IBBEA   24401
INSTITUTO DE BIODIVERSIDAD Y BIOLOGIA EXPERIMENTAL Y APLICADA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
FOOD RESTRICTION STIMULATES FINAL MATURATION OF SPERMATOGENESIS AND INDUCES VARIATION IN LEPTIN-A EXPRESSION IN THE CICHLID FISH CICHLASOMA DIMERUS
Autor/es:
DANIELA I. PÉREZ SIRKIN; MARÍA P. DI YORIO; TOMAS H. DELGADIN; PAOLA J. KARP; GUSTAVO M. SOMOZA; PAULA G. VISSIO
Lugar:
Olhão
Reunión:
Congreso; 10 th International Symposium on Reproductive Physiology of Fish; 2014
Resumen:
Introduction In vertebrates, reproduction is affected by different factors including food availability. Leptin has been proposed in mammals as the link between nutritional status and reproduction, however in teleosts more studies are necessary to elucidate leptin function. There are many reports studying the effects of feeding on the reproductive axis of female fish, but fewer studies have been undertaken in males. In this context, the aim of the present study was to examine the effects of fasting on leptin-a expression and spermatogenesis in the South American cichlid fish Cichlasoma dimerus. Methods Cichlasoma dimerus pairs at the same reproductive stage (two days after spawning) were separately maintained for three weeks in small aquaria. Body weight and total length were recorded at the beginning of this experimental period. The fish were then daily fed with commercial pellets at 1.5% of their body weight or completely starved. At the end of the three weeks period, morphological parameters were recorded and the gonadosomatic and hepatosomatic index (GSI and HSI, respectively) were calculated. Testicular histology was performed and the proportion of the different spermatic cells was calculated along the testis. Gonadotropin releasing hormone I (GnRH I, the hypophysiotropic GnRH variant in this species), luteinizing hormone (LH) and follicle-stimulating hormone (FSH) mRNA levels were evaluated by real time PCR in the brain and pituitary gland respectively. In addition, leptin-a mRNA levels were studied in brain, liver and gonads. A Randomized Blocking Design ANOVA was used to evaluate differences between treatments. Results and Discussion The three weeks fasting resulted in a reduction of 6.5 % of the body weight. Fasted fish presented lower HSI with respect to fed ones, but no differences in GSI were observed between both groups. Nevertheless a great variation in the percentage of the different cell types in the testis was obtained. Starved males presented a statically greater proportion of spermatozoa (54.1% vs. 23.8%) but a lower proportion of primary spermatocytes (27.2% vs. 57%) comparing with fed males. However, no differences were obtained in the other testis cells proportions. Additionally, an increment in LH and FSH mRNA levels was observed in starved males, with no differences in GnRH I expression levels. With respect to leptin-a expression, starvation induced an up regulation in the liver, but a down regulation in the gonads and the brain. Conclusion Three weeks of starvation highly stimulates final maturation in C. dimerus and probably decreases the possibility of a new spermatogenetic cycle. Interestingly, in organs related with feeding and reproduction, leptin-a expression responses differentially to fasting protocol.