Suchergebnisse

Understanding the daily digestive function could lead to more efficient feeding practices in the farmed fish species. In this work, the effect of several daily feeding protocols was assessed on the daily expression of the genes related to the circadian system (arntl1, clock, per1, and cry1), appetite (cck), nutrients hydrolysis (try1, ctrb1, pga, atp4a, cel, and amy2a), peptides transport (slc15a1), pH, and activity of key digestive (trypsin, chymotrypsin, amylase, 4C- and 7C-like lipases) and absorptive (alkaline phosphatase) enzymes in the gastrointestinal tract (GIT) of Senegalese sole (Solea senegalensis) juveniles. Some of the tested feeding protocols demonstrated a significant influence on the entrainment of the peripheral oscillator. The synchrony of slc15a1 and some digestive proenzymes with per1 in some of the experimental treatments could underline the role of clock genes in the regulation of these biological functions. Unlike gene expression of the digestive proenzymes wherein feeding protocol occasionally affected the temporal organization, the influence of this factor was determinant on the daily average production and/or circadian pattern of their activities. Daily pH was maintained at approximately neutral levels in all the GIT segments, and no pepsin activity was detected. Fish fed a single diurnal meal showed the lowest activity for all the studied enzymes, except for amylase, suggesting an insufficient utilization of the ingested nutrients. Higher amylase activity in this group, on the other hand, implies the possible activation of alternative compensatory metabolic pathways. Overall, our results pointed to the suitability of higher feeding frequencies, especially during dark hours, for the aquaculture production of this species. ; This research was funded by the Spanish Ministry of Economic Affairs and Competitiveness (MINECO) by projects EFISHDIGEST (AGL2014-52888-R) with FEDER/ERDF contribution granted to MY and WISEFEED funded by the European Union's H2020 Program (Marie Skłodowska-Curie Grant No. 691150). NG was supported by a doctoral fellowship (BES-2015-071662) from MINECO (Spain).

Trabajo presentado en Aquaculture Europe 19 (Our future, growing from water), celebrado en Berlín del 7 al 10 de octubre de 2019. ; Digestion consists of a group of complex processes, involving physical, chemical, and biochemical transformations of the ingested food. All of them are interdependent and finely tuned by a number of molecular, hormonal, and nervous signals, many of which are driven by the circadian system. This system is composed of several interconnected oscillators, for which light-dark and feeding-fasting cycles are the most powerful synchronizers. An increased knowledge of Food Anticipatory Activity (FAA), an out of Food-entrainable oscillators (FEO), may help to optimize the utilization of nutrients by a given species adapting feeding protocols to these internal rhythms. The present work aimed to evaluate the rhythmicity of some of the gastrointestinal tract (GIT) factors that are related to digestive efficiency in gilthead seabream (Sparus aurata) juveniles as well as to determine how these factors are affected by different feeding protocols. ; Grants AGL2014-52888-R from MINECO (Spain) with FEDER/ERDF contribution, and WISEFEED funded by the European Union's H2020 programme (Marie Skłodowska-Curie grant No 691150). NG supported by BES-2015-071662 from MINECO. ; Peer reviewed

Models simulating the in vitro digestive hydrolysis of nutrients by different animal species are frequently used to obtain a better understanding of factors affecting this process. Optimization algorithm of a model may be used to prospect the more favourable combination of selected factors resulting in the higher performance. This study was conducted to determine the combination of factors (pH, enzyme:substrate ratio, and reaction time) leading to highest bioavailability of proteins and carbohydrates in the gilthead seabream gastrointestinal tract. Besides, a novel multi-objective algorithm, desirability function, was introduced for optimization of the digestive hydrolysis of nutrients within the simulated gut of the species, using models based on the Response Surface Methodology. Design of experiment was defined based on the physiology and culture conditions of the species, and in vitro assays were performed in a two-phase (stomach ad intestine) digestion process, using the species-specific enzyme extract. According to results, intestinal phase of digestion makes the major contribution to the total protein hydrolysis, being the efficiency of the process directly correlated to all the three studied factors. In contrast, the efficiency of carbohydrate hydrolysis was directly correlated to the amount of substrate and inversely to the pH, while reaction time did not exert a significant effect. The physiological range of the factors studied in the assays favoured the hydrolysis of proteins over carbohydrates, a similar scenario to that observed in the live fish. Results from the mathematical models and their simultaneous optimization obtained from this work may have practical applications in design of feeds for this species. ; This research was funded by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO) with FEDER/ERDF contribution by project EFISHDIGEST (AGL2014-52888-R) to MY. Additional funding from project WISEFEED funded by the European Union's H2020 programme (Marie Skłodowska-Curie grant No 691150). NG is supported by a grant from MINECO (BES-2015-071662). ; Peer reviewed

