the hormonal induction. Several monounsaturated fatty acids in sperm increased significantly from week 5 to 9 of treatment (when highest volume, density and mobility of milt were recorded), whereas eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and total n‐3 polyunsaturated fatty acids (PUFAs) were significantly reduced. Fatty acid levels returned to initial values after 13 weeks of treatment. These results are in agreement with the reduction of n‐3 PUFAs recently observed in the ovary of female Japanese eel during artificial maturation, and an attempt is made to suggest a physiological explanation of its possible relation with sperm quality.