Abstract Brazil has five climatically distinct regions, with an annual average temperature difference up to 14 ºC between the northern and southern extremes. Environmental variation of this magnitude can lead to new genetic patterns among farmed fish populations. Genetically differentiated populations of tambaqui (Colossoma macropomumCuvier, 1818), an important freshwater fish for Brazilian continental aquaculture, may be associated with regional adaptation. In this study, we selected tambaquis raised in two thermally distinct regions, belonging to different latitudes, to test this hypothesis. De novo transcriptome analysis was performed to compare the significant differences of genes expressed in the liver of juvenile tambaqui from a northern population (Balbina) and a southeastern population (Brumado). In total, 2,410 genes were differentially expressed (1,196 in Balbina and 1,214 in Brumado). Many of the genes are involved in a multitude of biological functions such as biosynthetic processes, homeostasis, biorhythm, immunity, cell signaling, ribosome biogenesis, modification of proteins, intracellular transport, structure/cytoskeleton, and catalytic activity. Enrichment analysis based on biological networks showed a different protein interaction profile for each population, whose encoding genes may play potential functions in local thermal adaptation of fish to their respective farming environments.

Abstract The present study aimed to evaluate the biological responses of Colossoma macropomum to naphthalene injection and subsequent hypoxia exposure, emphasizing the expression of the tumor suppressor gene tp53. Tambaquis were intraperitoneally injected with naphthalene (50 mg/kg) and, after 96 hours, the fish were transferred to respirometry chambers and, submitted to progressive hypoxia for the determination of critical PO2. In a subsequent experiment, the fish received an intraperitoneal injection of naphthalene and were kept for 96 hours under normoxia. Successively, fish were challenged with acute hypoxia (PO2<PO2 crit) during 6 hours. We observed that the PO2 crit was not affected by naphthalene injection. Moreover, hematological parameters were modulated only in response to hypoxia. Fish with naphthalene injection plus hypoxia exposure presented altered activity of the GST and CAT enzymes. Exposure to naphthalene also resulted in DNA damages, which was not influenced by hypoxia. Hypoxia accentuated the hepatic lesions caused by naphthalene, as well as it also impaired the transcription of tp53 in naphtalene injected fish, demonstrating the risks of contaminating aquatic environments, especially environments where hypoxic conditions are common and occur on a daily or on seasonal basis, as in the Amazon basin.

Abstract Two Amazonian closely related tetras – cardinal Paracheirodon axelrodi and green neon P. simulans – were artificially acclimatized to environmental chambers mimicking future climate change scenarios (mild, moderate and extreme), using a microcosm facility. P. simulans survived (100%) to all scenarios after 30 days exposure, while P. axelrodi presented decreasing survival percentages according to environmental severity. These differences may be the reflection of distinct natural acclimatization to microhabitats between the species, which differ in thermal conditions. Survival responses might be related to differences in relative gene expression of lactate dehydrogenase (Ldh), suggesting that P. axelrodi anaerobic potential is lower or non-existent compared to P. simulans, not tolerating long-term thermal challenges. Accordingly, increases in temperature and in CO2 levels caused increases in energy demand and resulted in activation of the anaerobic pathway, as demonstrated by the higher enzyme levels measured in head and tail portions of both species. Sustained anaerobic glycolysis is possible when fish live in challenging environments (low oxygen or high temperature). Our results clearly show that P. simulans has a larger scope for survival to higher energy demands due to its increased anaerobic potential compared to P. axelrodi.

Abstract Benzo[a]pyrene (B[a]P) is a petroleum derivative capable of inducing cancer in human and animals. In this work, under laboratory conditions, we analyzed the responses of Colossoma macropomum to B[a]P acute exposure through intraperitoneal injection of four different B[a]P concentrations (4, 8, 16 and 32 μmol/kg) or corn oil (control group). We analyzed expression of the ras oncogene and the Hypoxia-inducible factor-1 alpha (hif-1α) gene using quantitative real-time PCR. Additionally, liver histopathological changes and genotoxic effects were evaluated through the comet assay. Ras oncogene was overexpressed in fish exposed to 4, 8 of 16 μmol/kg B[a]P, showing 4.96, 7.10 and 6.78-fold increases, respectively. Overexpression also occurred in hif-1α in fish injected with 4 and 8 μmol/kg B[a]P, showing 8.82 and 4.64-fold increases, respectively. Histopathological damage in fish liver was classified as irreparable in fish exposed to 8, 16 and 32 μmol/kg μM B[a]P. The genotoxic damage increased in fish injected with 8 and 16 μmol/kg in comparison with the control group. Acute exposure of B[a]P was capable to interrupt the expression of ras oncogene and hif-1α, and increase DNA breaks due to tissue damage.

