Analysis of the relationship between gonads and hepatopancreas in males and females of the crab Sesarma intermedia, with reference to resource use and reproduction

Abstract

At the beginning of the reproductive period in May, there was an increment in both the gonad and heaptopancreas. During the peak phase in June, with high ovary production, there was a decrease in the hepatosomatic index (HSI), particularly for the Ariake females. The minimum gonadosomatic index (GSI) of 2% in August and September for the Ariake and in September and October for the Hakata populations was inversely related to the increase of HSI. A second rise in GSI was observed in November at the 1% level as against the June peak of 5% for the Ariake and 3.5% for the Hakata females, and it remained at this level until December, while the HSI decreased to the minimum. The December minima for both GSI and HSI were about the same as the initial February values. The spermathesomatic index (SSI) had a slight increase to 0.8% in August, but remained constant at 0.5% throughout the year. Likewise, GSI for males was constant at the 0.5% level, with minor fluctuations, and did not show any clear relationship with the HSI as for female GSI. Females had higher hepatosomatic indices but the soma weighed less than males throughout the year. Again in May, medium-sized females had the highest GSI followed by large and then small-sized individuals. As the HSI steadily decreased, GSI increased with advancing egg development stages for ovigerous females. The quantitative stomach analyses showed that females had higher stomach quantity indices (SQI) in May than in September, when the breeding period had ended. Contrary results were observed for males. Also, female SQI in May was higher than that for males.