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Steelhead trout (Oncorhynchus mykiss) reared under two different regimes: high food ration for 1 year ([S.sub.1]; typical strategy) or low ration for 2 years ([S.sub.2]) were subjected to a seawater challenge during the corresponding spring outmigration period. The [S.sub.1] smolts were smaller and suffered greater seawater challenge mortality (23.9% compared with 0.7% for the [S.sub.2] smolts) that was significantly and negatively related to body size. Heritability of body size was similar for the two treatments during the parr stage (fork length: [S.sub.1] = 0.181, [S.sub.2] = 0.245; mass: [S.sub.1] = 0.372; [S.sub.2] = 0.447), but higher for the [S.sub.1] treatment during the smolt stage for length ([S.sub.1] = 0.212, [S.sub.2] = 0.002) and body mass ([S.sub.1] = 0.145, [S.sub.2] = 0.015). Strong family effects for both traits and significant family by environment interactions for parr mass and smolt length indicated significant phenotypic plasticity. A genetic response to size-selective mortality caused by insufficient growth opportunity in the [S.sub.1] treatment is plausible and may affect fitness in the natural environment through effects on correlated traits. Des truites arc-en-ciel anadromes (Oncorhynchus mykiss) elevees selon deux regimes distincts, soit de fortes rations alimentaires pendant 1 an ([S.sub.1], strategie typique) d'une part et de faibles rations alimentaires pendant 2 ans ([S.sub.2]) d'autre part, ont ete assujetties a une epreuve en eau de mer durant la periode de devalaison printaniere correspondante. Les saumoneaux [S.sub.1] etaient plus petits et presentaient une plus grande mortalite durant l'epreuve en eau de mer (23,9 % contre 0,7 % pour les saumoneaux [S.sub.2]) reliee significativement de maniere negative a la taille du corps. L'heritabilite de la taille du corps etait semblable pour les deux traitements au stade de tacon (longueur a la fourche : [S.sub.1] = 0,181, [S.sub.2] = 0,245; masse : [S.sub.1] = 0,372, [S.sub.2] = 0,447), mais plus grande pour le traitement [S.sub.1] au stade de saumoneau en ce qui concerne la longueur ([S.sub.1] = 0,212, [S.sub.2] = 0,002) et la masse corporelle ([S.sub.1] = 0,145, [S.sub.2] = 0,015). De forts effets familiaux pour les deux caracteres et des interactions famille-milieu significatives pour la masse des tacons et la longueur des saumoneaux indiquent une plasticite phenotypique significative. Une reaction genetique a une mortalite selective selon la taille causee par une possibilite de croissance insuffisante dans le traitement [S.sub.1] est plausible et pourrait avoir une incidence sur l'aptitude dans le milieu naturel par l'entremise d'effets sur des caracteres correles. [Traduit par la Redaction], Introduction Captive breeding programs can cause changes in phenotypic traits related to fitness in just a few generations (Frankham 2008; Fraser 2008). Genetic divergence in important life history traits can [...]

BACKGROUND: Polybrominated diphenyl ether (PBDE) flame retardants have been implicated as disruptors of the hypothalamic-pituitary-thyroid axis. Animals exposed to PBDEs impact TH-regulated pathways in target tissues. OBJECTIVE: We examined the [...]

The influence of salmon somatolactin (sSL) on transepithelial Pi and Ca2+ monoment is investigated using winter flounder renal proximal tubule primary monolayer cultures in Using chambers. Pi abstorption is stimulated by the (sSL) in a does dependent manner. The overall Pi reabsorptive flux is also significantly increased by the salmon growth hormones rat prolactin and sSL.

