Vander Bruno dos Santos

Curvas de crescimento morfométrico de piracanjuba (Brycon orbignyanus)

Conduziu-se um experimento no setor de piscicultura da Universidade Federal de Lavras M.G., com o objetivo de estabelecer curvas de crescimento morfometrico em funcao do peso corporal para a piracanjuba (Brycon orbignyanus). Alevinos de piracanjuba foram cultivados em viveiros de terra e alimentados com racao comercial ate atingirem peso aproximado de 1 kg. Durante o periodo experimental realizaram-se amostragens aleatorias, onde foram avaliadas as medidas morfometricas comprimento da cabeca (CCAB), comprimento padrao (CP), altura (AND) e largura (LND) tomada no 1oraio da nadadeira dorsal e as razoes morfometricas (CCAB/CP, AND/CP, LND/CP, AND/LND) utilizando-se as funcoes de Brody, von Bertalanffy, Gompertz e Logistica. As funcoes estudadas apresentaram bom ajuste para todas as medidas morfometricas e para a razao CCAB/CP. As funcoes de Brody, von Bertalanffy e Gompertz apresentaram qualidades de ajuste semelhantes e superiores a funcao Logistica para as medidas morfometricas. Para a razao CCAB/CP a funcao Logistica apresentou-se superior as demais. A taxa de crescimento da CCAB e LND foi superior as do CP e AND, indicando um crescimento mais rapido da cabeca e largura do que do comprimento padrao e altura. Conclui-se que todos os modelos estudados apresentaram bom ajuste, sendo o de Brody e o de von Bertalanffy os que descrevem melhor o crescimento morfometrico da piracanjuba.

Rearing temperature induces changes in muscle growth and gene expression in juvenile pacu (Piaractus mesopotamicus)

Pacu (Piaractus mesopotamicus) is a fast-growing fish that is extensively used in Brazilian aquaculture programs and shows a wide range of thermal tolerance. Because temperature is an environmental factor that influences the growth rate of fish and is directly related to muscle plasticity and growth, we hypothesized that different rearing temperatures in juvenile pacu, which exhibits intense muscle growth by hyperplasia, can potentially alter the muscle growth patterns of this species. The aim of this study was to analyze the muscle growth characteristics together with the expression of the myogenic regulatory factors MyoD and myogenin and the growth factor myostatin in juvenile pacu that were submitted to different rearing temperatures. Juvenile fish (1.5 g weight) were distributed in tanks containing water and maintained at 24°C (G24), 28 °C (G28) and 32 °C (G32) (three replicates for each group) for 60 days. At days 30 and 60, the fish were anesthetized and euthanized, and muscle samples (n=12) were collected for morphological, morphometric and gene expression analyses. At day 30, the body weight and standard length were lower for G24 than for G28 and G32. Muscle fiber frequency in the <25 μm class was significantly higher in G24, and the >50 μm class was lower in G24. MyoD gene expression was higher in G24 compared with that in G28 and G32, and myogenin and myostatin mRNA levels were higher in G24 than G28. At day 60, the body weight and the standard length were higher in G32 but lower in G24. The frequency distribution of the <25 μm diameter muscle fibers was higher in G24, and that of the >50 μm class was lower in G24. MyoD mRNA levels were higher in G24 and G32, and myogenin mRNA levels were similar between G24 and G28 and between G24 and G32 but were higher in G28 compared to G32. The myostatin mRNA levels were similar between the studied temperatures. In light of our results, we conclude that low rearing temperature altered the expression of muscle growth-related genes and induced a delay in muscle growth in juvenile pacu (P. mesopotamicus). Our study provides a clear example of thermally induced phenotypic plasticity in pacu fish and shows that changing the rearing temperature during the juvenile stage can have a considerable effect on gene expression and muscle growth in this species.

Food restriction increase the expression of mTORC1 complex genes in the skeletal muscle of juvenile pacu (Piaractus mesopotamicus)

Skeletal muscle is capable of phenotypic adaptation to environmental factors, such as nutrient availability, by altering the balance between muscle catabolism and anabolism that in turn coordinates muscle growth. Small noncoding RNAs, known as microRNAs (miRNAs), repress the expression of target mRNAs, and many studies have demonstrated that miRNAs regulate the mRNAs of catabolic and anabolic genes. We evaluated muscle morphology, gene expression of components involved in catabolism, anabolism and energetic metabolism and miRNAs expression in both the fast and slow muscle of juvenile pacu (Piaractus mesopotamicus) during food restriction and refeeding. Our analysis revealed that short periods of food restriction followed by refeeding predominantly affected fast muscle, with changes in muscle fiber diameter and miRNAs expression. There was an increase in the mRNA levels of catabolic pathways components (FBXO25, ATG12, BCL2) and energetic metabolism-related genes (PGC1α and SDHA), together with a decrease in PPARβ/δ mRNA levels. Interestingly, an increase in mRNA levels of anabolic genes (PI3K and mTORC1 complex: mTOR, mLST8 and RAPTOR) was also observed during food restriction. After refeeding, muscle morphology showed similar patterns of the control group; the majority of genes were slightly up- or down-regulated in fast and slow muscle, respectively; the levels of all miRNAs increased in fast muscle and some of them decreased in slow muscle. Our findings demonstrated that a short period of food restriction in juvenile pacu had a considerable impact on fast muscle, increasing the expression of anabolic (PI3K and mTORC1 complex: mTOR, mLST8 and RAPTOR) and energetic metabolism genes. The miRNAs (miR-1, miR-206, miR-199 and miR-23a) were more expressed during refeeding and while their target genes (IGF-1, mTOR, PGC1α and MAFbx), presented a decreased expression. The alterations in mTORC1 complex observed during fasting may have influenced the rates of protein synthesis by using amino acids from protein degradation as an alternative mechanism to preserve muscle phenotype and metabolic demand maintenance.

