Fish feed can show genotoxic damage.

The present study was carried out to evaluate the genotoxic potential of nutritional quality of feed, using erythrocytic nuclear abnormalities assay in Nile tilapia and its correlation with available nutrients and common fish growth biomarkers. For this, ten feeds commercialized in Brazil were assessed on digestibility and performance assays with triplicate groups. Venipuncture of the caudal vein for abnormalities analyzed was performed 102 days after the fish were fed with the commercial feed twice a day, to apparent satiation. Nuclear abnormalities were analyzed in blood smears. Principal component analysis and correlation matrix were used to carry out an exploratory analysis of correlation between frequency of abnormalities and performance parameters or available nutrients. The frequency of abnormalities in erythrocytes of Nile tilapia, fish performance, and digestibility were feed-dependent. It was observed correlations between the frequency of most abnormalities and performance parameters or content of nutrients. The frequency of kidney-shaped (6.23 ± 4.14), bud nuclei (2.99 ± 1.95), bridge nuclei (0.53 ± 0.50), and binuclei (0.43 ± 0.59) was the highest in fish that also presented the worst performance among all treatments and correlated with digestible methionine. Micronucleus frequency (0.33 ± 0.49) was higher in fish from the same group that presented depressed feed intake and lower available zinc. Only one group presented vacuolated nuclei and the frequency of this abnormality was correlated with available phosphorus. The frequency of abnormalities in erythrocytes is a fish sensitive indicator of health and plays an important role as a complementary tool in the assessment of fish feeding. The variation in the frequency of nuclear abnormalities in erythrocytes obtained among fish fed with the different feeds allows the assertion that they contained genotoxic factors.

Hepatic and gastroprotective activity of Serjania marginata leaf aqueous extract in Nile tilapia (Oreochromis niloticus).

The aim of this study was to assess the leaf aqueous extract composition of Serjania marginata and the effects of its inclusion on the diet of Nile tilapia (Oreochromis niloticus), with respect to the activity of digestive enzymes and enzymes associated with the metabolism of the liver and intestine and liver histopathology. Fish (initial mean weight, 54.36 ± 17.04 g) were divided into groups: fasting (without feeding), control (commercial feed), and treatment (commercial feed with leaf aqueous extract of Serjania marginata), and in each aquarium, there were five individuals and the fish fed ad libitum for 15 days. Treatment fish had ingested on average 224.3 mg of extract/kg of fish/day. In the extract analysis by mass spectrometry, quercitrin, isoquercitrin, A-type proanthocyanidin trimer, and quinic acid were identified. In the enzymatic activity, fish from the treatment group showed higher level of alkaline phosphatase, while the hepatotoxic markers (AST and ALT) and levels of lipase, amylase, and nonspecific protease did not differ (p > 0.05). In liver histopathological analysis, it was observed that fish from the treatment showed normal structure, while abnormalities were associated with control (fibrosis, loss of cordonal architecture, vacuolated hepatocytes with nucleus displaced to the periphery) and fasting (reduction in hepatocyte size and sinusoidal space). The intestine histopathology evidenced that the extract favored the development of goblet cells and intestinal fold height. The results indicated that the leaf aqueous extract of S. marginata assists in the structural maintenance of the liver and intestine and stimulates intestinal alkaline phosphatase production in Nile tilapia, suggesting that the identified compounds act on the liver and intestine, showing hepatoprotective effects and stimulating intestinal digestion.

Clove oil induces anaesthesia and blunts muscle contraction power in three Amazon fish species.