The present work uses a novel approach to develop a mathematical model explaining the effect of three main factors - temperature, total reaction time and enzyme:substrate ratio - in the hydrolysis of protein by the intestinal enzymes of the Senegalese sole. The methodology combines a factorial design based in the Response Surface Methodology and in vitro digestibility assays adapted to the physiology and culture conditions of the species. The model revealed that, within the physiological ranges considered in the study, the efficiency of protein hydrolysis by the intestinal enzymes of the sole was linearly correlated to two of the selected factors; directly to incubation time and inversely to the amount of substrate. The effect of temperature was not linear but quadratic, hence showing a maximum at 23 °C. The information obtained can be used as a tool to maximize the biological response under variable conditions and may orientate some on-farm feeding practices. ; This research was funded by the Spanish Ministry of Economic Affairs and Competitiveness (MINECO) by projects EFISHDIGEST (AGL2014-52888-R) with FEDER/ERDF contribution granted to M.Y. and WISEFEED funded by the European Union's H2020 programme (Marie Skłodowska-Curie grant No 691150). Neda Gilannejad was supported by a doctoral fellowship (BES-2015-071662) from MINECO (Spain). ; Peer reviewed

8º Congreso Asociación Ibérica de Endocrinología Comparada (AIEC), Madrid, 5-7 septiembre, 2011. ; Gilthead sea bream (S. aurata) is a eurihaline fish, and therefore presents the capacity to live under different environmental salinities, expending extra energy for maintaining the homeostasis when there are osmotic differences between the internal medium and the external environment. In fish, glucose has a relevant role in osmotic stress, supplying the necessary extra energy to the osmoregulatory organs. This metabolite is a hydrophilic molecule that needs a specific transporter (GLUT) to cross plasma membrane. Several members of the GLUT family have been cloned in various fish species, but not in S. aurata. In this study we have cloned the S. aurata GLUT1 (saGLUT1). The cDNA is composed by 4483 bp, with a 5¿UTR of 173 bp, ORF 1476 bp and 3¿UTR which has 2616 bp, presenting high similarity to GLUT1 in other fish species (between 79 to 95 % identity). In addition, saGLUT1 mRNA expression changes in gills, kidney, liver and brain were determined by real time PCR analysis in specimens of 100-150 g body weight, acclimated to four different salinities (5, 12, 40 and 55 ppt) during 15 days. The major levels of expression were found in brain and gills (5000 and 8000 copies/10 ng RNA). Statistical differences in gills (highest expression at 40 ppt) and kidney (highest expression at 5 ppt) were detected, without any significant changes in brain and liver. Our results show that saGLUT1 mRNA expression is regulated in osmoregulatory organs in response to different environmental salinities ; CB-A is supported by a postdoctoral fellowship "Becas Chile" from Chile Government. JAM-S is supported by a Ph.D. fellowship (FPU) from (he Spanish Ministry of Education. ; Peer Reviewed

