Review: Understanding fish muscle biology in the indeterminate growth species pacu (Piaractus mesopotamicus).

The muscle phenotype of fish is regulated by numerous factors that, although widely explored, still need to be fully understood. In this context, several studies aimed to unravel how internal and external stimuli affect the muscle growth of these vertebrates. The pacu (Piaractus mesopotamicus) is a species of indeterminate muscular growth that quickly reaches high body weight. For this reason, it adds great importance to the productive sector, along with other round fish. In this context, we aimed to compile studies on fish biology and skeletal muscle growth, focusing on studies by our research group that used pacu as an experimental model along with other species. Based on these studies, new muscle phenotype regulators were identified and explored in vivo, in vitro, and in silico studies, which strongly contribute to advances in understanding muscle growth mechanisms with future applications in the productive sector.

Identification of Novel Genes Associated with Fish Skeletal Muscle Adaptation during Fasting and Refeeding Based on a Meta-Analysis.

The regulation of the fish phenotype and muscle growth is influenced by fasting and refeeding periods, which occur in nature and are commonly applied in fish farming. However, the regulators associated with the muscle responses to these manipulations of food availability have not been fully characterized. We aimed to identify novel genes associated with fish skeletal muscle adaptation during fasting and refeeding based on a meta-analysis. Genes related to translational and proliferative machinery were investigated in pacus (Piaractus mesopotamicus) subjected to fasting (four and fifteen days) and refeeding (six hours, three and fifteen days). Our results showed that different fasting and refeeding periods modulate the expression of the genes mtor, rps27a, eef1a2, and cdkn1a. These alterations can indicate the possible protection of the muscle phenotype, in addition to adaptive responses that prioritize energy and substrate savings over cell division, a process regulated by ccnd1. Our study reveals the potential of meta-analysis for the identification of muscle growth regulators and provides new information on muscle responses to fasting and refeeding in fish that are of economic importance to aquaculture.

Amino acid profile of food fishes with potential to diversify fish farming activity.

In Brazil, 47% of the fish farming correspond to the tilapia species, and the main producers are the south and northeast regions. This work aimed at characterizing the amino acid profile of three fishes with the potential for rearing and diversification in Brazil and worldwide. The fishes grass carp (Ctenopharyngodon idella), pacu (Piaractus mesopotamicus), and catfish (Ictalurus punctatus) were obtained from a rural property located in the city of Pato Branco, PR, Brazil, and analyzed regarding the amino acid composition through High-Performance Liquid Chromatography. The amino acid profile showed the presence of glutamic acid, followed by lysine, aspartic acid, and leucine as the most prominent amino acids for the three fishes. Among the studied species, the grass carp presented the highest content of essential amino acids, registering all values superior to the minimum recommendation standards determined by the Food and Agriculture Organization of the United Nations (FAO). The disclosure of the significant nutritional value presented by these species consolidate their protein quality and expand possibilities to improve the fish farming and development of derivative products.

Using aerobic exercise to evaluate sub-lethal tolerance of acute warming in fishes.

We investigated whether fatigue from sustained aerobic swimming provides a sub-lethal endpoint to define tolerance of acute warming in fishes, as an alternative to loss of equilibrium (LOE) during a critical thermal maximum (CTmax) protocol. Two species were studied, Nile tilapia (Oreochromis niloticus) and pacu (Piaractus mesopotamicus). Each fish underwent an incremental swim test to determine gait transition speed (UGT), where it first engaged the unsteady anaerobic swimming mode that preceded fatigue. After suitable recovery, each fish was exercised at 85% of their own UGT and warmed 1°C every 30 min, to identify the temperature at which they fatigued, denoted as CTswim Fish were also submitted to a standard CTmax, warming at the same rate as CTswim, under static conditions until LOE. All individuals fatigued in CTswim, at a mean temperature approximately 2°C lower than their CTmax Therefore, if exposed to acute warming in the wild, the ability to perform aerobic metabolic work would be constrained at temperatures significantly below those that directly threatened survival. The collapse in performance at CTswim was preceded by a gait transition qualitatively indistinguishable from that during the incremental swim test. This suggests that fatigue in CTswim was linked to an inability to meet the tissue oxygen demands of exercise plus warming. This is consistent with the oxygen and capacity limited thermal tolerance (OCLTT) hypothesis, regarding the mechanism underlying tolerance of warming in fishes. Overall, fatigue at CTswim provides an ecologically relevant sub-lethal threshold that is more sensitive to extreme events than LOE at CTmax.

