MONITORING OF TESTOSTERONE AND OESTRADIOL LEVELS IN BLOOD PLASMA OF MUTTON SNAPPER LUTJANUS ANALIS FEMALES MAINTAINED UNDER TWO DIFFERENT THERMOPERIOD CONDITIONING CYCLES

Abstract

Two groups of adult Mutton snapper fish Lutjanus analis captured in the wild, each one of three females and four males, were kept during eight months under controlled temperature and photoperiod conditions in the lab in order to stimulate their sexual maturation which was in a state of latency because of the effects of confinement. The first group was maintained under an artificial cycle with temperature manipulation and the second under a control cycle, in which this parameter was left at natural conditions. Every two months blood samples from all females were taken for the analysis of plasma testosterone (T) and oestradiol (E2) levels, taking ovarian biopsies simultaneously to register the mean diameter of the oocytes. After six months, a significative increase in the mean diameter of the oocytes of the three females of the artificial cycle was observed, with coincidence and statistic relationship with the increase in the T and E2 (r = 0.62 y 0.82 respectively). No oocyte growth was observed in the females under the control cycle. In both, artificial and control cycles, T and E2 levels showed a close relationship with photoperiod (r = 0.84 y r = 0.61) while temperature showed a lower or non significant relationship (r = 0.40 y r = 0.20). Statistical differences (P<0.1) were found between the condition factors of the two groups, while the sexual steroids didn’t show any differences between them. The present work constitutes the first report on the analysis of sexual steroid levels during the gonadal maturation process in fish of the Family Lutjanidae kept under an artificial conditioning cycle.