A inevitável manipulação de peixes vivos em piscicultura causa uma série de reações fisiológicas adversas, o que exige o uso de anestésicos. O objetivo foi avaliar a eficiência do óleo de cravo como anestésico para juvenis avançados (aproximadamente 55 g e 13 cm) de tilápia do Nilo durante o manejo. No primeiro experimento, os peixes foram expostos a banhos anestésicos em seis diferentes concentrações (80; 100; 150; 200; 250 e 300 mg L-1) e foi avaliado o tempo de indução aos diferentes estágios de anestesia. No segundo experimento, avaliaram-se os diferentes tempos de exposição à anestesia, sendo verificada a margem de segurança do anestésico. Por último, avaliaram-se as respostas de estresse após a anestesia em 250 mg L-1. Os parâmetros avaliados foram cortisol, glicose, hematócrito, hemoglobina e níveis plasmáticos de sódio e potássio. A concentração 250 mg L-1 de óleo de cravo foi a mais adequada para indução de anestesia cirúrgica. Para a anestesia voltada para biometria e breve manejo, a concentração mais adequada foi 150 mg L-1. A exposição à concentração ideal de óleo de cravo por 10 min., não causou estresse severo, ocorrendo alterações após a anestesia somente nos níveis de glicose e hematócrito.

Handling of live fish is inevitable in fish farms and causes a number of adverse physiological reactions, thus requiring the use of anesthetics. The main goal of the present work was to evaluate the efficiency of clove oil as an anesthetic for juvenile tilapia (approximately 55 g and 13 cm) during handling. In the first experiment, fishes were exposed to an anesthetic bath at six concentrations (80, 100, 150, 200, 250 and 300 mg L-1). Subsequently, the induction time was assessed for different stages of anesthesia. In the second experiment, different times of exposure to anesthesia were tested, aiming to assess the safety margin of the anesthetic. Finally, we evaluated the responses to stress after exposure to 250 mg L-1 anesthesia. The following parameters were tested: cortisol, glucose, hematocrit, hemoglobin, and plasma sodium and potassium levels. The concentration of 250 mg L-1 of clove oil is the most appropriate to induce surgical anesthesia, and 150 mg L-1 for biometrics and brief handling. Anesthesia at the ideal concentration for 10 minutes did not result in severe stress. Only blood glucose and hematocrit were affected after anesthesia.

Adaptation or acclimation to hypoxia occurs via the modulation of physiologically relevant genes, such as erythropoietin, transferrin, vascular endothelial growth factor, phosphofructokinase and lactate dehydrogenase A. In the present study, we have cloned, sequenced and examined the modulation of the LDH-A gene after an Amazonian fish species, Astronotus crassipinis (the Oscar), was exposed to hypoxia and anoxia. In earlier studies, we have discovered that adults of this species are extremely tolerant to hypoxia and anoxia, while the juveniles are less tolerant. Exposure of juveniles to acute hypoxia and anoxia resulted in increased LDH-A gene expression in skeletal and cardiac muscles. When exposed to graded hypoxia juveniles show decreased LDH-A expression. In adults, the levels of LDH-A mRNA did not increase in hypoxic or anoxic conditions. Our results demonstrate that, when given time for acclimation, fish at different life-stages are able to respond differently to survive hypoxic episodes.

Foram estudados hemolisados de 22 espécies de peixes coletados na Ilha da Marchantaria (rio Solimões, Manaus - AM), através de eletroforeses em gel de amido e gel de ágar-amido. Uma grande heterogeneidade hemoglobínica interespecífica foi detectada, a exemplo do observado para espécies de zona subtropical e temperada. A capacidade de resolução de dois suportes eletroforéticos é discutida. Os resultados são discutidos em função da possível adaptabilidade conferida pelos sistemas de múltiplas hemoglobinas.

The hemoglobin patterns of hemolysates from 22 fish species belonging to Manchantaria island (Solimões river , Manaus, AM) had been characterized by starch gel and agarstarch gel electrophresis. High interespecific hemoglobin heterogeneity was observed, similarly to those described for sub-tropical and temperate fish species. The resolution power of the electrophoretic supports was considered. The adaptability question of the multiple hemoglobin systems was regarded.