Clove oil is used as an anaesthetic for many species of fish worldwide; however, relatively few studies have assessed its effectiveness on Amazon fish species and no compelling evidence has ever been reported on the relaxant properties of this oil for skeletal muscle of fish. Thus, the objective of this study was to evaluate the latencies to deep anaesthesia and recovery, along with the myorelaxant effect of clove oil on three Amazon fish species: cardinal tetra, Paracheirodon axelrodi, banded cichlid, Heros severus and angelfish, Pterophyllum scalare, submitted to short-term anaesthetic baths. Fish were assayed in three groups of 60 fish each and individually anaesthetized in a completely randomized design with six clove oil concentrations using 10 fish/species/concentration. Electromyographic recordings from dorsal muscle were performed during stages of induction and recovery in which nine fish/species/stage were used. Deep anaesthesia was attained for all concentrations tested, and no mortalities were observed throughout the experiments and after a 48-h observation period. Concentration of 90 µL L-1 and above promoted fast deep anaesthesia (< 3 min) and calm recovery in angelfish and cardinal tetra, whereas the concentration of 60 µL L-1 sufficed to quickly anaesthetize banded cichlid. Times to full recovery were not significantly contrasting among species and occurred within appropriate time threshold (< 5 min). Clove oil exerted a conspicuous depression of muscle contraction power, and therefore can be effectively used as a muscle relaxant agent for P. scalare, P. axelrodi, H. severus and potentially, for other fish species.

Myxobolus sp. (Myxozoa) in the circulating blood of Colossoma macropomum (Osteichthyes, Characidae).

Myxosporea parasitize many organs in fresh and saltwater fish. Species of the genus Myxobolus parasitizing the gills and other organs of the tambaqui Colossoma macropomum have been described. In the present study, blood smears were made from juvenile tambaqui and were stained with May Grunwald-Giemsa-Wright in order to identify myxozoan parasites. Out of a total of 36 fish examined, one specimen (2.7%) that was reared in a cage presented spores that were identified as M. colossomatis, whereas fish kept in 250 L tanks showed prevalence of 5.5%. This is the first report of M. colossomatis in the blood of farmed tambaqui in the Amazon region. These results indicate that myxozoan parasites should also be investigated in fish blood smears. Some myxosporean species may cause diseases in fish, and these species need to be identified so that adequate preventive sanitary control can be instituted.

Myxobolus sp. (Myxozoa) in the circulating blood of Colossoma macropomum (Osteichthyes, Characidae) / Myxobolus sp. (Myxozoa) no sangue circulante de Colossoma macropomum (Osteichthyes, Characidae)

Myxosporea parasitize many organs in fresh and saltwater fish. Species of the genus Myxobolus parasitizing the gills and other organs of the tambaqui Colossoma macropomum have been described. In the present study, blood smears were made from juvenile tambaqui and were stained with May Grunwald-Giemsa-Wright in order to identify myxozoan parasites. Out of a total of 36 fish examined, one specimen (2.7 percent) that was reared in a cage presented spores that were identified as M. colossomatis, whereas fish kept in 250 L tanks showed prevalence of 5.5 percent. This is the first report of M. colossomatis in the blood of farmed tambaqui in the Amazon region. These results indicate that myxozoan parasites should also be investigated in fish blood smears. Some myxosporean species may cause diseases in fish, and these species need to be identified so that adequate preventive sanitary control can be instituted.

Mixosporídeos parasitam diversos órgãos de peixes de água doce e salgada, tendo sido descrita espécie do gênero Myxobolus parasitando brânquias e outros órgãos de tambaqui Colossoma macropomum. No presente trabalho, extensões sanguíneas de juvenis de tambaquis foram confeccionadas e coradas com May Grunwald-Giemsa-Wright para identificação de parasitos myxozoários. Do total de 36 peixes examinados, um espécime (2,7 por cento) cultivado em tanque-rede apresentou esporos identificados como M. colossomatis, enquanto os peixes mantidos em tanques com 250 L apresentaram prevalência de 5,5 por cento. Esse é o primeiro registro de M. colossomatis no sangue de tambaqui cultivado na Amazônia. Esses resultados indicam que parasitos Myxozoa devem ser também investigados em extensões sanguíneas. Algumas espécies de mixosporídeos podem causar doença em peixes, sendo necessária a identificação da espécie para um adequado manejo sanitário preventivo.

