Browsing by Author "Pinto, W."
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- Can dietary aromatic amino acid supplementation be beneficial during fish metamorphosis?Publication . Pinto, W.; Rodrigues, V.; Dinis, Maria Teresa; Aragão, C.Aromatic amino acids (AA, phenylalanine and tyrosine) are the precursors of thyroid hormones, which regulate metamorphosis in all vertebrates. In fish, this is a critical developmental stage where physiological requirements for aromatic AA may increase. Therefore, it is possible that dietary aromatic AA supplementation may be beneficial to accomplish a successful transition from larvae to the juvenile stage. This work aimed to assess the effect of dietary aromatic AA supplementation on tyrosine metabolism in species with an accentuated (Senegalese sole, Solea senegalensis) and a less marked (gilthead seabream, Sparus aurata) metamorphosis. For this purpose, either species were fed Artemia and subsequently received or not an aromatic AA supplement through tube-feeding, together with a L-[U-14C] tyrosine marker, throughout metamorphosis. Tyrosine was elected as a tracer since the metabolic fate of this aromatic AA is directly linked to the production of thyroid hormones and metamorphosis. Results showed that dietary phenylalanine supplementation did not increase tyrosine retention in Senegalese sole larvae during metamorphosis, suggesting that this species may not be able to biosynthesise tyrosine from phenylalanine at a sufficient rate to supply its physiological requirements until after metamorphosis. Furthermore, dietary tyrosine supplementation effectively increased tyrosine availability in Senegalese sole body fluids at metamorphosis, most likely for coping with metamorphosis-related processes, such as production of thyroid hormones. Therefore, dietary tyrosine supplementation may be beneficial for Senegalese sole during metamorphosis. On the other hand, results indicated that gilthead seabream larvae do not seem to require an additional supply of aromatic AA during metamorphosis, probably because the physiological requirements for tyrosine do not increase during this developmental stage. The different results observed for Senegalese sole and gilthead seabream are probably related to the complexity of metamorphosis that each species undergoes and to the needs for production of thyroid hormones, which seems to affect aromatic AA requirements during this critical stage of development. These findings may be important for physiologists, fish nutritionists and for the flatfish aquaculture industry.
- Cloning, tissue and ontogenetic expression of the taurine transporter in the flatfish Senegalese sole (Solea senegalensis)Publication . Pinto, W.; Rønnestad, I.; Jordal, A. E. O.; Dinis, Maria Teresa; Aragão, C.Flatfish species seem to require dietary taurine for normal growth and development. Although dietary taurine supplementation has been recommended for flatfish, little is known about the mechanisms of taurine absorption in the digestive tract of flatfish throughout ontogeny. This study described the cloning and ontogenetic expression of the taurine transporter (TauT) in the flatfish Senegalese sole (Solea senegalensis). Results showed a high similarity between TauT in Senegalese sole and other vertebrates, but a change in TauT amino acid sequences indicates that taurine transport may differ between mammals and fish, reptiles or birds. Moreover, results showed that Senegalese sole metamorphosis is an important developmental trigger to promote taurine transport in larvae, especially in muscle tissues, which may be important for larval growth. Results also indicated that the capacity to uptake dietary taurine in the digestive tract is already established in larvae at the onset of metamorphosis. In Senegalese sole juveniles, TauT expression was highest in brain, heart and eye. These are organs where taurine is usually found in high concentrations and is believed to play important biological roles. In the digestive tract of juveniles, TauT was more expressed in stomach and hindgut, indicating that dietary taurine is quickly absorbed when digestion begins and taurine endogenously used for bile salt conjugation may be recycled at the posterior end of the digestive tract. Therefore, these results suggest an enterohepatic recycling pathway for taurine in Senegalese sole, a process that may be important for maintenance of the taurine body levels in flatfish species.
- Dietary taurine supplementation enhances metamorphosis and growth potential of Solea senegalensis larvaePublication . Pinto, W.; Figueira, L.; Ribeiro, L.; Yúfera, M.; Dinis, Maria Teresa; Aragão, C.The effect of dietary taurine supplementation on growth performance, metamorphosis success and amino acid metabolism of Senegalese sole (Solea senegalensis) larvae was investigated. These parameters were assessed in larvae fed control and taurine supplemented microcapsules during the pelagic phase. Subsequently, a similar evaluation was carried out in newly settled larvae fed upon Artemia, in order to verify the effect of earlier dietary taurine supplementation in larvae reared under improved feeding conditions. Results showed that dietary taurine supplementation did not affect larval growth performance and metamorphosis during the pelagic phase. However, by the end of the trial, Senegalese sole previously fed taurine supplemented microcapsules had a significantly higher growth performance and metamorphosis completion success than larvae fed control microcapsules. These differences were likely related to the improvement of feeding conditions upon settlement, which probably helped revealing the positive effects of earlier dietary taurine supplementation on Senegalese sole performance. Additionally, Senegalese sole may have benefited from taurine antioxidant properties during metamorphosis, since larval antioxidant defences may saturate at this stage. Furthermore, results from metabolic trials have shown that dietary taurine supplementation significantly increased amino acid retention in Senegalese sole larvae when a concomitant increase of taurine body levels was found. Therefore, an increase in larval growth potential and metamorphosis success was observed under dietary taurine supplementation and these results may help understanding why dietary taurine supplementation has been reported to simultaneously increase taurine body levels and growth performance in other fish species, leading to a better comprehension on the role of taurine during fish development.
