Fine structure of spermatozoa of three Sparid fish: common pandora, Pagellus erythrinus, gilthead seabream, Sparus aurata and blackspot seabream, Pagellus bogaraveo.

This study investigates the fine sperm structure of Sparids Pagellus erythrinus, Sparus aurata and Pagellus bogaraveo. Spermatozoa are differentiated into an acrosomeless head, a short midpiece and a long tail. The head is spherical in P. erythrinus and S. aurata but ovoidal in P. bogaraveo. In all species the nucleus reveals a deep invagination, in which the centriolar complex is located, and a satellite nuclear notch shaped like a club in P. erythrinus and P. bogaraveo and like a bell in S. aurata. Inside the nuclear notch occurs some electron-dense material in S. aurata is visible a cross-striated cylindrical body. The two centrioles show a "9+0" pattern and are oriented perpendicularly to each other in S. aurata and P. bogaraveo but not in P. erythrinus. The centrioles are linked to each other, as well as to the nuclear envelope, by electron-dense material. The distal centriole is linked to the nuclear envelope by means of a lateral plate and radial fibres in S. aurata and by means of basal feet, radial fibres and necklace in P. bogaraveo. In all species the midpiece houses one mitochondrion. The flagellum contains the "9+2" axoneme, is perpendicularly to the nucleus and shows an unpaired fin in P. erythrinus but none in S. aurata and P. bogaraveo. Knowledges obtained on sperm morphology may be an useful tool in aquaculture providing important references for evaluation of possible cell damages consequent to either cryopreservation procedures or exposure to contaminants.