EFFECT OF TEMPERATURE ON INTERACTION BETWEEN EGGS AND SPERMATOZOA OF SEA URCHIN

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Abstract
Fertilization in the sea urchin, Anthocidaris crassispina, showed marked temperature dependence; high temperatures (15°-30°C) were required for fertilization. In contrast, fertilization in Hemicentrotus pulcherrimus occurred over a wide range of temperatures (0°-30°C). The mechanism of this temperature effect in Anthocidaris was investigated. The number of sperm bound to the egg surface and the rate of the acrosome reaction were markedly reduced by lower temperatures (0°-10°C). Furthermore, an abnormal elongation of the sperm head tip occurred with higher frequency at lower temperatures. In contrast, the egg activation with calcium ionophore A23187 was not prevented at 10°C. The swimming activity measured by distance traveled was also relatively high at 0°C, although the activity increased as the temperature rose. These results strongly suggest that temperature exerts a direct influence on fertilization in Anthocidaris by acting on the acrosome reaction. The increased fertilization rate at higher temperatures in Anthocidaris corresponds to the higher temperature observed during the breeding season of this species.