The gonadal cycle of the captivity-reared hermaphroditic teleost Sparus aurata (L.) during the first two years of life

The gonadal cycle of the hermaphroditic teleost Sparus aurata reared in captivity was studied during the first two years of life.Until the age of 8 months, the dorsal ovarian part of the bisexual gonad was dominant.Towards the first breeding season at the end of the first year of life, the ventral testicular part of the gonad proliferated, forming a mature testis.At the end of the first breeding season, all the fish began to undergo sex reversal.From the age of 17 months, development proceeded in two directions : in about 80 p. 100 of the population the sex reversal process was completed and the individuals developed into females ; in the rest of the population the sex reversal process was not completed and the individuals developed into males.Introduction.Normal hermaphroditism and sex reversal are well-known phenomena in Teleostei (Atz, 1964 ; Reinboth, 1970).Pasquali (1941) and d'Ancona (1941,1949), studying the gonadal cycle of Sparus aurata caught in the Adriatic Sea, demonstrated protandrous hermaphroditism in this species.These authors found that the entire population functions as males at the end of the second year of life, then changes sex and performs as females from the end of the third year.The goal of the present research was to carry out an histological study of the gonadal cycle of S. aurata, based on captivity-reared fish of known age. Materials and methods.Fry of S. aurata about 20 mm long were collected in their natural habitat in the Mediterranean sea once a year at the end of March.They were stocked at densities up to 5 kglm 3 in outdoor experimental tanks according to 2 age classes, i. e. 4 months