Expression of three GnRH forms, FSH-â and LH-â subunits during sex differentiation and at different gonadal stages in the pejerrey fish, Odontesthes bonariensis.

GASTON GUILGUR, LEONARDO; STROBL MAZZULLA, PABLO HERNAN; JUAN IGNACIO FERNANDINO; ANDRES MIRANDA, LEANDRO; GUSTAVO MANUEL SOMOZA

Buenos Aires

Jornada; VII Jornadas Multidisciplinarias de la Sociedad Argentina de Biología.; 2005

IBYME

GnRH plays a pivotal role in the reproduction of all vertebrates. The primary function is to stimulate the synthesis and release of LH and FSH. The presence of three GnRH variants is a common pattern in teleosts; however, the role of each form is not known. In this context, the objective of this work was to follow GnRHs and GtHs expression at different gonadal stages in pejerrey by semiquantitative-PCR. Also, GnRH gonadal expression was determined. The pejerrey possesses marked thermolabile sex determination and it was showed that the number of GnRH neurons in the preoptic area peaked during the temperature sensitive window. GnRH expression was also measured during the sex differentiation period. In adult fish, at the brain-pitutary level, pejerrey females showed a tendency to increase the mRNA levels of the three GnRH forms during mid vitellogenesis compared to previtelogenic and post-spawning stages. Males did not show a clear pattern maybe due to the fact that they showed an expanded spermiating period. At the pituitary level only the hypothalamic GnRH (pjGnRH) form was shown to be expressed at all stages. With respect to both gonadotropins a tendency to show a greater expression during early stages of gonadogenesis was observed in both sexes as already demonstrated in other multiple spawner teleost species. GnRH variants were also demonstrated to be expressed either at the ovaries and testis. The expression pattern of GnRHs in the gonads also showed seasonal and stage-dependent variations. These results represent the first step to understand the function of different GnRH forms in the teleost brain and gonads.