Trabajo presentado en el XIII Congreso de la Asociación Ibérica de Endocrinología Comparada, celebrado los días 16 y 17 de septiembre de 2021 ; Corticosteroids control inter alia, metabolism, immunology, osmoregulation, and stress responses. In the present work, we examined the different physiological and molecular responses evoked in the gilthead seabream acclimated to seawater (SW, 38 ppt) after chronic oral administration for 30 days of cortisol (F; 400 mg/kg fish feed) and the synthetic glucocorticoid dexamethasone (DEX; 300 mg/kg fish feed), prior- and post-hypersaline seawater (HSW, 60 ppt) direct transfer for 3 days. After the feeding trial, plasma cortisol levels showed the following pattern: CT > F > DEX. HSW transfer significantly enhanced plasma cortisol levels in the CT group, whereas F and DEX groups showed about half of these values. Na+/K+-ATPase (NKA) activity increased dramatically in the DEX group prior to HSW transfer. Surprisingly gill NKA activity levels in this tissue were recovered to the initial lowest levels for all the groups. Plasma and intestinal fluid osmolalities enhanced significantly after HSW transfer in the DEX group. Intestinal short circuit-current (Isc) showed a more anion absorptive capacity in the posterior intestine (PI) than the anterior. Moreover, F treatment significantly increased this anion absorptive capacity in the PI after HSW transference. Surprisingly HSW significantly decreased the anion absorptive capacity in all intestinal regions, specifically in the PI, indicating the appearance and/ or switch to secretory mechanisms in the intestine to counteract hypersalinity. Furthermore, molecular hypophyseal markers such as the pomcb and the gh were significantly altered/modulated by both pharmacological treatments and HSW challenge. ; This work was funded by Agencia Estatal de Investigación (Ministerio de Ciencia e Investigación, Spanish Government) (PID2020-117557RB-C22). A. Barany was supported by the University of Cadiz Ph.D. scholarship (UCA/REC01VI/2017).

Aflatoxin B1 (AFB1) is a mycotoxin often present in food. This study aimed to understand the physiological effects of AFB1 on the seabream (Sparus aurata) gastrointestinal system. In a first in vitro approach, we investigated ion transport using the short-circuit current (Isc) technique in Ussing chambers in the anterior intestine (AI). Application of apical/luminal AFB1 concentrations of 8 and 16 μM to healthy tissues was without effect on tissue transepithelial electrical resistance (TER), and apparent tissue permeability (Papp) was measured using fluorescein FITC (4 kD). However, it resulted in dose-related effects on Isc. In a second approach, seabream juveniles fed with different AFB1 concentrations (1 and 2 mg AFB1 kg fish feed) for 85 days showed significantly reduced gill Na/K-ATPase (NKA) and H-ATPase (HA) activities in the posterior intestine (PI). Moreover, dietary AFB1 modified Isc in the AI and PI, significantly affecting TER in the AI. To understand this effect on TER, we analyzed the expression of nine claudins and three occludins as markers of intestinal architecture and permeability using qPCR. Around 80% of the genes presented significantly different relative mRNA expression between AI and PI and had concomitant sensitivity to dietary AFB1. Based on the results of our in vitro, in vivo, and molecular approaches, we conclude that the effects of dietary AFB1 in the gastrointestinal system are at the base of the previously reported growth impairment caused by AFB1 in fish. ; This work was funded by the Spanish Ministry of Economy and Business-MINECO (AGL2016-76069-C2-1-R) awarded to JM. The authors (AB and JM) belong to the Fish Welfare and Stress Network (AGL2016-81808-REDT), supported by the Agencia Estatal de Investigación (MINECO, Spanish Government). AB was supported by the University of Cadiz Ph.D. scholarship (PIF UCA/REC02VIT/2014). CCMar is supported by national funds from the Portuguese Foundation for Science and Technology (FCT) through project UIDB/04326/2020.

