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The present study aimed to assess the effects of increased availability of dietary amino acids (AA) on brain monoamine neurotransmitters and the metabolic processes resulting from stressful situations in fish. Senegalese sole (Solea senegalensis) juveniles (24.2 ± 0.4 g wet mass) were weekly subjected to an acute handling stressor (HDLG) or remained undisturbed (CTL). Additionally, both treatments were fed a control or a high protein (HP) diet (CTL, CTL HP, HDLG and HDLG HP). The HP diet slightly increased the levels of digestible indispensable AA, together with tyrosine and cysteine. Repeated handling induced a stress response after 14 and 28 days in fish held at both HDLG and HDLG HP treatments. While dietary treatment and handling stress activated the serotonergic system at 14 days, these effects were not observed after 28 days. In addition, the HP diet minimized the decrease in plasma indispensable AA due to repeated handling stress after 28 days. It was concluded that HP diet decreased post-stress plasma glucose and lactate levels in HDLG HP specimens only at 14 days of treatment. Moreover, dietary treatment was also effective in stimulating DA synthesis and release, thus dietary phenylalanine supplementation can increase DA biosynthesis in fish.

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Dissertação de mest., Aquacultura e Pescas, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2009 Docosahexaenoic acid (DHA) is an essential fatty acid for marine fish larvae, with effects on growth and larval quality. DHA requirements for Senegalese sole (Solea senegalensis), a species of high commercial interest, are poorly understood. On this thesis a dose–response design in conjunction with a methodology based on tube feeding of 14C-[DHA], was employed in order to determine the dietary DHA requirements for Senegalese sole post-larvae. The effect of dietary DHA was examined on growth, survival, pigmentation and Artemia intake (at low light conditions). From 22 to 35 days after hatching (DAH) - pre-weaning period - post-larvae were fed frozen Artemia that had been enriched using one of four experimental emulsions containing four graduated concentrations of DHA. Final levels of DHA in the enriched Artemia metanauplii were 0.0 mg g-1DW (DHA-0), 5.1 mg g-1DW (DHA-5), 14.1 mg g-1DW (DHA-14) and 30.2 mg g-1DW (DHA-30). Afterwards and during the weaning period (41 to 61 DAH) all post-larvae were fed with a same moist feed. Significant differences in dry weight (DW) were found at the end of the pre-weaning period. Treatment DHA-0, induced a higher larval growth (2.84±1.04 mgDW) than treatment DHA-5 (2.38±0.74 mgDW). Light intensity influenced both final DW and RGR and there was a positive correlation for a higher growth (DW and RGR) as the light intensity increased. On weaning period treatments DHA-0 and DHA-30 showed significant higher DW and total length values than those presented in DHA-5 and DHA-14. On the radiolabelled Artemia intake test, and after 30 min in presence of Artemia (T30), larvae ingested significantly higher amounts than observed at 10 min, and a positive correlation between dietary DHA levels and Artemia fed within the T10 groups was also found. Tube feeding of [1- 14C]DHA resulted in no significant differences for absorption, retention and catabolism between larvae submitted to different experimental treatments. However, a slight tendency for an increase in the percentage of catabolised DHA with increased DHA dietary supply was also noted, with an apparent increase in catabolism between treatment DHA-5 and DHA-14. No major effects of dietary DHA levels ranging from 0.0 to 30.2 mg.g-1Artemia DW between 22 and 35DAH could be observed on larval performance. However, light intensity probably had an impact on post-larvae performance, mainly at high intensities. Furthermore, the tube feeding trial suggested a possible DHA requirment between 5.1 and 14.6 mg g-1 of Artemia dry weight.

