Adaptações metabólicas dos ciclídeos aos ambientes hipóxicos da Amazônia

Os ciclídeos neotropicais são teleósteos avançados e distribuem-se pela África, Madagascar, Américas Central e do Sul, México, sul da Índia e Sri Lanka. Em trabalhos recentes, foi sugerido que esta família está distribuída no ambiente natural de acordo com sua capacidade de tolerância a hipóxia. Diante disso, os principais objetivos dessa tese foram: 1) Verificar a atividade e a expressão da enzima Lactato Desidrogenase (LDH; E.C. 1.1.1.27) de três espécies de ciclídeos da Amazônia Central relacionando a atividade e a expressão da LDH com a disponibilidade de oxigênio no ambiente natural; 2) comparar o perfil metabólico de várias espécies de ciclídeos coletadas na natureza; e 3) verificar os ajustes metabólicos em duas espécies de ciclídeos expostas a hipóxia gradual. O primeiro objetivo foi alcançado acompanhando a variação da atividade da enzima LDH, assim como a expressão dessa enzima no músculo branco e cardíaco em três espécies de ciclídeos, Satanoperca aff. jurupari, Heros apendiculatus e Chaetobrancopsis orbicularis, durante um ano de coleta nas proximidades do Lago CatalãoManaus. Os resultados obtidos mostraram que a atividade da enzima LDH no músculo cardíaco das três espécies tem correlação com a quantidade de oxigênio dissolvido no meio, ou seja, à medida que a concentração de oxigênio diminui no meio a atividade da LDH aumenta no coração. Apenas a isozima A4 foi expressa tanto no músculo branco quanto no coração. Esses resultados revelam alguns dos ajustes que estas espécies desenvolveram para sobreviver aos ambientes hipóxicos da Amazônia. O segundo objetivo foi alcançado estudando o perfil metabólico de nove espécies de ciclídeos coletadas no período de outubro e novembro de 2000, também na região do Lago CatalãoManaus. Para caracterizar o perfil metabólico dessas espécies foram avaliadas as atividades das seguintes enzimas: Piruvato Kinase (PK; E.C. 2.7.40), LDH (1 e 10mM), Malato Desidrogenase (MDH; E.C. 1.1.1.37) e 3-Hidroxiacil CoA Desidrogenase (HOAD; E.C. 1.1.1.35) nos músculos branco e cardíaco, fígado e cérebro, e ainda avaliamos o conteúdo de glicogênio hepático e muscular. Analisando os resultados obtidos podemos dizer que há uma similaridade na atividade das enzimas nas nove espécies de ciclídeos aqui estudadas e no conteúdo de glicogênio. Observamos também que o metabolismo de todos os tecidos estudados, das nove espécies, está baseado na glicólise. As taxas da HOAD (metabolismo dos lipídeos) foram bem menores que das enzimas glicolíticas. Estes resultados são consistentes com os da literatura, onde os animais tolerantes a hipóxia baseiam seu metabolismo, preferencialmente, no metabolismo glicolítico e apresentam uma redução do metabolismo oxidativo baseado na combustão dos ácidos graxos. Quanto ao terceiro objetivo, duas espécies de ciclídeos, Astronotus crassipinnis e Symphysodon aequifasciatus (n=10) foram expostas a hipóxia gradual, ou seja, em diferentes tensões de oxigênio (6,0, 3,0, 1,5, 0,75, 0,6, 0,3 e 0,0 mgO2L), durante 8 horas. A espécie A. crassipinnis sobreviveu a todas essas concentrações, sendo tolerante em ausência total de oxigênio (0,0 mgO2L) por mais de 2,5h, demonstrando ser altamente tolerante a hipóxia e a anóxia. Por outro lado, a espécie S. aequifasciatus resistiu no máximo 4,5h na tensão de 0,6 mgO2L, sendo considerada então moderadamente tolerante a hipóxia severa. Ambas as espécies apresentaram aumento nos batimentos operculares e diminuição do consumo de oxigênio quando expostas a condições hipóxicas. Observou-se, também, aumento nos níveis de glicose e lactato plasmáticos quando as espécies foram expostas a concentrações inferiores a 0,75 mgO2L. Em ambas as espécies, a concentração de glicogênio hepático apresentou-se reduzida, enquanto que no músculo branco houve aumento no conteúdo de glicogênio. Quanto à atividade das enzimas, a maioria sofreu alteração durante a exposição das duas espécies nas diferentes tensões de oxigênio. Com base nesses resultados concluimos que ambas as espécies baseiam sua tolerância a hipóxia em combinação com a glicólise anaeróbica. Como conclusão geral podemos dizer que as espécies de ciclídeos possuem diversas estratégias de sobrevivência para lutar com os ambientes hipóxicos da Amazônia, sendo assim pode-se dizer que a maioria delas é tolerante a hipóxia