Trabajo presentado en el XII Conference of the Iberian Association for Comparative Endocrinology (AIEC), celebrado en Faro (Portugal), del 26 al 28 de septiembre de 2019. ; Cortisol is the most important hormone involved in the regulation of neuroendocrine stress response in teleosts. Effects of this hormone are mediated through its intracellular receptors, although membrane components are also involved, with unclear roles during the stress response. In this work, the contribution of membrane-initiated cortisol actions on stress-related parameters and metabolism-related genes in gilthead sea bream (Sparus aurata) were evaluated. Two in vivo experiments were performed. In the first, fish were administered with vehicle, BSA, cortisol and cortisol-BSA (membrane impermeable analogue) dissolved in saline (PBS 1X). In the second, the same treatments were replicated but using coconut oil as a vehicle. Fish were sampled after one and six hours (first experiment) and after three days (second experiment). Plasma cortisol, glucose and lactate levels were measured, and hepatic transcript levels of key genes involved in glucose metabolism, like glucose-6-phosphatase (g6pc), phosphoglycerate mutase 1 (pgam1), among others, were also analyzed. Fish implanted with each version of cortisol in both in vivo experiments reached plasma levels typically observed under an acute stress in S. aurata. Cortisol and cortisol-BSA increased glucose and lactate plasma levels after six hours of treatment. However, cortisol, but not cortisol-BSA, maintained increased plasma glucose levels after three days of treatment. Analysis by qPCR showed that expression of g6pc increased after one hour of cortisol and cortisol-BSA administration. However, cortisol, but not cortisol-BSA, maintained the g6pc up-regulation after three days. Our results suggested that membrane-initiated cortisol actions contributed to the regulation of early metabolic adaptations in S. aurata submitted to an emulated acute stress situation. ; This work was funded by Spanish Ministry of Science, Innovation and Universities - MICINN (AGL2016-76069-C2-1-R) awarded to JMM. The authors belong to the Fish Welfare and Stress Network (AGL2016-81808-REDT), supported by the Agencia Estatal de Investigación (MICINN, Spanish Government). ; Peer reviewed

Osmotic costs in teleosts are highly variable, reaching up to 50% of energy expenditure in some. In several species, environmental salinities close to the isosmotic point (~15 psu) minimize energy demand for osmoregulation while enhancing growth. The present study aimed to characterize the physiological status related to osmoregulation in early juveniles of the greater amberjack, Seriola dumerili, acclimated to three salinities (15, 22, and 36 psu). Our results indicate that plasma metabolic substrates were enhanced at the lower salinities, whereas hepatic carbohydrate and energetic lipid substrates decreased. Moreover, osmoregulatory parameters, such as osmolality, muscle water content, gill and intestine Na-K-ATPase activities, suggested a great osmoregulatory capacity in this species. Remarkably, electrophysiological parameters, such as short-circuit current (Isc) and transepithelial electric resistance (TER), were enhanced significantly at the posterior intestine. Concomitantly, Isc and TER anterior-to-posterior intestine differences were intensified with increasing environmental salinity. Furthermore, the expression of several adeno-hypophyseal genes was assessed. Expression of prl showed an inverse linear relationship with increasing environmental salinity, while gh mRNA enhanced significantly in the 22 psu-acclimated groups. Overall, these results could explain the better growth observed in S. dumerili juveniles kept at salinities close to isosmotic rather than in seawater. ; This research was funded by Project "Diversificación de la Acuicultura Española mediante la optimización del cultivo de Seriola dumerili" JACUMAR 2016 (MAPAMA) and Fondo Europeo Marítimo y de Pesca (FEMP). The authors (A.B. and J.M.M.) belong to the FishWelfare and Stress Network (AGL2016-81808-REDT), supported by the Agencia Estatal de Investigación (MINECO, Spanish Government).

