The 5¢ flanking region (1712 bp) of the growth hormone (GH) gene of the gilthead sea bream Sparus aurata was cloned, sequenced and characterized. It contains a consensus sequence for TATA box and several Pit-1 binding site motifs. Consensus sequences related to cyclic AMP response element, glucocortiocoid response element, and several other transcription factors were identified by comparison to consensus sequences in fish or mammalian GH genes. The promoter contains two microsatellites (di-and tri-nucleotides repeats) with additional upstream microsatellites (triand tetranucleotides), 10-mer tandem repeat, and two long inverted repeats. Analysis of the proximal dinucleotide microsatellite by polymerase chain reaction revealed polymorphism among individuals from a hatchery population and an association of alleles 250 and 254 with growth performance. Segregation analysis of this marker in one family showed Mendelian inheritance. These results suggest that the microsatellite in the promoter region (termed saGHpCA) might be considered as a candidate genetic marker for broodstock management and growth selection programs of Sparus aurata.
European sea bass Dicentrarchus labrax of the north-western (NW) and south-eastern (SE) Mediterranean Sea strains were exposed to different temperatures (13, 17 or 21 C) during the larval rearing (11-51 days post hatching, dph) or nursery periods (55-95 dph), in order to examine the effects of temperature on sex differentiation and subsequent growth during the first year of life. Higher growth was observed during exposure to higher temperatures, but fish of the NW strain exposed to 13 or 17 C during larval rearing exhibited compensatory growth once exposure to the lower temperatures finished, and as a result their final size at 300 dph was similar or greater to the group exposed to 21 C. Fish exposed to 17 C during the nursery period also had similar size to fish exposed to 21 C after 300 days of rearing, but the fish exposed to 13 C remained significantly smaller (ANOVA, n ¼ 55-100, P < 0Á05). There were significant differences in the sex ratio among the fish exposed to different temperatures during the two periods of rearing, with high temperature (21 C) resulting in a significantly higher percentage of males in the population, both in the NW (ANOVA, n ¼ 2, P < 0Á04) and SE populations (ANOVA, n ¼ 2, P < 0Á01). The masculinization effect of high temperature was significantly stronger during the larval rearing stage, both in the NW (ANOVA, n ¼ 2, P < 0Á005) and SE populations (ANOVA, n ¼ 2, P < 0Á01). None of the temperature manipulations could produce 100% females, suggesting that there is a part of the genetic component in sex differentiation which is not labile to environmental influence. # 2005 The Fisheries Society of the British Isles
The experiments were designed to evaluate the suitability for mariculture of the diploid and triploid hybrids of gilthead seabream Sparus aurata and red seabream Pagrus major, both of which are members of the Sparidae family. Performance testing of the hybrids was carried out in comparison with the parental species under the same controlled environment. The reciprocal diploid hybrids as well as the triploid hybrid did not exhibit any significant growth advantage over diploid parental species either before or after sexual maturity. The adults, both reciprocal diploid hybrids and triploid hybrid (female S. aurata× male P. major), were clearly immature and had only vestigial gonads; neither ovaries nor released milts were observed. Histological examination of the gonads, carried out during associated periods of the first and second maturation cycles of the parental species, showed that all the hybrids were completely sterile. Despite their sterility, the growth of the hybrids did not display any positive effect, and for this reason their commercial culture appears to be questionable. On the other hand, the use of sterilization through hybridization and chromosome set manipulation may be important when there is a need to restrict the ecological impact on a wild population.
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