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Summary
Analysis of the gonadal index and seasonal cytological changes of the gonads of the Japanese limpet, Cellana nigrolineata (Reeves), covering two breeding seasons (July 1989 to November 1990) showed a marked reproductive cycle. A new method, equivalent circular diameter (d-circle), was employed in measuring the polygonal-shaped oocytes. Measurements were made of oocyte size and their frequency distribution, as well as the percent area occupied by the various stages of gametogenesis per gonadal acinus. The time of gonadal growth, maturation, spawning, post-spawning and resting was related to the annual sea temperature cycle. The gonads contained immature gametes in winter which later increased in size and occupied a greater area of the gonad. During the warm season (from July to September) gonads were full of mature oocytes and sperm, indicating that the breeding season occurs during this period.