Effects of pH on the incubation and early development of fish species with different reproductive strategies.

Fish reproduction in natural environments tends to occur in conditions, including extreme pH values, ideal for the survival of offspring. In this context, the purpose of this study was to assess the influence of pH on both survival and early development of two fish species, Astyanax lacustris (short-distance migrating fish) and Piaractus mesopotamicus (long-distance migrating fish), with different reproductive strategies. Our experiments were divided into two tests (incubation and larviculture) at five pH levels. First was incubation through a water recirculation system using 2 L incubators followed by larviculture using a 2.5 L aquarium. pH had no influence on the hatching rate of A. lacustris eggs, but affected the yolk-sac diameter, while the newly-hatched larvae had some skeletal disorders. For P. mesopotamicus, pH influenced the hatching rate and perivitelline space, while the newly-hatched larvae had several skeletal disorders. The larviculture of A. lacustris revealed no effect on the survival rate, but the analyzed morphometric variables indicated significant differences between the treatments. An acidic pH negatively influenced the survival rate of P. mesopotamicus, and all morphometric variables also varied significantly between the treatments. We concluded that both the survival and development of A. lacustris and P. mesopotamicus revealed different responses at pH levels during incubation and larviculture tests.

ß-Glucan enhances respiratory activity of leukocytes suppressed by stress and modulates blood glucose levels in pacu (Piaractus mesopotamicus).

We evaluated the immune response of pacu fed with a ß-glucan diet (0.5%) for 10 days. After the feeding period, fish were subjected to handling and 3 h after, inoculated with Aeromonas hydrophila. Fish were sampled before handling (baseline condition), 3, 6, and 24 h and 1 week after inoculation. A higher level of blood glucose was found in fish treated with ß-glucan in baseline conditions. Handling and bacterial inoculation increased the circulating levels of cortisol and glucose and promoted the acute inflammatory response (lymphopenia and neutrophilia). ß-Glucan prevented the decrease in the respiratory activity of leukocytes observed in the control group at 3 h sampling. ß-Glucan did not affect the complement and lysozyme, which were activated 24 h after the bacterial challenge in control fish. A reduction in the number of leukocytes was found in fish treated with ß-glucan 1 week after the challenge. We suggest two plausible hypotheses for this event: (1) it could be attributed to a depletion of the immune responses or (2) it could be due to a mobilization of the leukocytes to the spleen for antigen presenting/processing. In general, ß-glucan avoided the reduction of the activity of leukocytes after stress and the bacterial challenge and increased the baseline glucose levels. Our findings confirm the immunomodulatory action of glucan and add evidence showing that glucan can have a role in stress response.

Oral administration of antibiotics increased the potential mobility of bacterial resistance genes in the gut of the fish Piaractus mesopotamicus.

BACKGROUND: Aquaculture is on the rise worldwide, and the use of antibiotics is fostering higher production intensity. However, recent findings suggest that the use of antibiotics comes at the price of increased antibiotic resistance. Yet, the effect of the oral administration of antibiotics on the mobility of microbial resistance genes in the fish gut is not well understood. In the present study, Piaractus mesopotamicus was used as a model to evaluate the effect of the antimicrobial florfenicol on the diversity of the gut microbiome as well as antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) using a metagenomic approach. RESULTS: The total relative abundance of ARGs and MGEs significantly increased during the antibiotic exposure. Additionally, phage integrases, transposases, and transposons flanking ARGs accumulated in the gut microbiome of P. mesopotamicus because of the antibiotic exposure. MGEs co-occurring with ARGs showed a significant positive correlation with the total ARGs found. Furthermore, shifts in the gut microbiome towards well-known putative pathogens such as Salmonella, Plesiomonas, and Citrobacter were observed following florfenicol treatment. Mainly Plesiomonas and Citrobacter harbored genes that code for multidrug and phenicol efflux pumps. Moreover, several genes related to RNA processing and modification, cell motility, SOS response, and extracellular structure were enriched due to the antibiotic application. The observed effects were visible during the complete application phase and disappeared at the post-exposure phase. CONCLUSIONS: Our findings suggest that the oral administration of antibiotics increases the potential for MGE-mediated exchange of ARGs in the gut of fish and could contribute to the enrichment and dispersion of ARGs in aquaculture systems. Importantly, this increase in the potential for ARGs exchange could be an effect of changes in community structure and/or ARG mobilization.

