Glucocorticoid receptor (DlGR1) is expressed in pre-larval and larval stages of the teleost fish Dicentrarchus labrax

Glucocorticoid hormone receptors (GR), members of the nuclear hormone receptor superfamily, are ligand-dependent transcription factors expressed in various tissues by binding to specific DNA sequences. Since glucocorticoids have a role in maintaining the homeostatic status in fish, we previously cloned and sequenced a GR (DlGR1) of adult Dicentrarchus labrax; we also showed mRNA expression (in situ hybridization) and tissue immunohistochemical localization of DlGR1 in several organs. This work has now been extended to the examination of the expression, tissue distribution, and cytolocalization of DlGR1 in larval developmental stages by similar methods to those used for the adult organs. The riboprobe included the DlGR1 cDNA transcriptional activation domain (1.0–1,300 nucleotide sequence) showing no significant similarity with a known second GR cDNA sequence of sea bass. The antibody was specific for an opportunely selected peptide sequence of the DlGR1 transcriptional domain. In histological sections of brain, head kidney, gills, liver, anterior intestine, and spleen cells, the riboprobe was mainly located in the cell nucleus. The antibody identified DlGR1 in the head kidney, gills, liver, and anterior intestine, mainly located in the cytosol. These results are in agreement with the receptor location in adult tissues. The greater presence of both the transcript and protein of DlGR1 in the late developmental stages suggests an increasing expression of this receptor. The cytolocalization (nuclear-cytosolic) and presumptive roles of DlGR1-containing tissues are discussed

Physiological colour changes in the red porgy, Pagrus pagrus, following adaptation to blue lighting spectrum

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How does fish metamorphosis affect aromatic amino acid metabolism?

Aromatic amino acids (AAs, phenylalanine and tyrosine) may be specifically required during fish metamorphosis, since they are the precursors of thyroid hormones which regulate this process. This project attempted to evaluate aromatic AA metabolism during the ontogenesis of fish species with a marked (Senegalese sole; Solea senegalensis) and a less accentuated metamorphosis (gilthead seabream; Sparus aurata). Fish were tube-fed with three l-[U-14C] AA solutions at pre-metamorphic, metamorphic and post-metamorphic stages of development: controlled AA mixture (Mix), phenylalanine (Phe) and tyrosine (Tyr). Results showed a preferential aromatic AA retention during the metamorphosis of Senegalese sole, rather than in gilthead seabream. Senegalese sole’s highly accentuated metamorphosis seems to increase aromatic AA physiological requirements, possibly for thyroid hormone production. Thus, Senegalese sole seems to be especially susceptible to dietary aromatic AA deficiencies during the metamorphosis period, and these findings may be important for physiologists, fish nutritionists and the flatfish aquaculture industry

Hormonally mediated maternal effects shape offspring survival potential in stressful environments

In most egg-laying vertebrates, maternal responses to stressful conditions are translated into the release of glucocorticoid hormones such as cortisol, which are then transmitted to their developing embryos. Although such maternally transmitted hormonal resources have been shown to influence or even interfere with the optimal developmental trajectories of offspring in many taxa, their influence on the dynamics of wild fish populations remains largely unexplored. Here, we examined the extent to which simulated hormonally mediated maternal effects influence the development and early survival of the coral reef damselfish, Pomacentrus amboinensis. Concentrations of cortisol in the eggs were manipulated within naturally occurring limits by immersion. We found that the proportion of embryos that delayed hatching when exposed to high levels of cortisol was considerably lower than in the other two treatments (low cortisol dose and control). High cortisol levels in P. amboinensis eggs resulted in increased egg mortality and greater asymmetry in hatchlings. For embryos that successfully hatched, individuals from the elevated cortisol treatments (especially low dose) survived longer after hatching. Although individuals that originated from eggs with elevated cortisol levels survived longer after hatching, they may not gain an overall survival advantage. Our results suggest that subtle increases in the allocation of maternally derived hormones, such as cortisol, to offspring are a direct way for stressed mothers to endow their young with an immediate survival advantage. We propose that this immediate benefit outweighs the developmental costs which may be expressed as reduced fitness at later life stages

Identification of a b1 integrin isoform with restricted tissue expression in a teleost fish.

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Dietary Lecithin Source Affects Growth Potential and Gene Expression in Sparus aurata Larvae

13 páginas, 5 figuras, 7 páginas.Soybean lecithin (SBL), used as a phospholipid source in larval fish diets, may compromise growth and survival in marine species, and affect gene expression, due to differences in fatty acid composition relative to marine lecithins (ML). The potential of SBL as a phospholipid source in gilthead seabream microdiets as compared to ML was evaluated. Two stocking densities were tested in order to exacerbate possible dietary effects: 5 and 20 larvae L−1. Larvae reflected dietary fatty acid profiles: linoleic acid was higher, whereas eicosapentaenoic and arachidonic acids were lower in SBL fed groups than in ML fed larvae. Highest stocking density decreased survival, and led to elevated saturates and lower docosahexaenoic acid levels in polar lipid. Muscle histology observations showed hindered growth potential in SBL fed larvae. Despite similar cortisol levels between treatments, higher glucocorticoid receptor (GR), as well as hormone-sensitive lipase (HSL) mRNA levels in SBL fed groups revealed a role for fatty acids in gene regulation. Further analysed genes suggested these effects were independent from the hypothalamus-pituitary-interrenal axis control and the endocannabinoid system. Cyclooxygenase-2 and gluconeogenesis seemed unaffected. For the first time in fish, a link between dietary lecithin nature and HSL gene transcription, perhaps regulated through GR fatty acid-induced activation, is suggested. Enhanced lipolytic activity could partly explain lower growth in marine fish larvae when dietary ML is not provided.This study was funded by Consejería Innovación, Ciencia y Empresa, Junta de Andalucía (Spain) which is co-financed by FEDER (project P06-AGR-01697 to M. Yúfera). Publication benefits from participation in LARVANET COST action FA0801.Peer reviewe