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The present studywas aimed to evaluate the capacity of common dentex (Dentex dentex) toefficiently use dietary carbohydrates. So, the effects of different type and levels of carbohydrates on growth performance, feed utilization, fish composition, plasmametabolites and keymetabolic pathways in liver andwhite muscle of common dentex are presented. Nine isonitrogenous (43%) and isoenergetic (22MJ kg−1) diets were formulated combining three types, pregelatinized starch (PS), dextrin (Dx) andmaltodextrin (Mx), and three levels (12, 18 and 24%) of carbohydrates. Growth performancewas not significantly influenced by treatments. The best feed utilizationwas observed in 18% Mx group. Higher hepatic lipid content was found in fish fed lower dietary carbohydrate levels. PS induced higher liver and white muscle hexokinase and pyruvate kinase activities compared to the lower values observed for Mx. Malic enzyme and glucose 6-phosphate dehydrogenase in liver and white muscle were lower in Mx group. The influence of dietary carbohydrates source was more noticeable than those induced by the carbohydrate level, when glycolysis and lipogenesis pathways were considered. Common dentex is able to use properly dietary carbohydrates, although optimal dietary inclusion levels are below 24%. The greater protein-sparing effect was promoted by the less complex carbohydrate (maltodextrin) and the best feed utilization indices were obtained at intermediate levels of inclusion (18%). SI

the intestine of marine fishes contributes to the ocean carbon cycle producing carbonate aggregates as part of the osmoregulatory process. Therefore, this study aimed to evaluate physiological adjustments of European sea bass (Dicentrarchus labrax) intestine to a higher pCO(2) environment likely in the near future (similar to 1700 mu atm). At the whole-body level, hypercapnia for 5 weeks resulted in fish having a significantly diminished specific growth rate, condition factor and hepatosomatic index. An increase in plasma osmolality and HCO3- concentration was detected, paralleled by decreased metabolites concentrations. In the intestine, high seawater pCO(2) was without effect on ouabain-sensitive ATPase activities, while Bafilomycin A1-sensitive ATPase activity significantly decreased in the anterior intestine. Anterior and mid intestine were mounted in Ussing chambers in order to measure bioelectrical parameters and bicarbonate secretion by pH-Stat ex-vivo. Hypercapnia induced a 2.3 and 2.8-fold increase in bicarbonate secretion rates in the anterior and mid intestine, respectively. In the intestinal fluid, HCO3- concentration increased 2.2-fold, and carbonate precipitates showed a 4.4-fold increase in response to hypercapnia, paralleled by a > 3-fold increase of drinking and a > 2-fold increase of intestinal volume at any given time. At the molecular level, hypercapnia elicited higher intestinal mRNA expression levels for atp6v1b (V-ATPase B subunit), slc4a4, slc26a3, and slc26a6, both in the anterior and mid intestine. As a whole, our results show that the intestine of sea bass responds to high seawater pCO(2), a response that comes at a cost at the whole-body level with an impact in the fish specific growth rate, condition factor, and hepatosomatic index. European Social Funds through the Portuguese National Science Foundation (FCT)[PTDC/MAR-BIO/3034/2014] Portuguese Foundation for Science and Technology (FCT) [UID/Multi/04326/2019] Ministry of Science and Higher Education, Portugal info:eu-repo/semantics/publishedVersion