Viscera of fishes as raw material for extraction of glycosaminoglycans of pharmacological interest.

World fisheries and aquaculture production totaled 167 million tons in 2014. This high fish production generates a lot of waste that could be used as raw material for extraction of substances of pharmacological interest. In this work, we extract and characterize glycosaminoglycans (GAGs) present in the viscera of Nile tilapia (Oreochromis niloticus) and Pacu (Piaractus mesopotamicus), which are among the most vastly produced fishes in inland aquaculture in Brazil. Moreover, the anticoagulant activity of the GAGs fractions was evaluated. GAGs were obtained from total defatted viscera, after proteolysis, precipitation with ethanol, anion exchange chromatography and treatment with chondroitinase. Chondroitin sulfate (CS), dermatan sulfate (DS) and heparan sulfate (HS) were identified by agarose gel electrophoresis and NMR analyses. CS, DS and HS were identified in equivalent fractions obtained from both fishes, and all GAGs fractions showed anticoagulant activity.

Glutathione peroxidase and glutathione S-transferase in blood and liver from a hypoxia-tolerant fish under oxygen deprivation.

Liver enzyme activities can be employed as biomarkers, but liver can only be obtained with death of the specimen. On the other hand, blood withdrawal is a non-lethal procedure. Accordingly, the hypothesis of this study is to verify if glutathione peroxidase (GPX) and glutathione S-transferase (GST) activities in blood parallel those in the liver of the hypoxia-tolerant fish, Piaractus mesopotamicus (pacu), submitted to hypoxia conditions. GPX was assayed with H2O2 in cytosols from both liver and erythrocytes and exhibited no significant variation, either in erythrocytes or in liver, when comparing pacus under normoxia with those under hypoxia (42 h). GST activity with chloro-dinitrobenzene (CDNB), an artificial substrate suitable for almost all GST isoenzymes, was compared to activity with 4-hydroxy-nonenal (4-HNE), a physiological endogenous substrate. GST activity with CDNB did not change in liver or in erythrocyte cytosols in pacus under hypoxia compared to those under normoxia. On the other hand, a significant decrease in erythrocyte activity with 4-HNE was observed after 42 h of hypoxia in both erythrocytes and liver, which may be a response to increased lipid oxidation in erythrocytes. Erythrocyte GST activity was 3-fold higher with 4-HNE than with CDNB, indicating that 4-HNE is a more appropriate substrate to determine GST activity in pacu erythrocytes.

Weight and morphometric growth of Pacu (Piaractus mesopotamicus), Tambaqui (Colossoma macropumum) and their hybrids from spring to winter / Peso e crescimento morfométrico de pacu (Piaractus mesopotamicus), tambaqui (Colossoma macropumum) e seus híbridos da primavera ao inverno

This study aimed to evaluate weight and morphometric growth of the products of the complete diallel cross-breeding between pacu and tambaqui during the period from the end of spring to the beginning of winter. Was used 400 pacu, tambaqui, tambacu and paqui. 20 fish from each group were collected, weighed and submitted to morphometric evaluation every 28 days. The Logistic function adjusted better to describe the growth in body weight and the morphometric measures for age on all the genetic groups. The studied groups presented similar behavior of growth for body weight and morphometric measures. There were significant differences between the genetic groups regarding parameters A (asymptotic value) and B (integration constant) for body weight and for all the morphometric measures evaluated. For the parameter K (maturity rate), there were significant difference between groups for body weight, head length and body height. The groups possibly were affected the decrease of temperature. The Tambacu was superior to the Paqui in all the variables evaluated for the parameter A, and was also superior to the pure breed, except for head length and body width.(AU)

Este estudo teve como objetivo avaliar o peso e crescimento morfométrico dos produtos do cruzamento dialélico completo entre pacu e tambaqui. 20 peixes de cada grupo foram coletados, pesados e submetidos à análise morfométrica a cada 28 dias. O modelo que obteve o maior coeficiente de determinação e que melhor se ajuste ao método de Akaike foi verificado. A função logística foi ajustada para melhor descrever o crescimento do peso corporal e as medidas morfométricas para a idade em todos os grupos genéticos. Os quatro grupos estudados apresentaram comportamento semelhante para o peso corporal, bem como para as medidas morfométricas. Houve diferenças significativas entre os grupos genéticos sobre os parâmetros A (valor assintótico) e B (constante de integração) para o peso corporal e para todas as medidas morfométricas avaliadas. Para o parâmetro K (taxa de maturação), houve diferença significativa entre os grupos para o peso corporal, comprimento da cabeça e altura do corpo. Os grupos possivelmente foram afetados pela diminuição da temperatura. O tambacu foi superior ao Paqui em todas as variáveis avaliadas para o parâmetro A, e também foi superior para a raça pura, exceto para o comprimento e largura do corpo de cabeça.(AU)

