Loading...
17 results
Search Results
Now showing 1 - 10 of 17
- Nutrition, quality and performance in marine fish larvaePublication . Conceição, L. E. C.; Alves-Martins, D.; Engrola, S.; Gavaia, Paulo J.; Richard, Nadège; Aragão, C.O cultivo de larvas de peixes marinhos é caracterizado por altas mortalidades e por problemas de qualidade, nomeadamente malformações esqueléticas. A solução de parte destes problemas passa por uma melhor compreensão dos requisitos nutricionais. Este trabalho pretende fazer uma revisão de trabalhos recentes que demonstram como os aminoácidos, os ácidos gordos e a vitamina K, mas também o regime alimentar, podem influenciar a qualidade e a performance das larvas de peixes marinhos.
- What determines growth potential and juvenile quality of farmed fish species?Publication . Valente, L. M. P.; Moutou, K. A.; Conceição, L. E. C.; Engrola, S.; Fernandes, J. M. O.; Johnston, Ian A.Enhanced production of high quality and healthy fry is a key target for a successful and competitive expansion of the aquaculture industry. Although large quantities of fish larvae are produced, survival rates are often low or highly variable and growth potential is in most cases not fully exploited, indicating significant gaps in our knowledge concerning optimal nutritional and culture conditions. Understanding the mechanisms that control early development and muscle growth are critical for the identification of time windows in development that introduce growth variation, and improve the viability and quality of juveniles. This literature review of the current state of knowledge aims to provide a framework for a better understanding of fish skeletal muscle ontogeny, and its impact on larval and juvenile quality as broadly defined. It focuses on fundamental biological knowledge relevant to larval phenotype and quality and, in particular, on the factors affecting the development of skeletal muscle. It also discusses the available methodologies to assess growth and larvae/juvenile quality, identifies gaps in knowledge and suggests future research directions. The focus is primarily on the major farmed non-salmonid fish species in Europe that include gilthead sea bream, European sea bass, turbot, Atlantic cod, Senegalese sole and Atlantic halibut.
- Novel methodologies in marine fish larval nutritionPublication . Conceição, L. E. C.; Aragão, C.; Richard, Nadège; Engrola, S.; Gavaia, Paulo J.; Mira, Sara; Dias, J.Major gaps in knowledge on fish larval nutritional requirements still remain. Small larval size, and difficulties in acceptance of inert microdiets, makes progress slow and cumbersome. This lack of knowledge in fish larval nutritional requirements is one of the causes of high mortalities and quality problems commonly observed in marine larviculture. In recent years, several novel methodologies have contributed to significant progress in fish larval nutrition. Others are emerging and are likely to bring further insight into larval nutritional physiology and requirements. This paper reviews a range of new tools and some examples of their present use, as well as potential future applications in the study of fish larvae nutrition. Tube-feeding and incorporation into Artemia of 14C-amino acids and lipids allowed studying Artemia intake, digestion and absorption and utilisation of these nutrients. Diet selection by fish larvae has been studied with diets containing different natural stable isotope signatures or diets where different rare metal oxides were added. Mechanistic modelling has been used as a tool to integrate existing knowledge and reveal gaps, and also to better understand results obtained in tracer studies. Population genomics may assist in assessing genotype effects on nutritional requirements, by using progeny testing in fish reared in the same tanks, and also in identifying QTLs for larval stages. Functional genomics and proteomics enable the study of gene and protein expression under various dietary conditions, and thereby identify the metabolic pathways which are affected by a given nutrient. Promising results were obtained using the metabolic programming concept in early life to facilitate utilisation of certain nutrients at later stages. All together, these methodologies have made decisive contributions, and are expected to do even more in the near future, to build a knowledge basis for development of optimised diets and feeding regimes for different species of larval fish.
- Individual differences in cortisol levels and behaviour of Senegalese sole (Solea senegalensis) juveniles: evidence for coping stylesPublication . Silva, P. I. M.; Martins, C. I. M.; Engrola, S.; Marino, G.; Øverli, Ø.; Conceição, L. E. C.Individual variation in stress physiology and behaviour has been previously reported in several fish species. As seen in other vertebrates, existence of stress coping styles seemsto be reflected by the presence of individual variation. Aggressive behaviour, amongst others, is one of the most commonly used parameters to characterize coping styles. However, not all fish species exhibit aggressive behaviour, such as the flatfish Senegalese sole, Solea senegalensis (Kaup, 1858). Therefore, the goal of this study was to determine the magnitude of individual variation in behavioural parameters other than aggression (feeding motivation and activity during stress) as well as in growth and stress response in Senegalese sole. The relationship between these variables was investigated to determine whether they could be used as indicators of coping styles. Thirty-six juvenile fish (9.9 2.2 g) were individually housed for 73 days. Feedingmotivation,measured as the time(in s) taken by each fish to react to feed,was determined on days 10, 17, 24 and 31. Bloodsamples for plasmacortisol were collected on days 51 and 71 for determination of undisturbed and stress levels, respectively. Thestress test consisted of holding each fish individually in a net, outside the water, for 3min. Duration of escape attempts, i.e. the time takenby each fish to stop struggling (in an attempt to escape) in the net, was quantified. The results showed a pronounced individual variation in both control (CV = 54%) and acute stress (CV = 71%) cortisol levels. Senegalese sole also exhibited high coefficient of variationinthebehavioural parameters:75%in feeding latency and96%induration of escape attempts. Growth (RGR = 1.17 0.38) showed to be the parameter with lower variation of only 32% and was not correlated with any of the measured parameters. A significant correlation between undisturbed cortisol levels and duration of escape attempts was found. Undisturbed cortisol levels (8.08 4.36 ng/ml) were negatively correlated with duration of escape attempts (P = 0.009, rs = 0.503). Correlations between plasma cortisol levels after stress (398.45 282.67 ng/ml) and the behavioural parameters were not found. The observed individual variation in behaviour and stress physiology as well as their relationship suggests the existence of coping styles in Senegalese sole where proactive individuals exhibit shorter feeding latency, higher duration of escape attempts and lower undisturbed cortisol levels than passive individuals.