In 2019, Europe will adopt a no-discards policy in fisheries. This entails the landing of captured species unless strong evidence is provided supporting their survival and recovery after fishing. Thus, research on this topic is gaining momentum. Bottom-trawling, as a non-selective fishing method, is characterized by a high proportion of discards including vulnerable key species, such as demersal sharks. Their survival may also depend on capture depth. By paralleling onboard and laboratory experiments with the small-spotted catshark, Scyliorhinus canicula, we offer a robust experimental design to assess the survival of discarded sharks. Catsharks were captured by bottom-trawling at two depths (shallow similar to 89 m and deep similar to 479 m). Blood samples were collected following trawl capture and analyzed for stress biomarkers (lactate, osmolality, phosphate, urea). During recovery in onboard tanks, behavior was video-recorded and fish were re-sampled after 24 h. A second experiment was conducted in laboratory facilities to simulate air-exposure after trawling and to analyze the physiological recovery. Our results showed that 95.7% of the animals survived 24 h after trawling. We confirmed that trawling elicited acute stress responses in catshark but that they managed to recover. This was demonstrated by lactate concentrations that were 2.6 mM upon capture, but recovered to assumed baselines after 24 h (0.2 mM). Non-invasive video monitoring revealed behavioral differences with depth, whereby those captured at 89 m depth required longer to recover than those captured at 479 m depth. Implementation of standardized survival studies by fishery managers can benefit from holistic physiological approaches, such as the one proposed here. European Social Funds through the Portuguese National Science Foundation (FCT)Portuguese Foundation for Science and Technology [PTDC/MAR-BIO/3034/2014] Project SUREDEPAR (Programa Pleamar, Ministerio de Agricultura y Pesca, Alimentacion y Medio Ambiente) Ministerio de Economia y CompetitividadSpanish Government [AGL2013-48835-C2-R, AGL2016-76069-C2-1-R] Ministry of Science and Higher EducationMinistry of Science and Higher Education, Poland FCTPortuguese Foundation for Science and Technology [UID/Multi/04326/2013] European UnionEuropean Union (EU) PADI Foundation [28467]

Halobatrachus didactylus, a marine teleost found in coastal lagoons and river estuaries is often exposed to important salinity changes. Despite its aglomerular kidney, it is able to survive in hypo-osmotic environments, likely via compensatory actions from gills and intestine. We aimed at evaluating the response of the branchial tissue of H. didactylus to salinity changes. Fish allocated into 15 groups were exposed to different salinities (0, 5, 12, 36 and 55 ppt) for 4, 24 and 96 h. At each time point, blood samples were taken and osmolality, glucose and ion concentration determined. Fish were sacrificed and gill samples collected for measurement of Na+/K+-ATPase activity and fixed for histology and immunohistochemistry. Mortality occurred only in the 0 ppt group, in which all fish died within 48 to 96 h. Blood osmolality was significantly conditioned by environmental salinity, increasing at 55 ppt and dropping at 5 and 0 ppt. At 4 h, glucose levels were higher in fish in altered salinity than in those in the 100% seawater group, possibly an indication of the adaptive effort required. Adjustments in Na+/K+-ATPase activity were seen at 24 and 96 h after transfer, in a characteristic u-shape, peaking at extreme low and high salinities. Contrary to most teleosts, the chloride cells in H. didactylus are located in the secondary lamellae and not in the primary filament. Salinity acclimation did not change cell distribution. H. didactylus are capable of swift and significant branchial adjustments to ambient salinity and further studies are needed to evaluate the role of kidney and intestine in the osmoregulatory response. 0

The deep sea hydrothermal vent mussel Bathymodiolus azoricus has been the subject of several studies aimed at understanding the physiological adaptations that vent animals have developed in order to cope with the particular physical and chemical conditions of hydrothermal environments. In spite of reports describing successful procedures to maintain vent mussels under laboratory conditions at atmospheric pressure, few studies have described the mussel s physiological state after a long period in aquaria. In the present study, we investigate changes in mucocytes and hemocytes in Bathymodiolus azoricus over the course of several months after deep-sea retrieval. The visualization of granules of mucopolysaccharide or glycoprotein was made possible through their inherent auto-fluorescent property and the Alcian blue-Periodic Acid Schiff staining method. The density and distribution of droplets of mucus-like granules was observed at the ventral end of lamellae during acclimatization period. The mucus-like granules were greatly reduced after 3 months and nearly absent after 6 months of aquarium conditions. Additionally, we examined the depletion of endosymbiont bacteria from gill tissues, which typically occurs within a few weeks in sea water under laboratory conditions. The physiological state of Bathymodiolus azoricus after 6 months of acclimatization was also examined by means of phagocytosis assays using hemocytes. Hemocytes from mussels held in aquaria up to 6 months were still capable of phagocytosis but to a lesser extent when compared to the number of ingested yeast particles per phagocytic hemocytes from freshly collected vent mussels. We suggest that the changes in gill mucopolysaccharides and hemocyte glycoproteins, the endosymbiont abundance in gill tissues and phagocytosis are useful health criteria to assess long-term maintenance of B. azoricus in aquaria. Furthermore, the laboratory set up to which vent mussels were acclimatized is an applicable system to study physiological reactions such as hemocyte immunocompetence even in the absence of the high hydrostatic pressure found at deep sea vent sites.

