海洋無脊椎動物の生殖腺の成熟に関する研究-V. : ミズクラゲの生殖腺にみられる季節的変化

概要

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In order to clarify the spawning season of the moon jelly, Aurelia aurita, one of the commonest medusa in the world, specimens were collected once a month during the period from April, 1969 to March, 1970, from Urazoko Inlet, one of the small inlets in Wakasa Bay on the west coast of the Japanese mainland. The gonads were removed from the collected specimens and examined histologically. The ripe sperm in the seminiferous tubules and ripe ova in the genital epithelium are released directly into the genital sinus, and from there move on to the gastro-circular groove. Next, passing through the gastro-oral arm groove, these gametes reach the basal groove of the oral arm, and finally are expelled from the body to the sea water. The spawning season may extend from December to June of the following year. Due to asynchronous developments of the gametes, release of these substances last for a fairly long time. Neither specimen with gonads of degenerative figure nor recovery phase was detected in the present examination.