Characterization of zebra mussel (Dreissena polymorpha) sperm motility: duration of movement, effects of cations, pH and gossypol

We have examined effects of time after activation, pH, sodium and potassium , and gossypol concentrations on sperm motility of zebra mussel (Dreissena polymorpha). Zebra mussel spermatozoa appeared to have remarkable viability in the fresh water in comparison with freshwater fish sperm. Duration of s perm motility in fresh water is possibly one of the longest among freshwate r animals, since it was not significantly changed 3 h after incubation at r oom temperature (20 degreesC) or 24 h of incubation at +/-0 degreesC. High osmotic pressure suppresses sperm motility and effects of sodium and potass ium are similar. Spermatozoa were inactive at acid pH and became gradually motile when exposed to pH 6.0-9.0. Gossypol appeared to be a very potent sp ermicidal agent and inhibited motility. This compound also inhibited fertil ization. We observed some differences in gossypol effects on spermatozoa be tween North American and European zebra mussels. These data on zebra mussel sperm biology may be useful for better handling of gametes under laborator y conditions.