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- Intra-adrenal interactions in fish: Catecholamine stimulated cortisol release in sea bass (Dicentrarchus labrax L.)Publication . Rotllant, J.; Ruane, N. M.; Dinis, Maria Teresa; Canario, Adelino V. M.; Power, DeborahThe effect of the catecholamines, adrenaline and noradrenaline, on sea bass (Dicentrarchus labrax) and sea bream (Sparus auratus) interrenal cortisol production was studied in vitro using a dynamic superfusion system technique. Increasing concentrations of catecholamines (10−6, 10−8 and 10−10 M) stimulated cortisol production in a dose-dependent manner, in sea bass only. The increase in cortisol production stimulated by adrenaline (10−6 M) and noradrenaline (10−6 M) was inhibited by sotalol (2×10−5 M), but not by prazosin suggesting that catecholamines stimulate cortisol release through the β-receptor subtype. To evaluate catecholamine-induced signal transduction in head kidney cells, measurements of cAMP production and [H3]myo-inositol incorporation were determined in head kidney cell suspensions. Adrenaline and noradrenaline (10−6 M) increased cAMP production, but had no effect on total inositol phosphate accumulation. These results indicate that catecholamines released from the chromaffin cells within the interrenal tissue may act as a paracrine factor to stimulate interrenal steroidogenesis in the sea bass.
- High stocking density induces crowding stress and affects amino acid metabolism in Senegalese sole Solea senegalensis (Kaup 1858) juvenilesPublication . Costas, B.; Aragão, C.; Mancera, J. M.; Dinis, Maria Teresa; Conceição, L. E. C.; Refojos, B. C.Fish held at high stocking densities are generally exposed to chronic stress situations that impose severe energy demands and may predispose the ¢sh to infection. Senegalese sole Solea senegalensis (Kaup) juveniles (78.8 18.9 g body weight) were maintained at low (LSD; 4 kg m2 at the end of the experiment), medium (MSD; 9 kg m2 ) and high (HSD;14 kg m2 ) stocking densities during a period of 63 days. Although disease outbreaks were observed in ¢sh reared at HSD, growth and food consumption did not vary among di¡erent treatments. Results from plasma cortisol and free amino acids (FAAs) showed signi¢- cant di¡erences among di¡erent rearing densities pointing to HSD as stressful rearing condition.
- Stress response and changes in amino acid requirements in Senegalese sole (Solea senegalensis Kaup 1858)Publication . Aragão, C.; Corte-Real, Joana; Costas, B.; Dinis, Maria Teresa; Conceição, L. E. C.Fish in aquaculture are often exposed to various stressors that may change their ability to survive or limit growth. Amino acids are used for processes other than growth, including stress response. This study intended to analyse how repeated acute handling stress can affect growth and amino acid requirements in fish. Senegalese sole juveniles were weekly held in the air during 3min (Handling) for 9 weeks; Control groups were left undisturbed. Growth and plasma levels of stress indicators and of free amino acids were assessed at the end of the experiment. Plasma cortisol and osmolality levels showed that fish in the Handling treatment were stressed, but growth was unaffected. Plasma amino acid concentrations indicate that their requirements in stressed fish were altered, which probably reflects the synthesis of proteins or other specific compounds related to stress response.
- Feed deprivation in Senegalese sole (Solea senegalensis Kaup, 1858) juveniles: Effects on blood plasma metabolites and free amino acid levelsPublication . Costas, B.; Aragão, C.; Ruiz-Jarabo, I.; Vargas-Chacoff, L.; Arjona, F. J.; Dinis, Maria Teresa; Mancera, J. M.; Conceição, L. E. C.The effects of prolonged feed deprivation were assessed on blood plasma metabolites and free amino acid levels in Solea senegalensis. Juvenile specimens were maintained at two experimental conditions (24 h fasted and 21 days feed-deprived). In feed-deprived fish, relative growth rate and hepatosomatic index as well as plasma triglycerides and proteins levels were significantly lower.
- Optimizing rearing and welfare in Senegalese sole (Solea senegalesensis) broodstock: effect of ambient light intensity and handling time on stress responsePublication . Figueiredo, Filipe; Aragão, Cláudia; Pinto, Wilson; Dinis, Maria Teresa; Oliveira, CatarinaBroodstock rearing conditions and handling procedures should be optimized in aquaculture species in order to benefit fish welfare and guarantee optimal conditions for spawning. In teleosts, basal cortisol levels display daily rhythms, oscillating along the 24 h of the day. In this sense, handling fish at different moments of the day may lead to different stress responses. The present study aimed at investigating the optimal rearing conditions for Senegalese sole broodstock, considering ambient light intensity and handling time. The optimal light intensity (50, 100 or 200 lx) was investigated by measuring fish cortisol levels and monitoring locomotor activity rhythms under each intensity tested. Results showed a significant increase in cortisol levels of fish exposed to 200 lx, when compared to values obtained under 100 lx, accompanied by changes in locomotor activity rhythms in both tanks under study. These results suggested that 200 lx may be too high as light intensity for this species, whereas 100 lx seems to be more adequate. Also, daily rhythms of stress response were investigated in breeders from different origins (Wild and first generation, G1). Basal cortisol levels and cortisol stress response after an acute stressor (air exposure) were monitored at two distinct moments of the day (Mid-Light and Mid-Dark). Basal levels were higher during the day in the wild group, while G1 fish seemed to have lost the daily fluctuations in basal cortisol plasma levels, as well as their daily rhythms of locomotor activity. Both groups showed lower stress responses during night-time, an indication that this is an adequate period of the day to handle this species. Senegalese sole breeders born in captivity presented more pronounced stress responses when compared to wild fish, reflecting their different life history in terms of stress challenges.