CALCIUM AND CYCLIC-AMP MEDIATE SPERM ACTIVATION, BUT CA2-SAVIGNYI( ALONE CONTRIBUTES SPERM CHEMOTAXIS IN THE ASCIDIAN, CIONA)

Sperm-activating and -attracting factor (SAAF) released from the ascid ian, Ciona savignyi, was partially purified from egg seawater with eth anol extraction and separation with the two-phase system of chloroform and water. SAAF did not activate sperm motility and cAMP synthesis in calcium-free seawater (CaFSW), but activated the both in the presence of Ca2+. Sperm activation by SAAF in Ca2+-containing medium was inhib ited by flunarizine, a T-type Ca2+ channel antagonist, but L-type Ca2 channel specific antagonists had no effect. Theophylline, a phosphodi esterase inhibitor, induced the increase of cAMP level and sperm activ ation in CaFSW without SAAF. On the other hand, the theophylline-activ ated sperm in CaFSW did not exhibit chemotaxis toward the tip of glass capillary containing SAAF, but upon the addition of Ca2+ they were at tracted toward SAAF in the same manner as chemotaxis in normal artific ial seawater. These results suggest that sperm activation is induced b y the increased cAMP level caused by Ca2+ influx through T-type Ca2+ c hannel, and that Ca2+ alone mediates the sperm chemotaxis in Ciona.