Effect of the aging process on the quality of sea bass (Dicentrarchus labrax) semen

At the end of the female spawning period, an aging phenomenon affects sea b ass spermatozoa. Compared with 24 days after the beginning of the female sp awning season, a significant decrease of spermatozoa concentration was asse ssed 14 days after the end of this period (from 2.88 +/- 0.08 to 2.44 +/- 0 .11 x 10(10) spermatozoa mL(-1)). Morphological studies revealed a detachme nt of the plasma membrane in the apical part of the cell, A cytoplasmic spa ce containing vacuoles appeared. A lower ATP content and adenylate energy c harge were also recorded (respectively: 86.5 +/- 4.5 versus 63.9 +/- 1.3 nm ol/10(9) spermatozoa and 90.2 +/- 1.2 versus 84.7 +/- 1.3%). Towards the en d of the reproductive period a lower motility index was determined at 30 s post-activation (2.7 +/- 0.2 versus 0.8 +/- 0.2). Furthermore, the fertiliz ing capacity of sperm samples collected at the beginning of the milting sea son (49.9 +/- 2.6%) was significantly higher than that assessed at the end of this period (31.5 +/- 0.9%) and the short-term storage and freezing capa cities were also altered. The existence of sperm senescence in sea bass is discussed in relation with the discontinuous spermatogenesis suggested in t his fish species.