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Continuous light administration during the photolabile period alters the natural endocrine profiles both at early and late gametogenesisi of sea bass

AutorRodríguez, Rafael ; Felip, Alicia ; Hala, Edmond; Zanuy, Silvia ; Carrillo, Manuel
Fecha de publicaciónsep-2011
EditorAsociación Ibérica de Endocrinología Comparada
Citación8º Congreso de la Asociación Ibérica de Endocrinología Comparada (2011)
ResumenThe objective of this study is to report the effect of the continuous light (LL) on endocrine profiles of male juvenile sea bass both at early and late gametogenesis during their first year of age. According to the photo-sensible period (August-September) recently identified in this species, six different LL regimes were applied as follows: 1) LL from August 1 to September 30 (W1-AS); 2) LL from September 1 to September 30 (W2-SS); 3) LL from August 15 to September 15 (W3-15AS); 4) LL from August 1 to August 30 (W4-AA); 5) positive control group or constant simulated natural photoperiod, and 6) negative control group or constant LL all year round (W6-LL). Steroid plasma levels (17-ß estradiol, E2 and 11-ketotestosterone, 11-KT) and brain content of gonadotropin-releasing hormone type 2 (GnRH2) have been analyzed both at early and late gametogenesis. Gonadosomatic index (GSI), and the rates of spermiating males have been also assessed. Our results show that E2 plasma levels of fish exposed to LL decreased earlier than those of control group during early gametogenesis. Similarly, plasma levels of 11-KT and GnRH2 brain content of fish exposed to LL, peaked 15 days before than those of control group, both at early gametogenesis and at late gametogenesis. Finally, the amplitude of the hormonal rhythms of fish exposed to LL was lower than those of control group, being more noticeable in those groups with lower GSI and rates of spermiation (i.e. W2-SS and W6-LL). These results suggest that the exposure to LL within the photo-sensible period is able to modify the hormonal profiles of juvenile males, thus reducing the number of early pubertal fish and their gonadal development. Likely, the alteration in the production of E2, 11-KT and GnRH2 caused by the photoperiod might be a limiting factor of the spermatogonial proliferation towards meiosis as well as of the onset of meiosis in the male sea bass. At late gametogenesis the dramatic decrease of 11-KT is highly correlated with the strong reduction of the gonadal development and the absence of spermiating fish. Presently, mRNA expression profiles of some target genes such as the anti-Müllerian hormone (amh) and the estrogen receptors (erß1 and erß2) are evaluated at the gonadal level to elucidate the molecular mechanisms involved in the reduction of sexual maturation.
DescripciónPonencia presentada en el 8º Congreso de la Asociación Ibérica de Endocrinología Comparada celebrado en Madrid del 5 al 7 septiembre 2011
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