- Fast growing greater amberjack post-larvae require a high energy-high protein weaning dietPublication . Navarro-Guillén, Carmen; Conceicao, L. E. C.; Pinto, W.; Siguero, I; Urrutia, P.; Moyano, F. J.; Yufera, M.Larvae and early juveniles of fast-growing fish species show tremendous growth potential, leading to higher requirements for protein, high-unsaturated fatty acids, and other nutrients. Several commercial weaning diets with relatively high success have been developed for low/moderate-growing species however, additional challenges are outlined to meet growth potential and energy requirements of such fast-growing species. The objective of the present study was to evaluate two commercial microdiets for marine fish, one having simultaneously a very high protein and high lipid contents (HIGH), and another (MOD) with a high protein and moderate lipid content, in a growth performance trial with greater amberjack post-larvae from 33 to 78 days after hatching. Moreover, histological preparations of liver, anterior and posterior intestine were assessed for hepatic and intestinal lipid inclusions quantification and gut epithelial brush height measurement. Activities of the digestive enzymes: pepsin, trypsin, chymotrypsin, lipase and amylase were also analyzed. Post-larvae fed HIGH microdiet exhibited higher final weight and lower feed conversion ratio that those fed on MOD microdiet. Liver displayed a higher level of lipid inclusions for the MOD diet than for HIGH diet. Moreover, enterocytes of posterior intestine presented a much higher level of supranuclear vacuoles for the HIGH diet compared to MOD diet. The lower Trypsin/Chymotrypsin ratio observed at the end of the experiment in larvae fed on MOD diet may indicate a deficiency in protein of this diet. Together, these results support that larvae of greater amberjack, and likely other fast-growing marine fish species, require high protein-high lipid microdiets. The use of microdiets developed targeting slower growing marine species may lead to sub-optimal performances in fast-growing larvae.
- Growth, stress response and free amino acid levels in Senegalese sole (Solea senegalensis Kaup 1858) chronically exposed to exogenous ammoniaPublication . Pinto, W.; Aragão, C.; Soares, Florbela; Dinis, Maria Teresa; Conceição, L. E. C.Stressful husbandry conditions are likely to a¡ect growth and amino acid metabolism in ¢sh. In this study, chronic ammonia exposure was used to test the e¡ects of a stressor on growth and amino acid metabolism of Senegalese sole juveniles. The ¢sh were exposed for 52 days to 11.6 mg L 1 [low-TAN (L-TAN)] or 23.2 mg L 1 [high-TAN (H-TAN)] of total ammonia nitrogen (TAN), or to 0 mg L 1 (Control). Growth in L-TAN groups was slightly but signi¢- cantly di¡erent from the Control groups [relative growth rate (RGR50.35 0.13 and 0.52 0.23% day 1respectively)]. In H-TAN groups, growth was severely a¡ected (RGR50.01 0.13% day 1 ).
- How does fish metamorphosis affect aromatic amino acid metabolism?Publication . Pinto, W.; Figueira, L.; Dinis, Maria Teresa; Aragão, C.Aromatic amino acids (AAs, phenylalanine and tyrosine) may be specifically required during fish metamorphosis, since they are the precursors of thyroid hormones which regulate this process. This project attempted to evaluate aromatic AA metabolism during the ontogenesis of fish species with a marked (Senegalese sole; Solea senegalensis) and a less accentuated metamorphosis (gilthead seabream; Sparus aurata). Fish were tube-fed with three l-[U-14C] AA solutions at pre-metamorphic, metamorphic and post-metamorphic stages of development: controlled AA mixture (Mix), phenylalanine (Phe) and tyrosine (Tyr). Results showed a preferential aromatic AA retention during the metamorphosis of Senegalese sole, rather than in gilthead seabream. Senegalese sole’s highly accentuated metamorphosis seems to increase aromatic AA physiological requirements, possibly for thyroid hormone production. Thus, Senegalese sole seems to be especially susceptible to dietary aromatic AA deficiencies during the metamorphosis period, and these findings may be important for physiologists, fish nutritionists and the flatfish aquaculture industry.
- Is dietary taurine supplementation beneficial for gilthead seabream (Sparus aurata) larvae?Publication . Pinto, W.; Figueira, L.; Santos, A.; Barr, Y.; Helland, S.; Dinis, Maria Teresa; Aragão, C.This study evaluated the effect of dietary taurine supplementation on the growth performance and methionine metabolism of gilthead seabream larvae. For this purpose, a growth experiment was carried out in which seabream larvae were fed upon rotifers supplemented with “blank” or taurine-enriched liposomes. A complementary trial was also done in which seabream larvae fed with live prey were subsequently tube-fed a solution containing a L-[U-14C] methionine with or without a taurine supplement. Results from the growth experiment showed that rotifers were successfully enriched with taurine, but no effects were observed on larval growth performance, survival or amino acid composition. Furthermore, dietary taurine supplementation did not result in an increase of larval taurine levels, a factor that may have been determinant for the absence of effects observed on growth performance. In the tube-feeding trial, results showed that dietary taurine supplementation led to an increase of methionine retention in larvae. These findings suggest the existence of an active taurine biosynthesis pathway for gilthead seabream during the larval stage. Hence, gilthead seabream may not be dependent on dietary taurine to maintain the taurine body pool, since it may convert taurine from methionine if required. Taken together, the results from this study indicate that dietary taurine supplementation does not seem to enhance the larval growth performance in fish species able to biosynthesise taurine during this stage, which seems to be the case of gilthead seabream. However, this study also showed that in these species, dietary taurine supplementation may ultimately affect larval metabolism by increasing methionine availability for several important physiological purposes, contributing to a better understanding on the role of taurine during the early life stages of fish development.