Gametogenesis

A consequence of the initial differentiation of the gonads in teleosts with separate sexes (i.e. gonochoristic species) is the canalisation of the development of the gonads into either ovaries or testes. The development of the gonads during gametogenesis can be described at a macroscopic level using two basic indices, maturation staging and the gonadosomatic index (GSI). Oogenesis is the developmental process by which oogonia are transformed into mature oocytes ready to be ovulated. In group synchronous and asynchronous ovaries, the physiological control of oocyte development is more complicated than in synchronous ovaries. The dynamics of spawning have a major consequence for the fecundity of the female. As for oogenesis, the temporal sequence of spermatogenesis is regulated by the gonadotrophins secreted by the pituitary gland, follicle-stimulating hormone (FSH) and luteinising hormone (LH).