Crecimiento en peces teleósteos

El crecimiento en los peces teleósteos, al igual que ocurre en otros grupos de animales, es el resultado de un complejo proceso en el que se ven implicados diversos factores (ambientales, endocrinos, nutricionales y genéticos). Dentro de los factores endocrinos, existen diversos ejes que intervienen en el proceso de crecimiento. Entre estos ejes, el más importante es el eje somatotrópico, que incluye la hormona de crecimiento (GH), las somatomedinas (IGFI y II), los receptores de estas hormonas, así como las proteínas de unión a la IGF (IGFBP). Sin embargo, otros ejes, tales como el eje hipotálamo-hipofisario-tiroideo (con las hormonas tiroideas T3 y T4 como productos finales), así como el eje hipotálamo-hipofisario-interrenal (con el cortisol como producto final), también juegan un importante parel en el control endocrino del crecimiento. Dentro de los factores ambientales se pueden distinguir dos tipos: a) factores determinantes (temperatura, salinidad, fotoperíodo) que influyen directamente sobre el crecimiento aumentándolo o disminuyéndolo, y b) factores limitantes para los cuáles existe un determinado umbral (NH4+ u oxígeno disuelto) o un margen de tolerancia específico (pH). Entre los factores ambientales, la salinidad es un factor específico del medio acuático y que, por tanto, constituye una variable susceptible de ser modulada en el sector acuícola. Las especies eurihalinas cultivadas (dorada, lenguado, lubina) pueden hacer frente a los cambios en la salinidad ambiental gracias a la actividad de su sistema osmorregulador. Sin embargo, estos procesos osmorreguladores requieren mucha energía y aquellas salinidades ambientales que disminuyan las necesidades energéticas derivadas de los procesos osmorreguladores podrían salvar energía y ayudar a maximizar el crecimiento. En la práctica acuícola, el principal objetivo es la perfecta adaptación del animal a las condiciones de cultivo. Esta adaptación permitirá el mantenimiento en cautividad, crecimiento y reproducción de la especie. Sin embargo, los posibles agentes estresantes en el cultivo de la especie son múltiples y de variado origen (alimentación deficiente, alta densidad de cultivo, baja oxigenación del agua, condiciones físico-químicas del agua no óptima, fotoperiodo y/o termoperiodo no adecuado, vibraciones y ruidos, etc). De este modo, la existencia de una situación de estrés crónico en el cultivo originará una activación del sistema de estrés con altos niveles de cortisol mantenidos durante tiempo (estrés crónico). Bajo estas circunstancias, el cortisol afecta negativamente al crecimiento, pues activa los procesos catabólicos en el teleósteoUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Cultivo de especies de interés comercial en diferentes salinidades ambientales: dorada, corvina y pargo como ejemplos

El estrés, y en particular el estrés osmótico debido a la concentración salina del agua, es un factor muy relevante para la producción en acuicultura. En los teleósteos marinos cultivados, la exposición a un medio hiperosmótico impone en el animal la necesidad de osmorregular, lo cual implica un gasto energético importante. Este coste energético va en detrimento de la tasa de crecimiento de los peces, y por tanto de la productividad de la explotación acuícola. En la bahía de Cádiz existe una consolidada actividad de acuicultura, con un importante impacto económico en la región. Por ello, la optimización de la producción piscícola es de vital importancia. Una de los aspectos a considerar es el impacto de las variables ambientales sobre el cultivo, siendo de particular relevancia la temperatura, el fotoperiodo y la salinidad. En la facultad de Ciencias del Mar existe un centro de cría de especies de interés en acuicultura, e instalaciones adecuadas para la experimentación. Así, experimentos llevados a cabo con dorada y lenguado han permitido establecer que la salinidad del agua es un factor crítico para el crecimiento de los peces cultivados. Además, la salinidad óptima para el cultivo resultó ser diferente para cada especie, y por tanto debe ser optimizada de manera individual. Esto demuestra el coste energético que supone la osmorregulación en los peces, lo cual repercute en su crecimiento.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Aflatoxicosis Dysregulates the Physiological Responses to Crowding Densities in the Marine Teleost Gilthead Seabream (Sparus aurata)

