Initiation of Sperm Motility in Ciona intestinalis by Calcium and Cyclic AMP(Developmental Biology)

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The motility of Ciona spermatozoa, which had been prevented by calcium chelating agent EGTA (0.125-1.0 mM), was initiated by the subsequent addition of calcium (0.5-1.0 mM). In addition, when high concentrations of EGTA (up to 32 mM) were added to other sperm suspensions in which spermatozoa were already moving vigorously, the motility continued. These findings suggest that while calcium is not indispensable to maintain sperm motility, it is an effective external factor in the initiation of sperm motility. Spermatozoa demembranated with Triton X-100 were motile in the reactivating medium in which CAMP presumably synthesized from ATP in the medium by the contamination of endogenous adenylate cyclase: This was thought to be associated with incompletely removed or solubilized sperm membrane residue. On the contrary, when demembranated sperm were suspended in reactivating medium containing phosphodiesterase in which the auto-synthesized CAMP would be converted back to 5'-AMP, axonemes were completely quiescent even in the presence of an energy source, MgATP^<2->. Subsequent addition of a considerable amount of CAMP to the phosphodiesterase-immotile sperm induced axonemal movement instantly, suggesting that exposure of axonemes to CAMP may be indispensable for the initiation of sperm motility in Ciona.
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