- Incubation temperature induces changes in muscle cellularity and gene expression in Senegalese sole (Solea senegalensis)Publication . Campos, C.; Valente, L. M. P.; Conceição, L. E. C.; Engrola, S.; Sousa, V.; Rocha, E.; Fernandes, J. M. O.Fertilised eggs of Senegalese sole were incubated at 15, 18 or 21 °C, and after hatching all larvae were reared at 21 °C until 30 days post-hatch. By this point larvae from the 18 or 21 °C temperature groups had 11 and 9% more muscle fibres than those from 15 °C, respectively. Hyperplastic growth during metamorphosis was higher in larvae from 18 °C. Embryonic temperature induced gene expression changes, albeit with a variable pattern throughout development. Myf5, myod2, myHC and fst mRNA levels were significantly higher at several stages prior to hatching in embryos incubated at 21 °C, whereas hsp90AB and hsp70 transcripts were present at higher levels in the 15 °C group. Myf5, myod1, myod2, pax7, myog, fst, igf-II, igf1r, hsp90AA and hsp90AB were expressed at higher levels during early development, particularly during somitogenesis. In contrast, mrf4, myHC, mylc2, igf-I, mstn1 and hsp70 were up-regulated at later stages of larval development, namely during and after metamorphosis. This study is the first example of thermal plasticity of myogenesis with prolonged effect in a flatfish.
- Daily oxygen consumption rhythms of Senegalese sole solea senegalensis (Kaup, 1858) juvenilesPublication . Castanheira, Maria Filipa; Martins, C. I. M.; Engrola, S.; Conceição, L. E. C.Senegalese sole is known to be a species with pronounced nocturnal feeding behaviour. However, as for most fish species, there is a lack of knowledge concerning the influence of such biological rhythmon metabolic rate. The aim of this study was to determine whether individual variation in routine and fed metabolic rate was affected by daily light–dark rhythms in juveniles of Senegalese sole. The individual oxygen consumption measurements in Senegalese sole juveniles were determined by flow-through respirometry, at fasted conditions and after the fish were fed a single meal, the meal time started at 0930 h and fish fed ad libitum for 30 min. The measurements were made during 22 h, of which 8 h was in the light and 14 h in the dark, and started immediately after transfer to the respiratory chambers at 1100 h. The results suggest an influence of light–dark cycles in routine metabolism. It was observed that oxygen consumption increased during the dark phase in fasted fish (FAST) but was higher during the light phase in fed fish (FEED). However, when feed is provided during the light phase, juveniles are capable of shifting oxygen consumption rhythms to respond to the energetic demands of digestion and growth. These results suggest that routine metabolism varies according to the species natural habits as Senegalese sole is known to be nocturnal. The findings of this study underline the importance of understanding the biological rhythms of the species under study before metabolic data are interpreted.
- Effect of varying dietary levels of LC-PUFA and vegetable oil sources on performance and fatty acids of Senegalese sole post larvae: Puzzling results suggest complete biosynthesis pathway from C18 PUFA to DHAPublication . Navarro-Guillén, Carmen; Engrola, S.; Castanheira, Maria Filipa; Bandarra, N.; Hachero-Cruzado, Ismael; Tocher, Douglas R.; Conceição, L. E. C.; Morais, S.Lipid nutrition of marine fish larvae has focused on supplying essential fatty acids (EFA) at high levels to meet requirements for survival, growth and development. However, some deleterious effects have been reported suggesting that excessive supply of EFA might result in insufficient supply of energy substrates, particularly in species with lower EFA requirements such as Senegalese sole (Solea senegalensis). This study addressed how the balance between EFA and non-EFA (better energy sources) affects larval performance, body composition and metabolism and retention of DHA, by formulating enrichment emulsions containing two different vegetable oil sources (olive oil or soybean oil) and three DHA levels. DHA positively affected growth and survival, independent of oil source, confirming that for sole post-larvae it is advantageous to base enrichments on vegetable oils supplying higher levels of energy, and supplement these with a DHA-rich oil. In addition, body DHA levels were generally comparable considering the large differences in their dietary supply, suggesting that the previously reported ∆4 fatty acyl desaturase (fad) operates in vivo and that DHA was synthesized at physiologically significant rates through a mechanism involving transcriptional up-regulation of ∆4fad, which was significantly up-regulated in the low DHA treatments. Furthermore, data suggested that DHA biosynthesis may be regulated by an interaction between dietary n − 3 and n − 6 PUFA, as well as by levels of LC-PUFA, and this may, under certain nutritional conditions, lead to DHA production from C18 precursors. The molecular basis of putative fatty acyl ∆5 and ∆6 desaturation activities remains to be fully determined as thorough searches have found only a single (∆4) Fads2-type transcript. Therefore, further studies are required but this might represent a unique activity described within vertebrate fads.
