Biopsy studies on the natural sex reversal in Monopterus albus (Pisces: Teleostei)



A technique for the study of the ontogenetic development and the sequential changes in structure of the gonad of Monopterus albus during natural sex reversal was established by making successive biopsy examinations on gonadal tissue of individual animals at regular time intervals. Results obtained from the present investigation provided some direct and conclusive evidence that anatomical transformation from an ovary, through a transitory intersexual phase, to a testis occurred as a natural process in the life cycle of individuals in this species, and confirmed most of the previous observations derived from studies based upon body-size and sexuality correlation. This biopsy approach will form a basis for further investigations on the effects of various experimentations, such as hormone administration, hypophysectomy, photo-stimulation and thermo-stimulation, on sex differentiation and sex changes in this protogynous hermaphroditic fish.