REPRODUCTIVE CYCLE IN CYPRINA ISLANDICA

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Abstract
In Cyprina (Arctica) islandica, living in deep water off Point Judith, R. I., the main period of gametogenesis occurs in late fall and early winter. In Dec. or Jan. the gonads of some clams already appear morphologically ripe. Gametogenesis in both sexes is slowed down during winter but is resumed at a rapid rate with the spring increase in temp. Spawning begins near the end of June or early in July when the water temp. is approx. 13.5[degree]C. The dates when 50% of the clam population should be expected to enter the stage of being ripe but not having begun to spawn, the stage of partial spawning, and the stage of complete spawning should fall within [plus or minus] 3 days of June 4, Aug. 13 and Oct. 6 respectively. In adult C. islandica the sexes are separate and well defined. Reversal of sex has not been recorded thus far. The eggs of these clams cannot be artificially fertilized. The appearance and behavior of cells of atypical spermatogenesis are discussed.