SPERM FEATURES IN TURBOT (SCOPHTHALMUS-MAXIMUS) - A COMPARISON WITH OTHER FRESH-WATER AND MARINE FISH SPECIES

This paper presents some features of turbot sperm and compares them wi th data reported in the literature on other freshwater and marine fish . In captivity, turbot spermiation period lasts 6 months. When compare d to other fish species, turbot males are characterized by low values of maximum gonadosomatic index (0.6-0.8%) and are poor sperm producers in terms of volume (0.2-2.2 ml), concentration (0.7-11.0 x 10(9) sper matozoa/ml) and total sperm number released per stripping (0.2-12.0 x 10(9) spermatozoa). Compared to most freshwater species, the duration of cell movement is long (1-17 min). The spermatozoon of turbot can be considered to be of a primitive type. A very high protein content (8. 8 mg/ml) is found in the seminal fluid of turbot. Increasing collectio n frequency of turbot males, from monthly to fortnightly and weekly st ripping, results in the release of successive samples presenting decre asing semen volume and spermatozoa concentration. Similar spermatozoa concentration and total volume of semen produced per turbot, during a 2-month experimental period, are released from males submitted to an a nnual light and temperature cycle, compared to those receiving a 6 mon th contracted light and temperature schedule.