- Temperature affects methylation of the myogenin putative promoter, its expression and muscle cellularity in Senegalese sole larvaePublication . Campos, C.; Valente, L. M. P.; Conceição, L. E. C.; Engrola, S.; Fernandes, J. M. O.Myogenin (myog) encodes a highly conserved myogenic regulatory factor that is involved in terminal muscle differentiation. It has been shown in mammals that methylation of cytosines within the myog promoter plays a major role in regulating its transcription. In the present study, the Senegalese sole (Solea senegalensis) myog putative proximal promoter was identified and found to be highly conserved among teleosts. Therefore, it is plausible that it plays a similar role in controlling myog expression. Cytosine methylation of the myog promoter in skeletal muscle of Senegalese sole larvae undergoing metamorphosis was influenced by rearing temperature. A lower temperature (15°C) significantly increased myog promoter methylation in skeletal muscle, particularly at specific CpG sites, relatively to higher rearing temperatures (18 and 21°C). Myog transcription was downregulated at 15°C, whereas expression of dnmt1 and dnmt3b was upregulated, consistently with the higher myog methylation observed at this temperature. Rearing temperature also affected growth and fast muscle cellularity, producing larger fibers at 21°C. Taken together, our data provide the first evidence of an epigenetic mechanism that may be underlying the temperature-induced phenotypic plasticity of muscle growth in teleosts.
- Evaluation of the skeletal quality in Senegalese sole (Solea Senegalensis, Kaup) reared under intensive vs extensive conditionsPublication . Gavaia, Paulo J.; Richard, Nadège; Dâmaso, L.; Dinis, Maria Teresa; Pousão-Ferreira, P.; Engrola, S.; Conceição, L. E. C.; Cancela, Leonor- Senegalese sole is distributed along the Mediterranean and southwestern Europe, reaching a market price of 20-25 €/kg - Promising species for aquaculture diversification - Control and intensification of culture is reasonably achieved - The high incidence of skeletal anomalies in intensively reared fish represents a constraint to commercial production - Samples from Portugal and Greece were analyzed towards identifying skeletal differences due to rearing conditions
- Thermal conditions during larval pelagic phase influence subsequent somatic growth of Senegalese sole by modulating gene expression and muscle growth dynamicsPublication . Campos, C.; Fernandes, J. M. O.; Conceição, L. E. C.; Engrola, S.; Sousa, V.; Valente, L. M. P.In the present study, Senegalese sole eggs incubated at 20 °C were reared at three different temperatures (15 °C, 18 °C or 21 °C) during the pelagic phase, and then transferred to a common temperature (20 °C) from benthic stage until 100 days post-hatch (dph). Somatic growth, fast muscle cellularity and expression of 15 growth-related genes were compared at the same developmental stage for each temperature (pre-metamorphic larvae, metamorphic larvae, post-metamorphic larvae) and at 83 dph and 100 dph early juveniles. During pre-metamorphosis and metamorphosis, larvae from 21 °C weighed significantly more than those reared at 18 °C or 15 °C (P < 0.001). Relative growth rate (RGR) of pelagic larvae and survival of newly-settled larvae were also higher at 21 °C (P < 0.05). Furthermore, an increase in muscle growth towards the highest temperatures was observed concomitantly with an increase in gene expression, namely myogenic regulatory factors (MRFs), myosins, igf-I and fgf6. After transfer to a common temperature (20 °C), the 15 °C group initiated a process of compensatory growth, inverting relative growth rate values that became the highest, particularly between 83 dph and 100 dph (P < 0.05). This increased growth effort in the 15 °C group was accompanied by an up-regulation of gene expression in fast muscle, particularly in the 83 dph juveniles. Mrf4 and myHC were up-regulated at 15 °C and positive correlations with growth were also found for myog or pax7 (P < 0.05). In contrast, mstn1 was down-regulated at 15 °C (P < 0.05), suggesting a boost in muscle growth. By 100 dph, the 15 °C group had already reached the same weight as the 18 °C and the same length as the 21 °C ones. At this age, the 18 °C juveniles had the largest mean muscle fibre diameter (P < 0.001), and thus fibre hypertrophy seems to be a major growth mechanism relatively to the other groups. Our work shows that temperature during pelagic phase greatly influences the growth trajectory of Senegalese sole juveniles.