Thyroid hormones are involved in many developmental and physiological processes, including osmoregulation. The regulation of the thyroid system by environmental salinity in the euryhaline gilthead seabream (Sparus aurata) is still poorly characterized. To this end seabreams were exposed to four different environmental salinities (5, 15, 40 and 55 ppt) for 14 days, and plasma free thyroid hormones (fT3, ff4), outer ring deiodination and Na+/K+ -ATPase activities in gills and kidney, as well as other osmoregulatory and metabolic parameters were measured. Low salinity conditions (5 ppt) elicited a significant increase in fT3 (29%) and ff4 (184%) plasma concentrations compared to control animals (acclimated to 40 ppt, natural salinity conditions in the Bay of Cadiz, Spain), while the amount of pituitary thyroid stimulating hormone subunit 13 (tshb) transcript abundance remained unchanged. In addition, plasma fT4 levels were positively correlated to renal and branchial deiodinase type 2 (dio2) mRNA expression. Gill and kidney T4-outer ring deiodination activities correlated positively with dio2 mRNA expression and the highest values were observed in fish acclimated to low salinities (5 and 15 ppt). The high salinity (55 ppt) exposure caused a significant increase in tshb expression (65%), but deiodinase gene expression (diol and dio2) and activity did not change and were similar to controls (40 ppt). In conclusion, acclimation to different salinities led to changes in the peripheral regulation of thyroid hormone metabolism in seabream. Therefore, thyroid hormones are involved in the regulation of ion transport and osmoregulatory physiology in this species. The conclusions derived from this study may also allow aquaculturists to modulate thyroid metabolism in seabream by adjusting culture salinity. (C) 2016 Elsevier Inc. All rights reserved. Science Foundation (FCT) of Portugal [SFRH/BPD/89889/2012, SFRH/BPD/84033/2012] Ministerio de Education y Ciencia, Spain [AGL2007-61211/ACU] Proyecto de Excelencia (Junta de Andalucia) [PO7-RNM-02843] Socrates/Erasmus Grant from the European Union info:eu-repo/semantics/acceptedVersion University of Cadiz [UCA 2009-074-FPI] FEDER, Spain [AGL2007-61211/ACU]

Metabolic programming refers to the induction, deletion, or impaired development of a somatic structure or "setting" of a physiological system by an early life stimulus operated at a critical period during development. Ghrelin is the only known orexigenic gut hormone, is an acylated peptide that acts as an endogenous ligand specific for growth-hormone secretagogue-receptor. The aim of the present work was to evaluate if an in ovo ghrelin administration could positively influence the zebrafish performance in the long-term and to gain insight on the mechanisms associated to ghrelin regulation of food intake during the larval phase. Food intake, growth potential, protein metabolism, expression of target genes involved in ghrelin, feeding behaviour regulation and locomotor activity were assessed in zebrafish (Danio rerio) larvae at 25 days post-fertilization. Elevated levels of acylated ghrelin in zebrafish eggs did not result in increased growth or food intake. Differences in mRNA expression between larvae fasted for 16 h before and 1 h after feeding were found for igf1ra, gh1 and pomca. Moreover, ghrelin treated larvae showed higher swimming activity, indicating that the peptide may have an important role on foraging activity. The present study addressed for the first time the effects of an early stimulus of ghrelin during the embryonic stage of zebrafish, however, further studies are needed to clarify the metabolic pathways affected by the early stimulus as well as focus on the effects on metabolic regulation of energy balance through lipid and carbohydrate metabolism. FCT/MCTES (Portugal)Portuguese Foundation for Science and Technology [PTDC/CVT/102481/2008, UID/Multi/04326/2013] Foundation for Science and Technology of Portugal (FCT)Portuguese Foundation for Science and Technology FCT - European Social Fund [IF/00482/2014/CP1217/CT0005] Operational Programme Human Potential