Suchergebnisse

34 p., 5 figures and references ; The aquaculture of Senegalese sole (Solea senegalensis) is limited by the failure of cultured breeders (F1 generation) to produce fertilized spawning. Critical reproductive dysfunctions have been observed in both female and male Senegalese sole cultured breeders, including reduced fecundity and diminished sperm production. The present work aimed to study the effectiveness of different hormonal treatments on the stimulation of male reproduction. Male Senegalese sole cultured breeders were treated with 1) saline injections (controls), 2) gonadotropin-releasing hormone agonist (GnRHa) injections (25μgkg-1), 3) GnRHa slow release implants (40μgkg-1) or 4) human chorionic gonadotropin (hCG) injections (1000IUkg-1). Each group of males was placed in separated spawning tanks together with females treated with GnRHa implants.All three hormonal treatments increased plasma testosterone (T) and 11-ketotestosterone (11-KT) levels and the gonadosomatic index (GSI), with highest effects exerted by the hCG treatment. Histological examination of the testes showed no effect of the GnRHa injection, but a clear stimulation of germ cell proliferation and testicular maturation by GnRHa implants and hCG injections. As expected, GnRHa implantation of females induced egg release in all experimental tanks and interestingly, female fecundity increased in tanks containing GnRHa- or hCG-treated males. A fertilized spawning was obtained only from the group containing hCG-treated males. In conclusion, hormonal treatments stimulated steroidogenesis and spermatogenesis in male Senegalese sole, with highest efficiency of the hCG multiple injection treatment. Female fecundity was affected by the hormonal treatment applied over the accompanying males, suggesting a pheromone communication between fish. However, none of the treatments seemed to be adequate in solving the problem of lack of fertilized spawning in cultured Senegalese sole broodstocks. ; This research was funded by the Spanish Ministry of Education and Science (MEC) (Project AGL2003-07670), the Ministry of Agriculture, Fisheries and Food (Project JACUMAR 2006, II National Plan for the Cultivation of Sole) and the Regional Government of Valencia (ACOMP06/211) to E.M.; and by a Spanish-Greece Collaborative Action funded by the MEC (HG2004-028) and the General Secretariat for Research and Technology, Greece, to E.M. and C.C.M. J.M. Guzmán received a FPI fellowship from the MEC.

43 p., 2 tablas, 7 figuras y bibliografía ; The aquaculture of Senegalese sole (Solea senegalensis) is limited by the poor spawning performance of the F1 generation cultured broodstock. The present study compared the efficiency of two sustained-release delivery systems loaded with gonadotropin-releasing hormone agonist (GnRHa) and a single GnRHa injection on the stimulation of oocyte maturation (OM), sex steroid hormone secretion and spawning. Analysis with an ELISA showed that the administered GnRHa was no longer detectable in the plasma 3, 7 and 14 d after administration via a single injection, microspheres and an implant, respectively. All GnRHa treatments induced a transient elevation of testosterone (T) and 17beta; estradiol (E2) plasma levels after 1-3 d. Only three spawns were obtained from controls on days 35, 41 and 42 of the study and ovarian biopsies showed abundant fully vitellogenic oocytes, but little OM. Fish given a GnRHa injection spawned sporadically with the first spawn at 20 days post-treatment (dpt). In contrast, GnRHa implants and microspheres stimulated OM and daily spawning starting at 4 and 5 dpt, respectively, and lasting for a period of 28 d. Total fecundity in the broodstock treated with GnRHa-delivery systems was 15-22 times greater than controls and 3-5 times greater than GnRHa-injected fish. Although egg quality appeared to be high, no fertilization was obtained. The results suggest that GnRHa-delivery systems are highly efficient on stimulating OM and spawning in Senegalese sole, presumably through the long-term elevation of pituitary luteinizing hormone release, which in turn stimulated the appropriate changes in ovarian steroidogenesis. However, the effectiveness of the treatment was negated by possible dysfunctions of the male breeders or of the reproductive behavior of the broodstock. ; This research was funded by the Spanish Ministry of Education and Science (MEC) (Project AGL2003-07670), the Ministry of Agriculture, Fisheries and Food (Project JACUMAR 2006, II National Plan for the Cultivation of Sole) and the Regional Government of Valencia (ACOMP06/211) to E.M.; and by a Spanish-Greece Collaborative Action funded by the MEC (HG2004-028) and the General Secretariat for Research and Technology, Greece, to E.M. and C.C.M. ; Peer reviewed

12 páginas, 8 figuras, 2 tablas. ; The Senegalese sole (Solea senegalensis) is a valuable flatfish for aquaculture, but it presents important reproductive problems in captivity. Spawning is achieved by wild-caught breeders but cultured broodstocks fail to spawn spontaneously and, when they do, eggs are unfertilized. To gain knowledge on the physiological basis underlying this reproductive dysfunction, this study aimed at analyzing comparative hormone levels between wild and cultured broodstocks at the spawning season. The Senegalese sole gonadotropin (GTH) subunits, FSHβ, LHβ and GPα, were cloned and qualitative (in situ hybridization) and quantitative (real-time PCR) assays developed to analyze pituitary GTH gene expression. In females, FSHβ and GPα mRNA levels were higher in wild than in cultured broodstocks, whereas in males all three subunits were highest in cultured. By ELISA, three GnRH forms were detected in the pituitary, displaying a relative abundance of GnRH2 > GnRH1 > GnRH3. All GnRHs were slightly more abundant in wild than cultured females, whereas no differences were observed in males. Plasma levels of vitellogenin and sex steroids were also analyzed. Results showed endocrine differences between wild and cultured broodstocks at the spawning period, which could be related to the endocrine failure of the reproductive axis in cultured breeders. ; This research was funded by the Spanish Ministry of Education and Science (MEC) (AGL2006-13777-C01), the Ministry of Agriculture, Fisheries and Food (MAPA) (JACUMAR, II National Plan for the Cultivation of Sole) and the Regional Government of Galicia (PGIDIT06RMA004E). J.M. Guzmán received a FPI fellowship from the MEC. J.B. Ortiz-Delgado was supported by the "Ramón y Cajal" program (MEC, Spain). ; Peer reviewed