Parasitism by Monogenoidea in Piaractus mesopotamicus (Characiformes, Characidae) cultivated in Paraná River (Brazil) / Parasitismo por Monogenoidea em Piaractus mesopotamicus (Characiformes, Characidae) cultivados no rio Paraná (Brasil)

Abstract This study investigated the occurrence, prevalence, mean abundance and mean intensity of monogenoidean parasites in Piaractus mesopotamicus farmed in cages in the reservoir of the Itaipu Hydroelectric Power Station, Paraná River, Brazil. The parasite distribution pattern and the correlation of prevalence and abundance with the total length of hosts were also investigated. Four monogenoidean species were collected: Anacanthorus penilabiatus, A. toledoensis, Mymarothecium ianwhitingtoni and M. viatorum. All the parasites collected in P. mesopotamicus showed the typical aggregated distribution pattern, and the abundance and the prevalence did not shown any correlation with the total length of hosts.

Resumo Neste estudo foi investigada a ocorrência, prevalência, abundância média e intensidade média de Monogenoidea parasitos de Piaractus mesopotamicus, cultivados em tanques-rede no reservatório da Usina Hidrelétrica de Itaipu, rio Paraná, Brasil. Foram investigados ainda o padrão de distribuição parasitária e a correlação entre a prevalência e abundância com o comprimento total dos hospedeiros. Quatro espécies de Monogenoidea foram coletadas: Anacanthorus penilabiatus, A. toledoensis, Mymarothecium ianwhitingtoni e M. viatorum. Todos os parasitos coletados em P. mesopotamicus apresentaram típico padrão de distribuição agregada e não foi observada correlação entre a abundância e a prevalência e o comprimento total dos hospedeiros.

Diet of fish (Characiformes: Characidae) during early developmental stages in the Upper Paraná river basin, Brazil / Alimentação de peixes (Characiformes: Charicidae) nas fases iniciais de desenvolvimento da bacia do Alto rio Paraná, Brasil

This study analyzed the diet during early developmental stages of Astyanax lacustris (AA), Piaractus mesopotamicus (PM), Megaleporinus obtusidens (MO) and Prochilodus lineatus (PL), under experimental conditions. Fish larvae, 350 of each species, were stocked separately in 16 fiber-cement tanks (500 L), from which, three larvae of each species were collected every three days, for 36 days. Tanks were fertilized (1.5 g NPK-7: 14: 8) and had 50% of the surface with macrophytes. Larvae were grouped in age classes = I: 5 to 11, II: 14 to 20, III: 23 to 29 and IV: 32 to 38 days and, dissected for analysis of the digestive tract. Methodologies of dominance, frequency of occurrence and points of food items were used. For AA and PM larvae, measurements were taken for the number and size of organisms to determine the percent participation in biovolume. Changes in diets of larvae in different age classes were found as well as between different species, with the same age. Rotifers were dominant in the content of digestive tracts of all species at Class I, and the larvae diets became more distinct with increasing age, in which AA consumed mainly rotifers, PM, larger organisms (mainly cladocerans), PL, algae (diatoms as the main item) and PP with a more diversified diet (rotifers, ostracodes and algae) . In conclusion, early stages of these species presented distinct diets, undergoing remarkable changes in the first 38 days of life.

