Which is the major trigger in aquatic environment for pearl oyster Pinctada fucata martensii sperm from gonad: Ammonia ion or pH?

To understand the roles of ammonia ion, pH, and salinity triggering sperm motility, effect of various ammonia ion concentrations (0, 1, 2, 3, 5, 10, 20 mM), external pH (pH_e, 7.00, 8.20, 9.00, 9.50) and salinity (20, 25, 31, 35, 40 psμ) on total motile sperm (TM) and swimming movement characteristics (curvilinear velocity - VCL, straight-line velocity - VSL, average path velocity - VAP, beat-cross frequency -BCF) were investigated for Chinese pearl oyster Pinctada fucata martensii, under laboratory condition. The TM and swimming movement characteristics were analyzed by a computer assisted sperm analysis system, based on sperm parameters of invertebrate. Ammonium ion as the major factor in triggering sperm motility, rather than pH_e was proved. Sperm motility was less affected by differing salinity solution without ammonium ion. Seawater containing 2 mM or 3 mM ammonium ion were suggested to be used for motility trigged and movement evolution for P. fucata martensii. The results in the present study are instructive for artificial external fertilization, gamete stocks and management in P. fucata martensii.