Avaliação de respostas metabólicas do tambaqui exposto ao eugenol em banhos anestésicos / Evaluation of tambaqui metabolic responses to eugenol in anesthetics baths

O tambaqui é a principal espécie de peixe cultivado na Amazônia Ocidental. Porém durante o processo produtivo, práticas de manejo são necessárias para o monitoramento do crescimento e estado geral da sanidade dos animais. Para isso os animais devem ser anestesiados para maior segurança no trabalho. O eugenol, componente majoritário do óleo de cravo, tem sido bastante utilizado como anestésico alternativo para peixes por ser um produto natural e de baixo custo. Entretanto, estudos tratando de respostas metabólicas em peixes tropicais expostos a diferentes anestésicos são ainda necessários. Dentro desse intuito, o presente trabalho avaliou respostas metabólicas, detectadas por meio de alterações de parâmetros sanguíneos e plasmáticos do tambaqui, exposto ao eugenol em banhos anestésicos simulados. Respostas típicas ao estresse foram detectadas devido ao manuseio imposto aos peixes durante a realização dos banhos anestésicos. O eugenol não reduziu totalmente essas reações ao estresse. Por outro lado, esse anestésico não provocou estresse adicional em exposições curtas de 15 min em concentrações próximas a 20 mg L-1.

Tambaqui is the main farmed fish in the Western Amazon. However, in handling this fish has to be anesthetized for safety purposes, usually when evaluating growth and health conditions. Eugenol, the main component of clove oil, has been reported as an alternative fish anesthetic, because it is an inexpensive natural product. However, continued studies are necessary about the metabolic responses of tropical fish to anesthetics. The present work evaluated metabolic responses of tambaqui to eugenol in simulated anesthetic baths, measuring blood and plasma parameters. Typical metabolic stress responses to handling were detected, but they were not totally reduced by eugenol. On the other hand, the anesthetic dissolved in water did not provoke any extra charge of stress during short-term exposures in concentrations of about 20mg L-1 for 15 min.

Anestesia do pirarucu por aspersão da benzocaína diretamente nas brânquias / Anesthesia in pirarucu by benzocaine sprays in the gills

O pirarucu (Arapaima gigas) é um peixe que pode atingir mais de 2m e 100kg. No entanto, por ser um animal de grande porte, o risco de acidentes é bastante elevado durante o manejo. Logo, anestésicos são essenciais para segurança no trabalho. Nesse contexto, estudou-se a possibilidade do uso da benzocaína aspergida diretamente nas brânquias do pirarucu, para indução à anestesia do peixe pulmonado da Amazônia sem riscos de afogamento. Foram testadas as concentrações de 25, 50 e 75mg L-1 em indivíduos adultos (55,1±7,0kg e 1,80±0,1m) e as concentrações de 50 e 100mg L-1 em juvenis (6,0±0,6kg e 87,2±5,6cm). Os resultados mostram viabilidade do uso da benzocaína aspergida diretamente nas brânquias do pirarucu em concentrações de 50 a 100mg L-1, proporcionando anestesia com ausência de movimentação por aproximadamente 2min, tempo suficiente para procedimentos rápidos, como biometria, injeções, marcação, coleta de raspados de muco na superfície do corpo e brânquias. Mortalidade de animais não foi observada mesmo um mês após os testes.

Pirarucu (Arapaima gigas) is a fish that may achieve more than 2m and 100kg. Thus handling of this fish may impose risks to workers. In this way, anesthetics are imperative for safety at work, but usual anesthetics baths are not feasible for pirarucu because of the fish size and the species pulmonary respiration. Pirarucu may die drowned if submersed as the other fishes in anesthetics baths. Therefore, this work tested the possible use of benzocaine directly sprinkled in the gills of pirarucu. In the first experiment, benzocaine solutions in concentrations of 25, 50 and 75mg L-1 were tested for adult fish (55.1±7.0kg e 1.80±0.1m). In the second one, the anesthetic in concentrations of 50 and 100mg L-1 were tested for juveniles (6.0±0.6kg e 87.2±5.6cm). Benzocaine sprinkled directly in the gills of pirarucu showed to be an efficient anesthetic both for juveniles and adult fish. It was observed absence of movements during 2min, time enough for most handling procedures. No mortality occurred even one month after experiments.