A fungal toxin, aflatoxin B1 (AFB1), undermines growth and stress axes of gilthead seabream (Sparus aurata) with depletion of somatic carbohydrate and lipid reservoirs. The present study assessed the physiological consequences of high stocking density versus low stocking density in seabream juveniles, which had previously been fed with AFB1 supplementation. These stressors are likely to converge by inferring animal welfare and economic profitability in the food animal industry. Interestingly, AFB1 seems to cause physiological and molecular dysfunction in response to overcrowding densities. Our results might be relevant to elucidate a potential risk for fish farming that is often overlooked. Several studies in fish have shown that aflatoxin B1 (AFB1) causes a disparity of species-dependent physiological disorders without compromising survival. We studied the effect of dietary administration of AFB1 (2 mg AFB1 kg(-1) diet) in gilthead seabream (Sparus aurata) juveniles in combination with a challenge by stocking density (4 vs. 40 g L-1). The experimental period duration was ten days, and the diet with AFB1 was administered to the fish for 85 days prior to the stocking density challenge. Our results indicated an alteration in the carbohydrate and lipid metabolites mobilization in the AFB1 fed group, which was intensified at high stocking density (HSD). The CT group at HSD increased plasma cortisol levels, as expected, whereas the AFB1-HSD group did not. The star mRNA expression, an enzyme involved in cortisol synthesis in the head kidney, presented a ninefold increase in the AFB1 group at low stocking density (LSD) compared to the CT-LSD group. Adenohypophyseal gh mRNA expression increased in the AFB1-HSD but not in the CT-HSD group. Overall, these results confirmed that chronic AFB1 dietary exposure alters the adequate endocrinological physiological cascade response in S. aurata, compromising the expected stress response to an additional stressor, such as overcrowding

Metabolic and Stress Responses in Senegalese Soles (Solea senegalensis Kaup) Fed Tryptophan Supplements: E ects of Concentration and Feeding Period

The objective of this study was to assess the impact of di erent dietary Trp concentrations on the stress and metabolism response of juvenile Senegalese soles (Solea senegalensis). Fish (38.1 1.9 g) were fed di erent Trp-enriched feeds (0%, 1% and 2% Trp added) for two and eight days, and later exposed to air stress for three min. Samples were taken pre- and 1 h post-stress (condition). Plasma cortisol, lactate, glucose and proteins were significantly a ected by the sampling time, showing higher values at 1 h post-stress. Trp concentration in food also had significant e ects on lactate and glucose levels. However, the feeding period did not a ect these parameters. Post-stress values were higher than in the pre-stress condition for every plasma parameter, except for lactate in two days and 1% Trp treatment. Nevertheless, cortisol, glucose and lactate did not vary significantly between pre- and post-stress samplings in fish fed the 1% Trp-enriched diet for two days. The lack of variability in cortisol response was also due to the high pre-stress value, significantly superior to pre-stress control. The exposure time to Trp feeding did not significantly a ect any enzyme activity; however, Trp added and condition influenced protein-related enzyme activities. In spite of decreasing stress markers, Trp-enriched diets altered the protein metabolism

Cortisol and Dexamethasone Mediate Glucocorticoid Actions in the Lesser Spotted Catshark (Scyliorhinus canicula)