Dissertação mest., Aquacultura e Pescas, Universidade do Algarve, 2009 Os ácidos gordos (AG) essenciais presentes nas dietas são tidos como factores críticos no sucesso do cultivo larvar. Tem sido dado um maior destaque aos ácidos docosahexaenóico (DHA) e eicosapentaenóico (EPA) devido às suas funções na integridade celular membranar e predominância nos tecidos. A importância do ácido araquidónico (ARA) no crescimento, sobrevivência e resistência ao stress é também cada vez mais reconhecida. Realizou-se um estudo para determinar os efeitos que diferentes concentrações de ARA em microdietas causam no crescimento, sobrevivência e perfil de ácidos gordos das larvas de dourada. As larvas foram alimentadas durante 25 dias com microdietas, incluindo um período inicial de coalimentação com rotíferos enriquecidos. Foram testadas, em triplicado, quatro microdietas experimentais que diferiam nos níveis de ARA, variando entre 0,4% e 3,0% da matéria seca (ARA0,4/ ARA0,8/ ARA1,5/ ARA3,0). As microdietas apresentavam níveis de HUFA n-3 de 4,6% e um rácio DHA/EPA de 1,4. Mediu-se o crescimento com base no peso seco e taxa de crescimento relativo, e obteve-se a sobrevivência por contagem directa. O perfil em AG dos lípidos totais das larvas foi determinado por cromatografia em fase gasosa. Após 34 dias, não se registaram diferenças significativas no crescimento e sobrevivência, apesar de existir uma tendência nos tratamentos intermédios para um menor crescimento. A composição lipídica dos tecidos reflectiu o perfil de AG das dietas, particularmente quanto ao ARA. O DHA manteve-se constante, enquanto o EPA diminuiu com o aumento de ARA, mesmo com níveis semelhantes de EPA nas dietas, sugerindo uma competição entre estes AG para a incorporação nos tecidos. Até 1,5% nas dietas, o ARA mostrou ser preferencialmente depositado nos tecidos, sendo metabolizado em concentrações superiores (3,0%). O DHA e alguns AG saturados foram preferencialmente retidos enquanto que o EPA e os ácidos linoleico (LA), α- linolénico (ALA) e oleico (OA) foram metabolizados, provavelmente para fins energéticos. Nas condições testadas, as larvas de dourada mostraram uma boa tolerância à variação de ARA nas dietas, de 0,4% a 3,0%. No entanto, o crescimento não foi afectado nem se verificou uma melhoria da sobrevivência.

Dissertação mest., Aquacultura e Pescas, Universidade do Algarve, 2009 The general aim of this study was to understand the underlying factors responsible for the individual variation in growth of juvenile Senegalese sole (Solea senegalensis). Senegalese sole is a species of high commercial value and high interest for aquaculture in Europe, therefore it would be important to understand these individual variations. Understanding the causes for individual variation in growth in relation with the feed intake, metabolic rate and response to stress contributes to maximize the production efficiency by reducing food waste and improving water quality. In order to identify the possible factors responsible for the individual variation in sole growth, its relationship with metabolic rate, stress response and feed intake was determined. Twelve fish with 18.49 ± 2.94g of initial weight were kept in standard conditions and feed once a day, during a period of six months. Individual oxygen consumption measurements in Sole juveniles were determined by flow-through respirometry at standard conditions, after the fish were fed a single meal and after a stressful condition. Blood samples for plasma cortisol, were taken from all fish at the start of the experiment (control, indicative of basal levels) and after stress exposure. Quantification of individual feed intake was performed by incorporation with radio-opaque ballotinis glass beads in a dry feed, followed by radiography to quantify the amount of ingested pellets. Individual fish exhibited pronounced variation in growth (final weight ranging from 30.45 to 67.53g), oxygen consumption of fasted fish (108.0 to 447.4 μmol/g/h), oxygen consumption of fed fish (174.7 μmol/g/h to 813.5 μmol/g/h), oxygen consumption after emersion stress (186.8 μmol/g/h to 376.7 μmol/g/h), and plasma cortisol after emersion stress (4.81 ng/ml to 46.45 ng/ml). Individual differences in metabolic rate do not contribute to explain individual differences in growth. However, after emersion stress individual differences in stress response seem to play a role in explaining individual differences in growth, what may result from different copying styles. Sole feed intake as measured by X-ray does not seem to be a good indicator of growth rate. The oxygen consumption increases both when fish are fed and after an emersion stress, as result of additive costs of growth and stress to the cost of maintenance. All together, this study suggests that individual variation of growth in Solea senegalensis is essentially due to genetic variation, and its reduction may accomplished when genetic selection programs are adopted. Furthermore, a study with a larger number of fish and over a larger time period would be important to check some of the trends found in this thesis between growth potential, metabolic rate and coping styles of Senegalese sole.