Abstract Background Throughout oogenesis, cell-cell communication via gap junctions (GJs) between oocytes and surrounding follicle cells (theca and granulosa cells), and/or amongst follicle cells is required for successful follicular development. To gain a fundamental understanding of ovarian GJs in teleosts, gene transcripts encoding GJ proteins, connexins (cx), were identified in the coho salmon, Oncorhynchus kisutch, ovary. The spatiotemporal expression of four ovarian cx transcripts was assessed, as well as their potential regulation by follicle-stimulating hormone (FSH), luteinizing hormone (LH) and insulin-like growth factor 1 (IGF1). Methods Salmonid ovarian transcriptomes were mined for cx genes. Four gene transcripts designated cx30.9, cx34.3, cx43.2, and cx44.9 were identified. Changes in gene expression across major stages of oogenesis were determined with real-time, quantitative RT-PCR (qPCR) and cx transcripts were localized to specific ovary cell-types by in situ hybridization. Further, salmon ovarian follicles were cultured with various concentrations of FSH, LH and IGF1 and effects of each hormone on cx gene expression were determined by qPCR. Results Transcripts for cx30.9 and cx44.9 were highly expressed at the perinucleolus (PN)-stage and decreased thereafter. In contrast, transcripts for cx34.3 and cx43.2 were low at the PN-stage and increased during later stages of oogenesis, peaking at the mid vitellogenic (VIT)-stage and maturing (MAT)-stage, respectively. In situ hybridization revealed that transcripts for cx34.3 were only detected in granulosa cells, but other cx transcripts were detected in both oocytes and follicle cells. Transcripts for cx30.9 and cx44.9 were down-regulated by FSH and IGF1 at the lipid droplet (LD)-stage, whereas transcripts for cx34.3 were up-regulated by FSH and IGF1 at the LD-stage, and LH and IGF1 at the late VIT-stage. Transcripts for cx43.2 were down-regulated by IGF1 at the late VIT-stage and showed no response to gonadotropins. Conclusion Our findings demonstrate the presence and hormonal regulation of four different cx transcripts in the salmon ovary. Differences in the spatiotemporal expression profile and hormonal regulation of these cx transcripts likely relate to their different roles during ovarian follicle differentiation and development.

Abstract Background The aim of this study was to identify differentially expressed ovarian genes during primary and early secondary oocyte growth in coho salmon, a semelparous teleost that exhibits synchronous follicle development. Methods Reciprocal suppression subtractive hybridization (SSH) libraries were generated from ovaries with perinucleolus (P) or cortical alveolus (CA) stage follicles and selected genes were assessed with quantitative PCR (qPCR). An assessment of changes in RNA composition during oocyte growth and its relationship to transcript levels was also conducted. Results SSH revealed several differentially expressed genes during early oogenesis, some which will not likely be utilized until 1–3 years later in salmon. Zona pellucida glycoprotein (zp) genes, vitellogenin receptor (vldlr) isoforms, cathepsin B (ctsba), cyclin E (ccne), a DnaJ transcript (dnaja2), and a ferritin subunit (fth3) were significantly elevated at the P stage, while a C-type lectin, retinol dehydrogenase (rdh1), and a coatomer protein subunit (cope) were upregulated at the CA stage. Putative follicle cell transcripts such as anti-Müllerian hormone (amh), lipoprotein lipase (lpl), apolipoprotein E (apoe), gonadal soma-derived growth factor (gsdf) and follicle-stimulating hormone receptor (fshr) also increased significantly at the CA stage. The analysis of RNA composition during oocyte growth showed that the total RNA yield and proportion of messenger RNA relative to non-polyadenylated RNAs declined as oogenesis progressed. This influenced apparent transcript levels depending on the type of RNA template used and normalization method. Conclusion In coho salmon, which exhibit a dramatic change in oocyte size and RNA composition during oogenesis, use of messenger RNA as template and normalization of qPCR data to a housekeeping gene, ef1a, yielded results that best reflected transcript abundance within the ovarian follicle. Synthesis of zp transcripts and proteins involved in yolk incorporation and processing occurred during primary growth, while increased expression of a CA component and genes related to lipid incorporation occurred concomitant with the appearance of CA, but prior to lipid accumulation. Significant increases in transcripts for fshr, gsdf, and amh at the CA stage suggest a role of FSH and TGFβ peptides in previtellogenic oocyte growth and puberty onset in female salmon.

Studies of microinjection of linear pOnMTGH1 DNA, a genetic construct consisting of the metallothionein-B promoter coupled to the type-1 growth hormone gene, into the blastodisc area of coho salmon eggs whose growth is arrested following fertilization reveal that pOnMTGH1 construct is vital for growth acceleration. The transgenic fishes containing pOnMTGH1 formed a silver body coloration and were markedly larger than non-transgenic fishes. Transgenic fishes also exhibited high winter levels of growth hormone.