Gonadal sex differetiation through histological analysis and social structure were
investigated in anemone fish Amphiprion percula occuring in Andaman and
Nicobar islands. Field observation in different locations of Bay island showed
that this species is always seen in association with their host sea anemones
Heteractis magnifica H. crispa and Stichodactyla gigantea as small social groups
that include an adult pair and one to three juveniles (sub adults) and the largest
fish is usually the female and the next largest one is the functional male.
Considerable size difference consistently appeared between the sexually active
female and male, and noticed that a hierarchy exists in which the female is the
dominant individual in a social group. Histological examination of gonads
indicated that all juveniles start their life as male and subsequently changes
into females as they reach larger sizes and mature. Based on the histological
observation, the gonad was categorized into seven phases: immature phase, preripe
male phase, ripe male phase, transitional phase, pre-ripe female phase,
ripe female phase-I and ripe female phase-II. All the juveniles had ambosexual
gonads with testicular and ovarian tissues. Fishes in ripe female phase-II had
ovaries with many fully grown yolky oocytes and vitellogenic oocytes, which
were absent in ripe female phase-I, and characterized by the presence of many
perivitellogenic oocytes and an ovarian cavity but have no testicular tissue. The
study confirmed the sex reversal in A. percula from male to female (protandrous
hermaphroditism). The field study supported that social structure plays an
important role in its sex change