High rearing densities are typical conditions of both inland and onshore intensive aquaculture units. Despite obvious drawbacks, this strategy is nonetheless used to increase production profits. Such conditions inflict stress on fish, reducing their ability to cope with disease, bringing producers to adopt therapeutic strategies. In an attempt to overcome deleterious effects of chronic stress, Senegalese sole, Solea senegalensis, held at low (LD) or high density (HD) were fed tryptophan-supplemented diets with final tryptophan content at two (TRP2) or four times (TRP4) the requirement level, as well as a control and non-supplemented diet (CTRL) for 38 days. Fish were sampled at the end of the feeding trial for evaluation of their immune status, and mortalities were recorded following intra-peritoneal infection with Photobacterium damselae subsp. piscicida. Blood was collected for analysis of the hematological profile and innate immune parameters in plasma. Pituitary and hypothalamus were sampled for the assessment of neuro-endocrine-related gene expression. During the feeding trial, fish fed TRP4 and held at LD conditions presented higher mortalities, whereas fish kept at HD seemed to benefit from this dietary treatment, as disease resistance increased over that of CTRL-fed fish. In accordance, cortisol level tended to be higher in fish fed both supplemented diets at LD compared to fish fed CTRL, but was lower in fish fed TRP4 than in those fed TRP2 under HD condition. Together with lower mRNA levels of proopiomelanocortin observed with both supplementation levels, these results suggest that higher levels of tryptophan might counteract stress-induced cortisol production, thereby rendering fish better prepared to cope with disease. Data regarding sole immune status showed no clear effects of tryptophan on leucocyte numbers, but TRP4-fed fish displayed inhibited alternative complement activity (ACH50) when held at LD, as opposed to their HD counterparts whose ACH50 was higher than that of CTRL-fed fish. In conclusion, while dietary tryptophan supplementation might have harmful effects in control fish, it might prove to be a promising strategy to overcome chronic stress-induced disease susceptibility in farmed Senegalese sole. ; This work was partially supported by the Strategic Funding UID/Multi/04423/2019 and projects IF/00197/2015 and PTDC/CVT-CVT/32349/2017 through national funds provided by FCT – Foundation for Science and Technology and European Regional Development Fund (ERDF), in the framework of the programs COMPETE 2020, CRESC Algarve 2020, and PORTUGAL 2020. MM and BC were supported by FCT (SFRH/BD/108243/2015 and IF/00197/2015, respectively). This study was also partially supported by the grant AGL2016-76069-C2-1-R (Ministerio de Economía y Competitividad, Spain) awarded to JMM. JM-S and JMM belong to the Fish Welfare and Stress Network (AGL2016-81808-REDT), supported by the Agencia Estatal de Investigación (MINECO, Spanish Government).

Transport processes between aquaculture facilities activate the stress response in fish. To deal with these situations, the hypothalamic-pituitary-interrenal (HPI) axis releases cortisol, leading to an increase in circulating energy resources to restore homeostasis. However, if the allostatic load generated exceeds fish tolerance limits, stress-related responses will compromise health and welfare of the animals. In this context, anesthetics have arisen as potential agents aiming to reduce negative effects of stress response. Here we assessed the effects of a sedative dose of clove oil (CO) and MS-222 on hallmarks involved in HPI axis regulation and energy management after simulated transport, and further recovery, in gilthead seabream (Sparus aurata L.) juveniles. Fish were placed in a mobile setup of water tanks where transport conditions were simulated for 6 h. Sedation doses of either CO (2.5 mg L−1) or MS-222 (5 mg L−1) were added in the water tanks. A control group without anesthetics was also included in the setup. Half of the animals (n = 12 per group) were sampled immediately after transport, while remaining animals were allowed to recover for 18 h in clean water tanks and then sampled. Our results showed that the HPI axis response was modified at peripheral level, with differences depending on the anesthetic employed. Head kidney gene-expressions related to cortisol production (star and cyp11b1) matched concomitantly with increased plasma cortisol levels immediately after transport in CO-sedated fish, but these levels remained constant in MS-222-sedated fish. Differential changes in the energy management of carbohydrates, lipids and amino acids, depending on the anesthetic employed, were also observed. The use of CO stimulated amino acids catabolism, while MS-222-sedated fish tended to consume liver glycogen and mobilize triglycerides. Further studies, including alternative doses of both anestethics, as well as the assessment of time-course HPI activation and longer recovery periods, are necessary to better understand if the use of clove oil and MS-222 is beneficial for S. aurata under these circumstances. ; This work was funded by Spanish Ministry of Science, Innovation and Universities - MICINN (AGL2013-48835-C2-1-R and AGL2016-76069-C2-1-R) awarded to JM. IJ-C is currently supported by a contract of Trainee Predoctoral Research Staff from the University of Cádiz (PIF UCA/REC02VIT/2014; 2018-011/PU/AY.PUENTE/CD). The authors (IJ-C, IR-J, JM-S, and JM) belong to the Fish Welfare and Stress Network (AGL2016-81808-REDT), supported by the Agencia Estatal de Investigación (MICINN, Spanish Government).