Estudou-se a alimentação dos estágios iniciais de desenvolvimento de Astyanax lacustris (AA), Piaractus mesopotamicus (PM), Megaleporinus obtusidens (MO) e Prochilodus lineatus (PL) em condições experimentais. As larvas, 350 cada espécie, foram estocadas separadamente, em 16 tanques de fibrocimento (500 L) dos quais foram coletados três indivíduos de cada um, a cada três dias, por 36 dias. Os tanques foram fertilizados (1,5 g de NPK-7:14:8) e tinham 50% da superfície com macrófitas. As larvas foram agrupadas em classes de idade = I: 5 a 11, II: 14 a 20, III: 23 a 29 e IV: 32 a 38 dias e, dissecadas para a abertura do trato digestório. Foram empregadas as metodologias de dominância, frequência de ocorrência e pontos dos itens alimentares. Para as larvas de AA e PM, foram contados e tomadas medidas das dimensões dos organismos para determinar a participação percentual do biovolume. Observaram-se mudanças nas dietas das larvas em diferentes classes de idade e também entre larvas de espécies diferentes, com mesma idade. Houve predomínio de rotíferos nos conteúdos dos tratos digestórios de todas as espécies na classe I, as dietas das larvas passaram a ser mais distintas com o incremento da idade, com AA consumindo principalmente rotíferos, PM organismos maiores (principalmente cladóceros), PL tendo algas (diatomáceas como item principal) e PP com uma dieta mais variada (rotíferos, ostracodes e algas). Conclui-se que as formas jovens destas espécies apresentaram dietas distintas, passando por nítidas alterações nos primeiros 38 dias de vida.

Aloe vera enhances the innate immune response of pacu (Piaractus mesopotamicus) after transport stress and combined heat killed Aeromonas hydrophila infection.

In this study, pacu (Piaractus mesopotamicus) were fed with diets containing Aloe vera for 10 days prior to transport stress and infection with heat killed Aeromonas hydrophila. A. vera is popular around the world due to its medicinal properties, including immunostimulatory effects which was observed in this study. The results show that transport causes immunosuppression, an effect that was prevented by A. vera. Specifically, A. vera prevented reductions of both leukocyte respiratory burst and hemolytic activity of complement system caused by transport. Further, fish fed with A. vera also showed significantly higher leukocyte respiratory burst, serum lysozyme concentrations and activity of complement system 24 h after bacterial infection. Additionally, we observed that A. vera may modulate the innate response through activation of complement system during bacterial immune stimulation. In summary, A. vera extract enhanced innate immune parameters and consequently the ability of fish to cope with pathogens following transport stress. These findings show that A. vera has promise for use in aquaculture and add further evidence that medicinal herbs added to fish feed assist to prevent disease outbreaks.

Effects of Glyphosate-Based Herbicide Sub-Lethal Concentrations on Fish Feeding Behavior.

Glyphosate-based herbicides are widely used in agricultural systems. Although the target organism are particularly plant organisms, there are numerous studies showing adverse effects in aquatic animals, such as inhibition of acetyl cholinesterase, effects on kidney, liver, and gill and stressors effects. This study analyzed the effects of commercial formulation of glyphosate on feeding behavior in Pacu (Piaractus mesopotamicus). Fish were exposed to three glyphosate concentrations (0.2, 0.6, and 1.8 ppm) for 15 days. At concentrations of 0.2 and 0.6 ppm, food intake decreased on day 13 and then returned to normal on day 15. At the highest glyphosate-based herbicide concentration, 1.8 ppm, food consumption decreased dramatically and did not recover on day 15. This study showed that glyphosate-based herbicide at sub-lethal concentrations can affect feed intake in pacu and consequently inhibits its growth.

Impact of Brazilian fish species at early developmental stages on plankton communities and water chemical parameters / Impacto de espécies de peixes brasileiros em estágios iniciais de desenvolvimento sobre a comunidade planctônica e parâmetros químicos da água

Effect of larvae of Astyanax altiparanae (AA), Piaractus mesopotamicus (PM), Leporinus obtusidens (LO) and Prochilodus lineatus (PL) on plankton communities and water quality were evaluated. Twenty 500 L tanks were used into a completely randomized design with five treatments and four replications, containing 350 individuals of each species per tank. One treatment control had no larvae (CT). Every six days, were collected periphyton and water to determine the concentrations of chlorophyll and total phosphorus. Plankton samples (20 µm mesh net) were taken every three days. Fish affected plankton communities, which showed lower densities of total zooplankton in AA tanks than in LO tanks. Increased density of rotifers and reduced density of copepods were found in AA, PM and PL tanks in relation to the CT. Higher density of testate amoebae was observed in AA, PM and LO tanks. As to biovolume, higher values for total plankton were registered in the CT and LO tanks compared with AA, PM and PL tanks; higher values for rotifers were observed in PL tanks than in the CT. Copepod biovolume was higher in CT and LO tanks. Biovolume of cladoceran and testate amoebae were not affected. Plankton´s chlorophyll concentration was higher in tanks with fish. Higher concentrations of dissolved oxygen were found in AA and PM tanks. It can be concluded that juveniles of these fish species differently affect the plankton community and chemical parameters of the water.