Corticosteroids are hormones produced in vertebrates exerting gluco- and mineralocorticoid actions (GC and MC) mediated by specific receptors (GR and MR, respectively). In elasmobranchs, the major circulating corticosteroid is the 1 -hydroxycorticosterone (1 -OHB). This hormone acts as a MC, but to date its role as a GC has not been established. As there is no 1 -OHB standard available, here we employed a set of in vivo and ex vivo approaches to test GC actions of other corticosteroids in the lesser spotted catshark (Scyliorhinus canicula). Dexamethasone (DEX, a synthetic corticosteroid) slow-release implants decreased plasma 1 -OHB levels after 7 days, and modified carbohydrates metabolism in liver and white muscle (energy stores and metabolic enzymes). In addition, ex vivo culture of liver and white muscle explants confirmed GC actions of corticosteroids not naturally present in sharks (cortisol and DEX) by increasing glucose secretion from these tissues. Dose–response curves induced by cortisol and DEX, altogether with the use of specific GR inhibitor mifepristone, confirmed the involvement of GR mediating glucose secretion. This study highlights the influence of corticosteroids in the glucose balance of S. canicula, though the role of 1 -OHB as a GC hormone in sharks should be further confirmed

New Perspectives Related to the Bioluminescent System in Dinoflagellates: Pyrocystis lunula, a Case Study

Pyrocystis lunula is considered a model organism due to its bioluminescence capacity linked to circadian rhythms. The mechanisms underlying the bioluminescent phenomenon have been well characterized in dinoflagellates; however, there are still some aspects that remain an enigma. Such is the case of the presence and diversity of the luciferin-binding protein (LBP), as well as the synthesis process of luciferin. Here we carry out a review of the literature in relation to the molecular players responsible for bioluminescence in dinoflagellates, with particular interest in P. lunula. We also carried out a phylogenetic analysis of the conservation of protein sequence, structure and evolutionary pattern of these key players. The basic structure of the luciferase (LCF) is quite conserved among the sequences reported to date for dinoflagellate species, but not in the case of the LBP, which has proven to be more variable in terms of sequence and structure. In the case of luciferin, its synthesis has been shown to be complex process with more than one metabolic pathway involved. The glutathione S-transferase (GST) and the P630 or blue compound, seem to be involved in this process. In the same way, various hypotheses regarding the role of bioluminescence in dinoflagellates are exposed

Avances en Endocrinología Comparada, Vol. IV

Esta monografía constituye el cuarto volumen de la serie "Avances en Endocrinología Comparada", cuyo objetivo principal es proporcionar a la comunidad científica una visión actualizada y rigurosa de las actividades investigadoras que se desarrollan en esta disciplina científica en España y Portugal. Las contribuciones que se presentan en esta obra reflejan, en gran medida, los resultados expuestos por los investigadores participantes en el 6º Congreso de la Asociación Ibérica de Endocrinología Comparada (AIEC), celebrado en Cádiz en septiembre de 2007. Estas contribuciones, cuyo hilo conductor es el interés por los estudios endocrinológicos utilizando distintos modelos animales, han abordado temáticas de Biología y Genética del desarrollo del sistema endocrino, neuroendocrinología, control endocrino de diversos procesos fisiológicos (reproducción, crecimiento, metabolismo, balance hidromineral, estrés, respuesta inmune, etc.), acciones ambientales y antropogénicas sobre el sistema endocrino, nuevas tecnologías para el estudio del sistema endocrino y aplicaciones prácticas de la Endocrinología

