Computer assisted sperm analysis (CASA) was used to characterize the motility of sea bass Dicentrarchus labrax spermatozoa and to study the effect of several physicochemical variables and heavy metals on sperm swimming performance. Duration of sperm motility in sea bass was very short ( 2+ and Pb 2+ , did not affect sperm motility when the activating media contained up to 100 ppm of the metal salts. In contrast, Hg 2+ modified...

The spermatozoa of Thunnus thynnus and Euthynnus alletteratus consist of an acrosome‐less head (comprising the ovoid nucleus and the short midpiece) and a long flagellar tail that contains the conventional 9 + 2 axoneme and lacks lateral fins. The centrioles are arranged at approximately right angles and lie outside of a shallow nuclear groove. The flagellum inserts laterally on the nucleus, therefore the spermatozoon is asymm...

The ovarian mass and gonadosomatic index (I G ) of bluefin tuna Thunnus thynnus , caught in the Strait of Gibraltar (Barbate) during migration to Mediterranean spawning grounds, were several times lower than those found in bluefin tuna from Mediterranean spawning grounds (Balearic Islands). Some of the bluefin tuna from Barbate (8.3%) were classified as immature (the most advanced oocytes present in the ovaries were early vite...