Reproductive cycle of the helmet crab (Telmessus cheiragonus)

Reproductive cycle of the helmet crab (Telmessus cheiragonus)

J. Nagao and H. Munehara

Reproductive cycle of the helmet crab (Telmessus cheiragonus)This is part of Crabs in Cold Water Regions: Biology, Management, and Economics
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To clarify the annual reproductive cycle of the helmet crab, Telmessus cheiragonus, in the coastal regions of Usujiri, southern Hokkaido, Japan, the gonads of a total of 266 adult crabs (148 males and 118 females) were examined histologically. Ovarian maturity was divided into five stages (stages 1-5). The ovaries were immature (stage 1 or stage 2) during October-March and maturing during April-September. The females became ovigerous during October-January. In males, the developmental stage of thet esticular lobules was divided into six stages (stages I-VI). All stages were observed throughout the year but immature lobules (stages I-IV) occurred most frequently in May-June. The mating season was estimated to between March and July with a peak of mating activity in May. This information was based on the occurrence of soft-shell females. From a result of these observations, the annual reproductive cycle of this species is estimated to require a year and was divided into the ovarian maturation phase (April-September) and the incubation phase (October-March). During the ovarian maturation phase, the molting of the females and subsequent mating seemed to occur frequently. During the incubation phase, most females maintained immature ovaries. Inhibition of ovarian maturing during the incubation phase may be a characteristic of the reproductive cycle of this species.

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