Transportation of juvenile tambaqui (Colossoma macropomum) in a closed system

The objective of this study was to investigate the effect of density, duration and the use of additives to the water during the transportation of juvenile tambaqui (Colossoma macropomum) and use of this data to establish a safe transportation protocol for the species. The tested products and dosages were: salt (1000, 2000 and 3000 mg/L), gypsum (100, 300 and 500 mg/L) and benzocaine (10, 20 and 30 mg/L). Fish were transported in closed systems (plastic bag) at different densities and time periods of up to 24 h. Fish survival (FS) and water quality parameters were monitored immediately after transportation. The remaining fish were kept in floating cages in order to evaluate mortality which occurred up to 96 h after transportation (S96). The best fish density, additives dosages and time period of the transportation was estimated with a general linear model. The effect of the condition factor on FS and S96 was also evaluated. As expected, FS and S96 were significantly related to time and density. FS but not S96, were also were significantly related to treatment. FS with gypsum treatment was not different from controls and FS with table salt and benzocaine treatments were significantly reduced. The condition factor was not related to either FS or S96. FS was inversely correlated with carbon dioxide concentration. It was concluded that the additives did not improve fish transportation survival. Linear models were developed to predict the best transportation densities as a function of time

Seahorse (Hippocampus reidi) as a bioindicator of crude oil exposure

This study explored the suitability of the seahorse Hippocampus reidi (Ginsburg, 1933) for assessing biomarkers of genotoxic effects and its use as a sentinel organism to detect the effects of acute exposure to petroleum hydrocarbons. Fish were exposed to three concentrations of crude oil (10, 20 and 30. g/kg) for 96. h, and the activity of phase II biotransformation enzyme glutathione S-transferase (GST) was measured. In addition, we performed genotoxicity assays, such as comet assay, micronucleus (MN) test and nuclear abnormalities (NA) induction, on the erythrocytes of the fish species. Our results revealed that the inhibition of hepatic GST activity in H. reidi was dependent on increasing crude oil concentrations. In contrast, an increase in the damage index (DI) and MN frequency were observed with increased crude oil concentrations. These results indicate that the alkaline comet assay and micronucleus test were suitable and useful in the evaluation of the genotoxicity of crude oil, which could improve determinations of the impact of oil spills on fish populations. In addition, H. reidi is a promising "sentinel organism" to detect the genotoxic impact of petroleum hydrocarbons. © 2015

Metabolic adjustments in Satanoperca aff. jurupari (Perciformes: Cichlidae)

In this paper, we describe the enzyme levels and isozyme distribution in skeletal and heart muscle of Satanoperca aff. jurupari, (Cichlidae, subgroup Geophaginae). LDH and CS were measured in skeletal and heart muscle. Starch gel electrophoresis was used to determine the isozyme/allozyme patterns in different tissues; LDH, MDHs, PGM, PGI, ADH, G-6-PDH and SOD were screened for the numbers of loci, presence of alleles, and tissue specificity. The LDH/CS ratio in heart and skeletal muscle were 173.36 and 6.1, respectively, indicating anaerobic metabolism in the former and aerobic metabolism in the latter muscle. No inhibition by pyruvate (based on the ratios of LDH activity with 1 mM and 10 mM pyruvate) was detected in heart and skeletal muscle, indicating the presence of physiological plasticity in heart muscle. The heart can cope with anaerobic metabolism for short periods of hypoxia such as occurs in nature. Isozyme patterns for most of the enzymes analyzed were similar to the general patterns for advanced teleosts. S. aff. jurupari had no reduced LDH-B* expression in heart muscle, but the, MDHs-B* locus was duplicated, as reported for most Amazon cichlids species. Only three out of the 13 loci analyzed (PGM, PGI and SOD) were variable. These results are consistent with the metabolic profile and life style of the most cichlids. A low genetic variability may be a counterpart for plasticity, and may be guaranteed by the regulation of invariable structural genes