Anestesia do pirarucu por aspersão direta nas brânquias do eugenol em solução aquosa / Anesthesia in pirarucu by eugenol sprays in the gills

O pirarucu (Arapaima gigas) é um peixe que vem ganhando importância cada vez maior na piscicultura comercial na Amazônia. No entanto, por ser um animal de grande porte, no campo, é comum o relato de acidentes envolvendo pancadas violentas em técnicos durante o manejo. Desse modo, é imperativa a anestesia desses animais. Todavia, para a espécie em discussão, a realização de banhos anestésicos, muitas vezes, não é possível devido ao tamanho do animal e ao risco de afogamento do peixe pulmonado. O presente trabalho avaliou de maneira prática a viabilidade do eugenol como anestésico para o pirarucu por aspersão direta nas brânquias. Para tanto, três animais jovens foram submetidos à aspersão de eugenol nas brânquias em concentração de 30mg L-1 e dois na concentração de 60mg L-1. O eugenol borrifado nas brânquias mostrou-se viável como anestésico para o pirarucu, não sendo observada a mortalidade de animais mesmo um mês após os testes.

Pirarucu (Arapaima gigas) is an important species to commercial fish farming in Amazon. It achieves more than 2m and 100kg. However, fish handling may be risky to workers. Anesthesia is necessary, but usual anesthetic baths are not feasible due to the size of fish and the pulmonary respiration of Pirarucu. This fish may die drowned in anesthetic baths. This research evaluated the alternative anesthetic eugenol to pirarucu by sprays in the gills. Solution in concentration of 30mg L-1 was sprinkled in the gills of three fish, and 60mg L-1 was sprinkled in the gills of two other fish. Eugenol sprays provided safe anesthesia for pirarucu. No mortality was observed even one month after the experiment.

Physiological stress responses in the warm-water fish matrinxã (Brycon amazonicus ) subjected to a sudden cold shock / Respostas fisiológicas ao estresse do peixe de águas tépidas matrinxã (Brycon amazonicus ) submetido à queda brusca de temperatura

The present work evaluated several aspects of the generalized stress response [endocrine (cortisol), metabolic (glucose), hematologic (hematocrit and hemoglobin) and cellular (HSP70)] in the Amazonian warm-water fish matrinxã (Brycon amazonicus ) subjected to an acute cold shock. This species farming has been done in South America, and growth and feed conversion rates have been interesting. However, in subtropical areas of Brazil, where the water temperature can rapidly change, high rates of matrinxã mortality have been associated with abrupt decrease in the water temperature. Thus, we subjected matrinxã to a sudden cold shock by transferring the fish directly to tanks in which the water temperature was 10ºC below the initial conditions (cold shock from 28ºC to 18ºC). After 1h the fish were returned to the original tanks (28ºC). The handling associated with tank transfer was also imposed on control groups (not exposed to cold shock). While exposure to cold shock did not alter the measured physiological conditions within 1h, fish returned to the ambient condition (water at 28º C) significantly increased plasma cortisol and glucose levels. Exposure to cold shock and return to the warm water did not affect HSP70 levels. The increased plasma cortisol and glucose levels after returning the fish to warm water suggest that matrinxã requires cortisol and glucose for adaptation to increased temperature.

O presente trabalho avaliou as principais respostas fisiológicas e celulares [endócrino (cortisol), metabólico (glicose), hematológico (hematócrito and hemoglobina) e celular (HSP70)] ao estresse de um peixe de águas tépidas, o matrinxã (Brycon amazonicus ), quando submetido a um choque térmico frio abrupto. Essa espécie vem sendo amplamente cultivada na América do Sul por apresentar excelentes índices zootécnicos de crescimento e conversão alimentar. Entretanto, os produtores rurais encontram limitações no manejo do matrinxã, quando criado em regiões mais frias que sua região de origem, a Bacia Amazônica. Assim, o matrinxã foi submetido a um choque frio através da transferência direta dos peixes para tanques com água fria a 18ºC. Após 1h, esses peixes retornaram a suas caixas de origem a 28ºC. O manuseio de peixes necessário para conduzir o choque térmico experimental foi também imposto aos grupos controle, sendo, entretanto, evitada a água fria. O matrinxã demonstrou claros sinais de estresse fisiológico durante os procedimentos experimentais. Porém, essas respostas não foram associadas ao choque frio, mas sim ao choque quente por ocasião da volta dos peixes para as caixas de origem. As respostas primárias e secundárias de estresse foram evidentes através das análises plasmáticas de cortisol e glicose. Já o hematócrito, a hemoglobina e as expressões da proteína de estresse, HSP70, não foram afetadas. Nossos resultados sustentam que o matrinxã falhou em responder ao choque térmico frio, mas não ao choque térmico quente, que é um estressor evidentemente associado à origem natural dessa espécie de águas de elevadas temperaturas.