Cortisol is the main glucocorticoid hormone promoting compensatory metabolic responses of stress in teleosts. This hormone acts through genomic and membrane-initiated actions to exert its functions inside the cell. Experimental approaches, using exogenous cortisol administration, confirm the role of this hormone during short (minutes to hours)- and long-term (days to weeks) responses to stress. The role of membrane-initiated cortisol signaling during long-term responses has been recently explored. In this study, Sparus aurata were intraperitoneally injected with coconut oil alone or coconut oil containing cortisol, cortisol-BSA, or BSA. After 3 days of treatment, plasma, liver, and skeletal muscle were extracted. Plasma cortisol, as well as metabolic indicators in the plasma and tissues collected, and metabolism-related gene expression, were measured. Our results showed that artificially increased plasma cortisol levels in S. aurata enhanced plasma glucose and triacylglycerols values as well as hepatic substrate energy mobilization. Additionally, cortisol stimulated hepatic carbohydrates metabolism, as seen by the increased expression of metabolism-related genes. All of these responses, observed in cortisol-administered fish, were not detected by replicating the same protocol and instead using cortisol-BSA, which exclusively induces membrane-initiated effects. Therefore, we suggest that after three days of cortisol administration, only genomic actions are involved in the metabolic responses in S. aurata. ; This work was funded by Spanish Ministry of Science and Innovation-MICINN (PID2020117557RB-C22) awarded to JMM; Fondo de Financiamiento de Centros de Investigacion en Areas Prioritarias (FONDAP) Grant INCAR 15110027; Fondo Nacional de Desarrollo Cientifico y Tecnologico (FONDECYT) Grant 1201498 (to Juan Antonio Valdes), and ANID FONDECYT Postdoctorado [grant number 3210050] awarded to Jorge E. Aedo. The authors (I.R, G.M, and J.M.M) belong to the FishWelfare and Stress Network (AGL2016-81808-REDT), supported by the Agencia Estatal de Investigacion (MICINN, Spanish Government).

Osmotic costs in teleosts are highly variable, reaching up to 50% of energy expenditure in some. In several species, environmental salinities close to the isosmotic point (similar to 15 psu) minimize energy demand for osmoregulation while enhancing growth. The present study aimed to characterize the physiological status related to osmoregulation in early juveniles of the greater amberjack, Seriola dumerili, acclimated to three salinities (15, 22, and 36 psu). Our results indicate that plasma metabolic substrates were enhanced at the lower salinities, whereas hepatic carbohydrate and energetic lipid substrates decreased. Moreover, osmoregulatory parameters, such as osmolality, muscle water content, gill and intestine Na+-K+-ATPase activities, suggested a great osmoregulatory capacity in this species. Remarkably, electrophysiological parameters, such as short-circuit current (Isc) and transepithelial electric resistance (TER), were enhanced significantly at the posterior intestine. Concomitantly, Isc and TER anterior-to-posterior intestine differences were intensified with increasing environmental salinity. Furthermore, the expression of several adeno-hypophyseal genes was assessed. Expression of prl showed an inverse linear relationship with increasing environmental salinity, while gh mRNA enhanced significantly in the 22 psu-acclimated groups. Overall, these results could explain the better growth observed in S. dumerili juveniles kept at salinities close to isosmotic rather than in seawater. ; This research was funded by Project "Diversificacion de la Acuicultura Espanola mediante la optimizacion del cultivo de Seriola dumerili" JACUMAR 2016 (MAPAMA) and Fondo Europeo Maritimo y de Pesca (FEMP). The authors (A.B. and J.M.M.) belong to the FishWelfare and Stress Network (AGL2016-81808-REDT), supported by the Agencia Estatal de Investigacion (MINECO, Spanish Government).

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, fT4), 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 fT4 (184%) plasma concentrations compared to control animals (acclimated to 40 ppt, natural salinity conditions in the Bay of Cádiz, Spain), while the amount of pituitary thyroid stimulating hormone subunit β (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 (dio1 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. ; This work was partially supported by a Socrates/Erasmus Grant from the European Union and a Ph.D. scholarship from the University of Cadiz (UCA 2009-074-FPI) to I. R-J. It has been also supported by grants AGL2007-61211/ACU (Ministerio de Educación y Ciencia and FEDER, Spain) and Proyecto de Excelencia PO7-RNM-02843 (Junta de Andalucía) to J.M.M. BL (SFRH/BPD/89889/2012) and PISP (SFRH/BPD/84033/2012) were supported by the Science Foundation (FCT) of Portugal. ; Peer reviewed