Sperm motility percentages and kinematics of Mytilus galloprovincialis (Lamarck, 1819) sperm exposed to different osmotic regimes and conditions: applications

The present study focused on characterising the sperm motility pattern in Mytilus galloprovincialis, among the most economically and ecologically important bivalve molluscs in European coastal areas, as a key step in developing sperm management protocols. To this aim, computer-assessed sperm motility parameters were evaluated as a function of time after activation and post-collection storage. In addition, the effect of combined low osmolality and pH on sperm motility was evaluated for the formulation of diluents capable of inhibiting sperm motility. Sperm motility parameters remained completely unchanged up to 60–80 min after activation, also when semen was activated after 6 h of cold incubation. All hypoosmotic solutions tested (100 to 600 mOsm) inhibited sperm motility, which could only be restored in the 600-mOsm inhibited samples, irrespective of the pH of the diluent. The ease of handling and long-lasting motility properties demonstrated by M. galloprovincialis spermatozoa may facilitate the application of technologies used in both hatcheries and laboratory research. In addition, the simply formulated diluent DI600 (2% NaCl, pH 7.7) can be considered a promising medium for the formulation of cryoprotective extenders or diluents for post-collection semen management.