Avaliou -se o efeito das fases iniciais de desenvolvimento de Astyanax altiparanae (AA), Piaractus mesopotamicus (PM), Leporinus obtusidens (LO) e Prochilodus lineatus (PL) nas comunidades planctônicas e a qualidade da água. Foram utilizados 20 tanques (500 L) em um delineamento inteiramente casualizado com cinco tratamentos e quatro repetições, onde foram estocados 350 indivíduos de cada espécie por tanque. Foi mantido um tratamento sem larvas (CT). A cada seis dias, foram retiradas amostras do perifíton e da água para determinar as concentrações de clorofila e do fósforo total. Foram realizadas coletas de plâncton (rede 20 µm) a cada três dias. Houve efeito dos peixes sobre a comunidade planctônica com menores densidades de zooplâncton total nos tanques com AA do que naqueles com LO. Observou-se aumento das densidades de rotíferos e redução das de copépodes nos tanques com AA, PM e PL em relação ao CT. Observaram-se maiores densidades de tecamebas nos tanques com AA, PM e LO. Observaram -se também valores superiores do biovolume para o plâncton total no CT e LO em comparação a AA, PM e PL, constatando-se maiores índices de rotíferos nos tanques com PL em relação ao CT. O biovolume dos copépodes foi mais elevado nos tanques CT e LO. O biovolume de cladóceros e tecamebas não foi afetado. A concentração de clorofila do plâncton foi maior nos tanques com peixes. Maiores teores de oxigênio dissolvido foram obtidos com AA e PM. Conclui-se que a presença das formas jovens dessas espécies de peixe afeta de forma diferenciada a comunidade planctônica e os parâmetros químicos da água.

Na2EDTA anticoagulant impaired blood samples from the teleost piaractus mesopotamicus / Anticoagulante Na2EDTA danifica amostras de sangue do teleósteo piaractus mesopotamicus

The present study aimed to evaluate the effects of Na heparin and Na2EDTA on blood of Piaractus mesopotamicus (360.7±42.4g, 26.4±1.0cm). Twenty fishes were sampled in two experiment trials, ten for erythrocyte fragility analysis and ten for hematologic and plasma biochemical study. The blood collected by venous-caudal puncture was fractioned and stored in anticoagulants solution: Na2EDTA 10%, Na2EDTA 3%, Na heparin 5000 IU and Na heparin 100 IU. Plasmatic levels of calcium presented in the Na2EDTA stored samples were about 80% lower than both heparin groups. Blood samples of P. mesopotamicus stored with Na2EDTA demonstrated increase in the hematocrit and MCV, and decrease in MCHC. The dose-response effect was observed in this study. The results are reinforced by the higher levels of plasmatic protein and hemolysis presented in the Na2EDTA 10% stored blood, confirming the deleterious effect of this anticoagulant treatment on the quality of blood samples. Na2EDTA is not indicated to store P. mesopotamicus blood samples, but sodium heparin at 100 IU is the most recommended anticoagulant, since this treatment presented the lower rate of alterations in the stored blood.

O presente estudo teve por objetivo avaliar os efeitos da heparina sódica e Na2EDTA no sangue de Piaractus mesopotamicus (360,7±42,4g, 26,4±1,0cm). Foram amostrados vinte peixes em dois ensaios experimentais, sendo dez peixes utilizados para análise da fragilidade dos eritrócitos e dez peixes para análise dos parâmetros hematológicos e estudo bioquímico do plasma. O sangue coletado por punção veno-caudal foi aliquotado e armazenado em diferentes soluções anticoagulantes: Na2EDTA 10%, Na2EDTA 3%, heparina sódica 5.000 UI e heparina sódica 100 UI. Níveis plasmáticos de cálcio apresentados nas amostras armazenados em Na2EDTA diminuíram cerca de 80% em relação aos dois grupos armazenados com heparina. Amostras de sangue de pacus armazenados com Na2EDTA demonstraram aumento do hematócrito e VCM, e diminuição na CHCM. O efeito dose-resposta foi observado neste estudo. Estes resultados são reforçados pelos níveis mais elevados de proteína plasmática e hemólise apresentado no sangue armazenado com Na2EDTA 10%, o que confirma o efeito deletério desse tratamento anticoagulante na qualidade de amostras de sangue. Na2EDTA não é indicada para armazenar amostras de sangue de P. mesopotamicus, e heparina sódica a 100 UI é o anticoagulante mais recomendado, uma vez que este tratamento apresentou a menor taxa de alterações no sangue armazenado.