Effects of clove oil on the stress response of matrinxã (Brycon cephalus) subjected to transport

O transporte de peixes vivos é certamente um dos principais estímulos adversos à homeostase dos peixes nas condições de criação em cativeiro. O presente trabalho mensurou o estresse do matrinxã (Brycon cephalus), quando submetido ao transporte em sacos plásticos, bem como avaliou os efeitos do uso do anestésico óleo de cravo nessa etapa do manejo. Foram testadas as concentrações de 0, 1, 5 e 10 mg/L de óleo de cravo em bolsas plásticas preenchidas com água e oxigênio, de acordo com as práticas comumente utilizadas no Brasil. O óleo de cravo reduziu algumas das principais respostas ao estresse (cortisol, glicose plasmática e íons) mensuradas. O alto gasto de energia para o matrinxã tolerar o transporte foi evidenciado pela diminuição dos valores de glicogênio hepático. Os resultados sugerem que o óleo de cravo em concentração de 5 mg/L pode atenuar as principais respostas de estresse do matrinxã durante o transporte.

Standardization of 2-phenoxyethanol as anesthetic for juvenile Brycon cephalus (Gunther, 1869): the use in field procedures

Em muitos procedimentos de campo que englobam a manipulação de peixes vivos, os animais sofrem grandes riscos de se machucarem devido aos excessivos movimentos que realizam fora da água, sendo necessária a contenção dos animais através do uso de anestésicos. O 2-phenoxyethanol é um produto químico amplamente utilizado no país, sendo, entretanto ainda necessários mais estudos a respeito das respostas fisiológicas dos peixes tropicais às suas propriedades anestésicas. O presente trabalho avaliou o tempo de indução à anestesia de juvenis de matrinxã submetidos a oito diferentes concentrações de 2-phenoxyethanol. O tempo de indução à anestesia diminuiu em função das concentrações do anestésico testado no intervalo de 250-600mg litro-1. Os peixes foram anestesiados com segurança após um minuto, em banhos de 2-phenoxyethanol em concentração superior a 400mg litro-1. O período de recuperação dos animais foi de aproximadamente um minuto para todas as concentrações testadas. O 2-phenoxyethanol é um anestésico seguro para juvenis de matrinxã mesmo em elevadas concentrações até 600mg litro-1.

Clove oil as anaesthetic for juveniles of matrinxä Brycon cephalus (Gunther, 1869)

Many chemicals have been used as anaesthetics in fish farms and fish biology laboratories to keep the fish immobilized during handling procedures and to prevent accidents and animal stress. In Brazil, tricaine methane sulfonate (MS 222), quinaldine sulfate, benzocaine, and phenoxyethanol are the most common fish anaesthetics used to prevent fish stress during handling, but many side effects such as body and gill irritations, corneal damage and general risks of intoxication have been reported. Clove oil is a natural product proposed as an alternative fish anaesthetic by many researchers and it has been used in many countries with great economic advantages and no apparent toxic properties. In this work, we assessed the suitability of clove oil to anaesthetize matrinxä. Sixty-three juveniles of matrinxä were exposed to seven anaesthetic batches of clove oil (pharmaceutical grade) namely 18, 20, 30, 40, 50, 60, and 70 mg/L. The times to reach total loss of equilibrium and to recover the upright position were measured. Clove oil concentration about 40 mg/L was enough to anaesthetize the fish in approximately one minute and the recovery time was independent in regard to anaesthetic concentration