Lethal Temperatures for Silver Catfish, Rhamdia quelen, Fingerlings

Silver catfish, Rhamdia quelen, is widely distributed in rivers and lakes of Brazil and used in fish culture. The objective of this study was to determine the lower and the upper lethal temperatures for fingerlings of this species. Fishes were acclimated to temperatures of 16, 21, 26, and 31°C for 22 days. Experiments increasing or decreasing water temperature of the tanks were carried out to obtain 0 and 100% mortality. The mean lethal temperature (LT50) was calculated by nonlinear, sigmoid regression. The lower LT50 values were 7.71, 9.87, 10.97, and 14.22°C, and the upper values were 33.5, 33.55, 34.5, and 34.5°C for acclimation temperatures of 16, 21, 26, and 31°C, respectively. The area of the thermal tolerance polygon (expressed as °C2) for fingerlings of silver catfish was 804, indicating that this species is eurythermal. © 1999 Taylor & Francis Group, LLC

Avaliação da toxicidade do cobre para o piauçu (Leporinus macrocephalus, Garavello & Britski, 1988) por meio de parâmetros leucocitários e enzimáticos - DOI: 10.4025/actascibiolsci.v32i1.4939

Toxicity tests have been widely used as a form of monitoring degraded areas. This work has as objective to evaluate the toxicity of copper for Piauçu from the determination of LC50 for 96 hours and analysis of alterations in the enzymatic and leukocyte patterns, in sublethal exposure (25 and 50% of the lethal concentration) for 96 hours. The LC50 of copper for Piauçu, during 96 hours, is 0.09±0.03 mg L-1 Cu2+. After exposure to the sublethal concentrations, enzymatic concentrations of Alanine Aminotrasferase and Aspartate Aminotransferase did not show any significant difference between the individuals of the control and metal groups. Plasma glucose showed a significant increase in fish exposed to 25 and 50% of LC50, when compared with control. Eosinophil, lymphocyte and neutrophil showed no significant difference from the control group. Thrombocytes increased significantly in the fish exposed to 50% of the LC50, as did monocytes in fish exposed to 25 and 50% of LC50. The results indicate that Piauçu is a species sensitive to the lethal effects of copper, and that exposure to the sublethal concentrations causes immune disorder; however, it does not induce liver damage according with the measured enzymes.Como forma de monitoramento de áreas degradadas, testes de toxicidade têm sido amplamente utilizados. Este trabalho teve como objetivo avaliar a toxicidade do cobre para o piauçu a partir da determinação da CL50 96h e da análise de alterações nos padrões enzimáticos e leucocitários, em exposição subletal (25 e 50% da concentração letal) por 96h. A CL50 96h do cobre para o piauçu foi 0,09 ± 0,03 mg L-1. Após a exposição às concentrações subletal, os valores das concentrações enzimáticas de Alanina Aminotrasferase e Aspartato Aminotransferase não apresentaram diferença significativa entre os indivíduos do grupo-controle e dos expostos ao metal. A glicose plasmática apresentou aumento significativo nos peixes expostos a 25 e 50% da CL50, quando comparados ao controle. O eosinófilo, o linfócito e o neutrófilo não apresentaram diferença significativa do grupo-controle. Os trombócitos aumentaram significativamente nos peixes expostos a 50% da CL50; os monócitos, nos peixes expostos a 25 e 50% da CL50. Os resultados indicam que o piauçu é uma espécie sensível aos efeitos letais do cobre e que a exposição a concentrações subletais causa um distúrbio imunológico, porém não induz dano hepático, de acordo com as enzimas mensuradas

Acute toxicity of the water-soluble fraction of diesel in Prochilodus vimboidesKner (Characiformes: Prochilodontidae)

Diesel oil can be a source of contamination in aquatic environments, mainly as a result of spills. The effects of the water-soluble fraction of diesel (WSF) on Prochilodus vimboideswere assessed. Fish were exposed to three different WSF dilutions for up to 96 h and were compared to a control group. Damages in the fragments of DNA were analyzed using the Comet assay. The presence of erytrocyts abnormalities was assessed by micronucleus test. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activity and the accumulation of copper in gills were also analyzed. Fish exposed for 96 h had higher rates of damage than those exposed for 24 h. There was no significant difference regarding the presence of micronuclei between exposed and control fish and between 24-h and 96-h exposures. For AST, no significant difference was observed between samples collected at the two exposure times. Fish exposed to a 1:100 dilution of WSF showed higher activity of the enzyme ALT than the control fish after a 24-h exposure period. There was no bioaccumulation of copper in the gills. We conclude that the genotoxic effects of WSF in the cells are more evident in P. vimboides during an acute exposure