Immunochemical sexing of living yellowfin tuna, <i>Thunnus albacares</i> (Bonnaterre), using a vitellogeninlike protein

Abstract

Sexing of living yellowfin tuna, Thunnus albacares (Bonnaterre), was carried out based on immunochemical detection of vitellogenin (VTG), a female-specific protein. Tissue samples were taken from swimming fish in a sea pen by a hand-made apparatus. Recently fertilized eggs were also collected before tissue sample trials. A double immunodiffusion pattern showed that the egg homogenate of T. albacares reacted with rabbit antibody against the purified VTG of greater amberjack, Seriola dumerili (Risso). This suggests that the VTG of T albacares has an antigenicity similar to that of S, dumerili and that this antibody can be used to detect T albacares VTG. Immunodot-blotting analysis revealed that, out of the two fish tested, the tissue sample from one, but not the other, reacted with this antibody, suggesting that the former was a mature female, and the latter a male or immature female. Examination of the fish gonads revealed an ovary and a testis, respectively. Immunological and morphological results corresponded completely. Therefore, the method used in the present study is available for discriminating the sexes of T albacares.