Differential microRNA Expression in Fast- and Slow-Twitch Skeletal Muscle of Piaractus mesopotamicus during Growth.

Pacu (Piaractus mesopotamicus) is a Brazilian fish with a high economic value in pisciculture due to its rusticity and fast growth. Postnatal growth of skeletal muscle in fish occurs by hyperplasia and/or hypertrophy, processes that are dependent on the proliferation and differentiation of myoblasts. A class of small noncoding RNAs, known as microRNAs (miRNAs), represses the expression of target mRNAs, and many studies have demonstrated that miR-1, miR-133, miR-206 and miR-499 regulate different processes in skeletal muscle through the mRNA silencing of hdac4 (histone deacetylase 4), srf (serum response factor), pax7 (paired box 7) and sox6 ((sex determining region Y)-box 6), respectively. The aim of our work was to evaluate the expression of these miRNAs and their putative target mRNAs in fast- and slow-twitch skeletal muscle of pacu during growth. We used pacus in three different development stages: larval (aged 30 days), juvenile (aged 90 days and 150 days) and adult (aged 2 years). To complement our study, we also performed a pacu myoblast cell culture, which allowed us to investigate miRNA expression in the progression from myoblast proliferation to differentiation. Our results revealed an inverse correlation between the expression of the miRNAs and their target mRNAs, and there was evidence that miR-1 and miR-206 may regulate the differentiation of myoblasts, whereas miR-133 may regulate the proliferation of these cells. miR-499 was highly expressed in slow-twitch muscle, which suggests its involvement in the specification of the slow phenotype in muscle fibers. The expression of these miRNAs exhibited variations between different development stages and between distinct muscle twitch phenotypes. This work provides the first identification of miRNA expression profiles in pacu skeletal muscle and suggests an important role of these molecules in muscle growth and in the maintenance of the muscle phenotype.

Influence of temperature and exercise on growth performance, muscle, and adipose tissue in pacus (Piaractus mesopotamicus)

The aim of this study was to evaluate the effects of temperature and swimming exercise on fish growth in pacus (Piaractus mesopotamicus). Pacus weighing 0.9 - 1.9g and 2.7 - 4.2cm in standard length were cultivated at an initial density of 120 fish m-3 in 3 recirculation systems containing 6 water tanks at a volume of 0.5m3 each at temperatures of 24, 28 and 32°C. At each temperature, three tanks were modified to generate exercise activity in the specimens and force the fish to swim under a current speed of 27.5cms-1. At the end of the experiment, the following metrics were evaluated: fish performance, morphometry (length, width, height and perimeter in different body positions), and the diameter and density of muscle and subcutaneous ventral adipose tissues. At 28°C, pacus were both heavier and had greater weight gain after 240 days of cultivation. Additionally, exercise improved the feed conversion. An increase of 4°C (30°C) did not provide any improvement in the performance of the fish. However, swimming exercise improved the performance of pacus, providing increases of 38% and a 15% improvement in feed conversion. Both temperature and exercise influenced the body morphology (especially in the caudal region) and the cellularity of white and red muscle fibers and adipocytes.

Influence of rearing temperature on muscle growth and adipose tissue in Nile tilapia (Oreochromis niloticus) strains

This study aimed to evaluate the effect of temperature on the tissue growth of Red, GIFT and Supreme tilapia strains. Fingerlings of approximately 1.4 g from male populations were reared for a period of 60 days, in three recirculating systems, each system containing 6 water tanks of 0.5 m3, at three temperatures (22, 28 and 30oC). Ten fish of each recirculation system and each temperature studied were sampled. Fishes have been anesthetized, euthanized and weighed. The samplings have been done from the dorsal musculature, caudal, visceral and ventral subcutaneous adipose tissue. Histological sections were prepared and evaluated to determine the diameter of the cells. The experimental design was completely randomized factorial 3 X 3 (strain X temperature). Analysis of variance was performed and means were compared. Higher weights were found for fish reared at 30°C (56.23 g) compared to those grown at 28 (42.12 g) or 22°C (10.52 g). The cooled water temperature (22°C) may have contributed to the hypertrophy of white muscle fibers and visceral adipocytes from tilapia, compared to 28 or 30oC. Red Tilapia, GIFT and Supreme strains show differences in muscle growth and adipose tissues in response to temperature of cultivation.