A DILUENT FOR SPERM CRYOPRESERVATION OF GILTHEAD SEABREAM, SPARUS-AURATA

Sperm of gilthead seabream, Sparus aurata, was diluted with solutions of different osmolarities and pH. The effect of the different diluents on sperm motility (intensity and percentage of motile sperm) was studied. Motility was induced as early as 10 s after mixing the sperm with diluents having an osmotic pressure higher than 500 mOsm/l. The intensity of motility decreased when the osmotic pressure was reduced, and was zero or significantly inhibited when the osmotic pressure of the diluent (300-380 mOsm/l) was close to that of the fish's seminal plasma (364.6±3.03 mOsm/l). The pH of the diluent did not have any effect on sperm motility (in a range of 6.8 to 8.9). A diluent which prevents spermatozoa motility (osmotic pressure 375 mOsm/l and pH 7.35) was successfully used to cryopreserve S. aurata sperm at -196°C. This diluent is considered promising for the long-term preservation of gilthead seabream sperm. © 1990.