Effects of light and temperature conditions on the expression of GnRH and GtH genes and plasma steroids levels in Odontesthes bonariensis females

LEANDRO ANDRÉS MIRANDA; CARLOS AUGUSTO STRÜSSMANN; GUSTAVO MANUEL SOMOZA

FISH PHYSIOLOGY AND BIOCHEMISTRY

Kluwer

Año: 2009 vol. 35 p. 101 - 108

0920-1742

The present study examined the endocrine mediation between environmental factors (temperature and photoperiod) and the brain-pituitary-gonadal axis in females of pejerrey Odontesthes bonariensis. For this purpose, we analyzed the changes in the expression of brain gonadotroping releasing hormones (GnRHs) and gonadotropin (GtH) subunits (FSH-¥â, LH-¥â, GPH-¥á) genes, plasma gonadal steroids [estradiol (E2) and testosterone (T)], gonadal histology, and gonadosomatic index (GSI) in adult females that were exposed to combinations of short (8 hr) or long (16 hr) photoperiods and low (12¢ªC) or high (20¢ªC) temperatures after winter conditions (8 hr light, 12¢ªC). Pejerrey females kept under the short photoperiod had low GSIs and ovaries containing only previtellogenic oocytes regardless of the experimental temperature. In contrast, females exposed to the long photoperiod presented high GSIs and ovaries with vitellogenic oocytes at both temperatures. These fish also had significantly higher expression of sGnRH, pjGnRH, cGnRH-II, FSH-¥â, LH-¥â and GPH-¥á genes and plasma E2 levels than those at the shorter photoperiod. No significant changes were observed in plasma T levels. In conclusion, it was demonstrated that the increase of the day length but not that of temperature triggers the maturation of pejerrey females after the winter period of gonadal rest, and that this occurs by an integrated stimulation of the various components of the brain-pituitary-gonad axis.