Abstract:The annual maturation cycle of testis and variation of sex steroids level in male barfin flounder were investigated by histological and radioimmunoassay methods. The results showed that gametes exhibited five different phases during the annual development cycle, accordingly the testis maturation cycle can be divided into five stages. The biological parameters including gonadosomatic index (GSI), hepatosomatic index (HSI),and condition factor (CF) were also recorded and they exhibited reasonable variation during the testis maturation. The GSI began to increase in October and peaked in December, and then dropped dramatically and maintained until the next maturation cycle. The HSI value was relatively low during the annual cycle except in November and December. The CF value stayed at a high level from May to August and maintained a relative low level at other months. The serum testosterone level increased from September and peaked in December, then dropped to a relatively lower level until the next maturation cycle. Meanwhile, the serum estradiol level peaked in February and maintained at a relatively low level during the annual maturation cycle. These results highlight the reproductive biology of male barfin flounder, and can serve as useful reference for maturation regulation of male broodstocks.