Acute-Stress Biomarkers in Three Octopodidae Species After Bottom Trawling

Several Octopodidae species have a great potential for the diversification of worldwide aquaculture. Unfortunately, the lack of stress-related biomarkers in this taxon results an obstacle for its maintenance in conditions where animal welfare is of paramount relevance. In this study, we made a first approach to uncover physiological responses related to fishing capture in Eledone moschata, Eledone cirrhosa, and Octopus vulgaris. Captured octopus from all three species were individually maintained in an aquaculture system onboard of oceanographic vessel in south-western waters of Europe. Haemolymph plasma and muscle were collected in animals at the moment of capture, and recovery was evaluated along a time-course of 48 h in Eledone spp., and 24 h for O. vulgaris. Survival rates of these species captured in spring and autumn were evaluated. Physiological parameters such as plasma pH, total CO2, peroxidase activity, lysozyme, hemocyanin, proteases, pro-phenoloxidase, anti-proteases, free amino acids, lactate and glucose levels, as well as muscle water percentage, free amino acids, lactate, glycogen and glucose values were analyzed. The immune system appears to be compromised in these species due to capture processes, while energy metabolites were mobilized to face the acute-stress situation, but recovery of all described parameters occurs within the first 24 h after capture. Moreover, this situation exerts hydric balance changes, as observed in the muscle water, being these responses depending on the species assessed. In conclusion, three Octopodidae species from south-western waters of Europe have been evaluated for stress-related biomarkers resulting in differentiated mechanisms between species. This study may pave the way to further study the physiology of stress in adult octopuses and develop new methodologies for their growth in aquaculture conditions

Essential Oils as Stress-Reducing Agents for Fish Aquaculture: A Review

In fish, stressful events initiate a hormone cascade along the hypothalamus-pituitaryinterrenal and hypothalamus-sympathetic-chromaffin (HSC) axis to evoke several physiological reactions in order to orchestrate and maintain homeostasis. Several biotic and abiotic factors, as well as aquaculture procedures (handling, transport, or stocking density), activated stress system inducing negative effects on different physiological processes in fish (growth, reproduction, and immunity). In order to reduce these consequences, the use of essential oils (EOs) derived from plants has been the focus of aquaculture studies due to their diverse properties (e.g., anesthetic, antioxidant, and antimicrobial), which have been shown to reduce biochemical and endocrine alterations and, consequently, to improve the welfare status. Recently, several studies have shown that biogenic compounds isolated from different EOs present excellent biological activities, as well as the nanoencapsulated form of these EOs may potentiate their effects. Overall, EOs presented less side effects than synthetic compounds, but their stress-reducing efficacy is related to their chemical composition, concentration or chemotype used. In addition, their species-specific actions must be clearly established since they can act as stressors by themselves if their concentrations and chemotypes used are not suitable. For this reason, it is necessary to assess the effect of these natural compound mixtures in different fish species, from marine to freshwater, in order to find the ideal concentration range and the way for their administration to obtain the desired biological activity, without any undesired side effects. In this review, the main findings regarding the use of different EOs as stress reducers will be presented to highlight the most important issues related to their use to improve fish welfare in aquaculture

Antimicrobial and Toxic Activity of Citronella Essential Oil (Cymbopogon nardus), and Its Effect on the Growth and Metabolism of Gilthead Seabream (Sparus aurata L.)

Aquaculture procedures usually induce stress that affects the physiological status of fish. For this reason, the inclusion of additives in fish feeds to palliate stress might be a good alternative. This study aimed to assess the antimicrobial activity of citronella (Cymbopogon nardus) essential oil (CEO) against bacterial pathogens and to determine its dietary impact on the growth performance of Sparus aurata. In vitro tests confirmed that CEO possesses antimicrobial activity against several fish-specific pathogens. For the in vivo tests, three experimental groups were fed for 60 days with different concentrations of CEO: CTRL (0 mL kg(-1) fish feed); CEO1 (1 mL kg(-1) fish feed); and CEO2 (2 mL kg(-1) fish feed). At the end of the experiment, the physiological status was characterized. Subsequently, the specimens of the CTRL and CEO2 groups were subjected to a challenge with an injection of Poly I:C for immune stimulation. Although S. aurata individuals tolerated CEO inclusion without compromising growth performance, it significantly reduced glycogen in the CEO2 group, concomitant to an increment of total peripheral leucocytes. Moreover, different hematological profiles' responsive patterns against an inflammatory stimulus were observed. In conclusion, our results suggest that the use of CEO as a fish feed additive can prevent bacterial outbreaks and improve potential in vivo disease resistance in S. aurata without negatively affecting growth