Characterization of a new strain of Aeromonas dhakensis isolated from diseased pacu fish (Piaractus mesopotamicus) in Brazil.

This study provides a detailed description and characterization of a strain of Aeromonas dhakensis isolated from a diseased juvenile Piaractus mesopotamicus obtained from the fish farm of the National Center for Continental Fish Research and Conservation (CEPTA/ICMBio), in the state of São Paul, Brazil. Biochemical tests using the VITEK 2 automated bacterial identification system identified the isolate to genus level; however, further molecular analysis of the 16S rRNA, gyrB and rpoD genes showed that the strain belonged to the species A. dhakensis. As expected, the isolated A. dhakensis strain was resistant to ampicillin and ampicillin/sulbactam, as resistance to ampicillin is a typical characteristic of the genus Aeromonas. Resistance to cefoxitin and meropenem was also observed, but the strain was susceptible to most of the tested antibiotics. The isolated strain of A. dhakensis caused acute haemorrhagic septicaemia in experimentally infected P. mesopotamicus, with a fifty per cent lethal dose of 1.14 × 105  CFU/fish. This is the first report of the occurrence of an A. dhakensis strain causing an infection in a fish species of South America, providing important epidemiologic data relating to this important pathogenic species.

Essential oils to control ichthyophthiriasis in pacu, Piaractus mesopotamicus (Holmberg): special emphasis on treatment with Melaleuca alternifolia.

In vitro effect of the Melaleuca alternifolia, Lavandula angustifolia and Mentha piperita essential oils (EOs) against Ichthyophthirius multifiliis and in vivo effect of M. alternifolia for treating ichthyophthiriasis in one of the most important South American fish, Piaractus mesopotamicus (Holmberg), were evaluated. The in vitro test consisted of three EOs, each at concentrations of 57 µL L(-1) , 114 µL L (-1) , 227 µL L(-1) and 455 µL L (-1) , which were assessed once an hour for 4 h in microtitre plates (96 wells). The in vitro results demonstrated that all tested EOs showed a cytotoxic effect against I. multifiliis compared to control groups (P < 0.05). The in vivo treatment for white spot disease was performed in a bath for 2 h day(-1) for 5 days using the M. alternifolia EO (50 µL L (-1) ). In this study, 53.33% of the fish severely infected by I. multifiliis survived after the treatment with M. alternifolia (50 µL L (-1) ) and the parasitological analysis has shown an efficacy of nearly 100% in the skin and gills, while all the fish in the control group died. Furthermore, the potential positive effect of M. alternifolia EO against two emergent opportunistic bacteria in South America Edwardsiella tarda and Citrobacter freundii was discussed.

Growth, survival and bone alterations in Piaractus mesopotamicus larvae under different rearing protocols / Crescimento, sobrevivência e alterações ósseas em larvas de Piaractus mesopotamicus em diferentes protocolos de criação

The pacu (Piaractus mesopotamicus) is a neotropical freshwater fish. It is one of the most important species farmed in areas of the Parana and Paraguay Rivers basins. The effects of different rearing protocols on growth, survival and incidence of skeletal malformations in pacu larvae were analyzed. A total of six experimental treatments were considered, consisting of: a semi-intensive larviculture (L_S) in ponds; intensive larviculture (L_In) in laboratory (both L_S and L_In until 60 days of life); and mixed larviculture, with 20 days of semi-intensive larviculture into cages in ponds after 14 (L₁), 21 (L₂), 33 (L₃) or 40 (L₄) days of laboratory larviculture. At the end of the experimental period, L_Slarvae showed higher growth rate, with average weight values (2.28g) and total length (TL-48.20mm) statistically higher than the rest (P<0.05). L₁ to L₄ treatments showed intermediate growth values, without differences between them (P>0.05), while L_In presented the lowest growth (P<0.05). Survival was around 75% in all experimental groups, except L_S, that presented a significantly lower value (17.5%, P<0.05). Skeletal abnormalities were detected in all experimental treatments, but L_In and L₁ presented the lowest incidence. In no case, visible morphological alterations were found. This study shows that prolonging pacu rearing under laboratory conditions at high densities improves temporal availability and survival of juvenile without affecting growth or subsequent osteological development of fish.

