EFFECT OF EXTENDER SOLUTIONS AND DILUTION ON MOTILITY AND FERTILIZINGABILITY OF EASTERN OYSTER SPERM

Optimization of conditions for short-term storage of gametes is import ant for the production of seedstock and genetic management of broodsto ck in aquaculture. We conducted a series of experiments to evaluate re frigerated storage of sperm of the Eastern oyster (Crassostrea viginic a). Our objectives were to: 1) compare motility of oyster sperm suspen ded in artificial seawater (ASW) at five osmotic pressures (22, 203, 4 03, 601, or 833 mOsm/kg) over 24 h; 2) compare motility of sperm suspe nded in solutions of ASW, Hanks' balanced salt solution (HBSS), or DCS B4 solution tall at 833 mOsm/kg) over 4 days of refrigerated storage; 3) compare motility of sperm suspended in ASW or HBSS (833 mOsm/kg) in six ratios of sperm:extender (1:0, 1:1, 1:3, 1.7, 1:15, or 1:31) over 4 days of refrigerated storage, and 4) compare motility and fertilizi ng capacity of oyster suspended in ASW (200 and 830 mOsm/kg), ASW with 6% glycine (ASW+G), HBSS, and calcium-free HBSS (C-F HBSS) tall at 83 0 mOsm/kg). Significant differences (p < 0.001) were found in the moti lity of sperm suspended in ASW of different osmotic pressures. No sign ificant differences (p = 0.267) were found in motility of sperm suspen ded in ASW, HBSS, or DCSB4. Significant differences (p < 0.001) were f ound in the motility of sperm suspended in different ratios of sperm:e xtender. The highest motility was found in undiluted sperm and the low est in the 1:31 dilution for sperm suspended in ASW or HBSS. Significa nt differences (p = 0.0001) were found in motility of sperm suspended in various extenders. The highest motility was found in sperm diluted in CF-HBSS (96%), and the lowest in sperm diluted in ASW at 200 mOsm/k g (12%). The highest percent fertilization (48%) las measured by larva l development at 12 h) was obtained when eggs were fertilized with spe rm diluted in C-F HBSS. These results indicate that for storage (4 day s), it is best to leave sperm samples undiluted. However, when sperm s amples are diluted for use within 24 h, it is best to maintain high sp erm concentrations and to use C-F HBSS as an extender.