O pacu (Piaractus mesopotamicus) é um peixe neotropical de água doce. É uma das espécies mais importantes cultivadas em áreas de bacias dos rios Paraná e Paraguay. Foi analisado o efeito da duração da larvicultura intensiva no crescimento, sobrevivência e incidência de malformações ósseas em pacu. Os tratamentos consistiram de uma larvicultura semi-intensiva (L_S) em viveiros, larvicultura intensiva no laboratório até 60 dias de idade (L_In), ou misto, com 20 dias de larvicultura semi-intensiva após 14 (L₁), 21 (L₂), 33 (L₃) e 40 (L₄) dias de larvicultura no laboratório. No final da experiência, as larvas do tratamento L_S apresentaram maior crescimento, com valores de peso médios (2,28g) e comprimento total (CT-48,20mm) estatisticamente superior ao resto (P<0,05). Os tratamentos L₁ a L₄apresentaram valores de crescimento intermediários, sem diferença estatística entre eles (P>0,05), enquanto L_In apresentaram os menores valores de crescimento estimados (P<0,05). A sobrevivência foi estimada em torno de 75% em todos os grupos, com exceção do L_S, o qual apresentou um valor mais baixo (17,5%, P<0,05). Em todos os tratamentos experimentais, foram detectadas alterações esqueléticas, mas em nenhum caso foi encontrado alteração morfológica visível. O presente estudo mostra que a retenção prolongada de larvas de pacu em alta densidade melhora a disponibilidade temporal e sobrevivência dos juvenis, sem afetar o crescimento ou desenvolvimento osteológico posterior destes.

Purification and physico-chemical study of serum albumins of two neotropical fish species from the São Francisco River Bassin, Brazil / Purificação e estudo físico-químico de albuminas de duas espécies de peixes neotropicais da Bacia do Rio São Francisco, Brasil

This paper presents results from a study of albumin from pacu (Piaractus mesopotamicus, Holmberg 1887) and the catfish pintado (Pseudoplatystoma corruscans, Spix & Agassiz, 1829), two neotropical fish species inhabitants of Brazilian rivers, comparing their molecular mass and discussing their secondary structures based on spectropolarimetric (circular dychroism) measurements. Genetic controlled specimens were obtained from two fish hatcheries, located in Mococa (pacu) and in São João da Boa Vista (pintado), both in São Paulo State, Brazil. After a period of adaptation in holding tanks, fish blood samples were taken by punctioning their abdominal aorta. Purified albumin was obtained by gel filtration. SDS-PAGE electrophoresis was performed for the molecular mass estimation. Circular Dichroism spectra were registered for albumins of the two fish species over the range of 190-250 nm (far-UV), which shown two negative bands at 217 and 208 nm, a positive peak at 196 nm and a crossover at 200 nm. This profile is compatible with proteins that content predominantly alpha-helix structure.

Este artigo apresenta os resultados de um estudo sobre as albuminas de pacu (Piaractus mesopotamicus, Holmberg 1887) e pintado (Pseudoplatystoma corruscans, Spix & Agassiz, 1829), duas espécies neotropicais de peixes nativas do Brasil, determinando as suas massas moleculares e discutindo suas estruturas secundárias, com base em medidas de espectropolarimetria (dicroísmo circular). Espécimes controlados geneticamente foram obtidos de duas diferentes pisciculturas, uma localizada na cidade de Mococa (pacu) e a outra, na cidade de São João da Boa Vista (pintado), ambas no Estado de São Paulo, Brasil. Após um período de adaptação em tanques apropriados, amostras de sangue foram coletadas por punção da aorta abdominal dos peixes. Albumina pura foi obtida por gel filtração dessas amostras e as massas moleculares foram determinadas a partir dos dados da eletroforese SDS-PAGE. Espectros de dicroísmo circular das albuminas dos peixes foram registrados na região de 190-250 nm (far-UV), os quais mostraram duas bandas negativas, a 217 e 208 nm, um pico positivo a 196 nm e um crossover a 200 nm; perfil este compatível com proteínas que contem predominantemente estrutura alfa-hélice.