The gills of fish have a great external contact surface and are particularly sensitive to chemical and physical changes in the aquatic environment. The aim of this study was to examine the histopathologic alterations in the gills of Astyanax fasciatus and Cyanocharax alburnus and to determine if there is a correlation between the severity of the alterations and environmental degradation and if this biological system can be used as a tool for evaluating water quality in monitoring programmes. The gills of 107 specimens of Astyanax fasciatus and 116 of Cyanocharax alburnus were collected seasonally and processed using routine histologic techniques for fixing and embedding in paraffin and staining of sections with haematoxylin and eosin. The main alterations observed in both species were alteration of the structure of the epithelium, vacuolisation, hyperplasia of the epithelium of the primary lamella, epithelial lifting, and alteration of the structure and occurrence of aneurysms in the secondary lamella. The locations Gasometer and F. do Celupa were the ones that showed the highest frequencies of moderate and severe alterations as the highest "histopathologic alterations index" means. The most severe alterations were found to be related to the most impacted environment, indicating the presence of stressors in the water.

Histopathological alterations in liver have been widely used as a tool in studies for monitoring environmental quality.To evaluate the environmental quality in the Cachoeira river, five spots were monitored between the municipal districts of Itapé and Ilhéus, using liver histological analysis. The species chosen for analysis was Poecilia vivipara due to the fact that it is one of the most abundant in the sampling. The routine technique of inclusion and impregnation in paraffin was used, and the cuts were stained with Hematoxylin and Eosin (H & E). Histopathological alterations in the liver were evaluated semi-quantitatively and based on the severity of the lesions. The results of the histopathological alteration frequency together with the average taken from the Histopathological Alteration Index from points 1 (Vila de Itapé) and 2 (Fazenda Santa Amélia) showed that in this area the environment is more threatened because of some stressor agent, possibly contaminants that seem to be acting in the environment and endangering the health of fish. The statistic results demonstrated that there were no significant differences among points 1, 2 and 4, which means they are very similar to one another, and are ecologically endangered.Keywork: Poecilia vivipara, toxicology, histopathologic alterations. Alterações histopatológicas observadas no fígado de Poecilia vivipara(Cyprinodontiformes: Poeciliidae) como ferramenta de avaliação da qualidade ambiental do rio Cachoeira, BA ResumoAlterações histopatológicas em fígado têm sido amplamente utilizadas como ferramenta no estudo de monitoramento da qualidade ambiental. A fim de avaliar a qualidade ambiental do Rio Cachoeira, foi realizado um monitoramento em cinco pontos do rio, entre Itapé e Ilhéus, utilizando-se análise histopatológica do fígado. A espécie Poecilia vivipara foi escolhida para análise por ser uma das mais abundantes nas amostragens. Foi utilizada a técnica histológica de rotina de inclusão e impregnação em parafina, sendo os cortes corados com hematoxilina e eosina (H&E). As alterações histopatológicas no fígado foram avaliadas semiquantitativamente e baseadas na severidade das lesões. Os resultados das frequências de alterações histopatológicas juntamente com as médias de IAH dos pontos 1 (Vila de Itapé) e 2 (Fazenda Santa Amélia) demonstraram que nestas áreas os ambientes encontram-se mais comprometidos por causa da atuação de algum agentes estressores, que possivelmente, seja contaminante que deve estar atuando sobre o ambiente e comprometendo a saúde dos peixes. Os resultados dos testes estatísticos demonstraram que não houve diferença estatisticamente significativa entre os pontos Vila de Itapé, Fazenda Santa Amélia e Ponto do Pitu, e que ambos -pontos Vila de Itapé, Fazenda Santa Amélia -estão comprometidos ecologicamente, apesar de o ponto Fazenda Santa Amélia ser considerado o mais degradado de acordo com as frequências de alterações e o IAH.Palavras-chave: Poecilia vivipara, toxicologia, alterações histopatológicas.

Description of histological abnormalities in lhe bony plates of the loricariid catfish Rilleloricaria slrigi/ala (Hensel) (Teleostei, Loricariidae) and analysis of its frequeney in the lake Guaíba, Rio Grande do Sul, Bl'azil. Lirrle informarion is available abour natural populations oftishes exposed to polluted waters in Brazil. Contaminanls may be lethal or predispose jishes lo siekness, being lhe analysis ofaquatic organisms a good indicaror 01' environmental quality. The violinha, Rine/oricaria slrigi/ala (Hensel, 1868), is a common loricariid calfish in the Guaíba lake basin, Rio Grande do Sul, Brazil, and has been seleeted as a bioindieator for being resident, occwTing in more than 50% of lhe samples. and by showing externally detectable neoplasies. These are characterized by its dark pigmenlation, bony plates hypertrophy, and hypertrophy and irregular arrangemenl ofthe odonlodes. Ilislology showed hypertrophied epitelial tissues, with an increased number of secretOlY cells, blood cells, and melanina pigmenrs, giving the dark appearanee to the neoplasm. Observed JI'equeneies of neoplasm were higher in lake Guaíba lhan in eomparative samples. Inside lake Guaíba, a pattem ofdistribution ofneoplasm was observed, with rhe absence of neoplasm in tishes at the eollecred sire rhat receives warer from rio Jacuí, and frequencies of3.04 to 16.81% in the collecrion localities in ti"onr ofPorto Alegre and downstreamlocalities, that receive water from rio JacuÍ, rio dos Sinos and rio Gravataí, that drain urban and industrial area of POIio Alegre and neighborhood ciries.

The frequency of the black spot disease caused by digenetic trematodes in fish was tested as an indicator of the quality of water in the watershed of Lake Guaíba. Samples were standardised and quarterly made using a seine net at eleven sites in the basin. A total of 53,408 individuals of 66 specimens pertaining to 22 families and 8 orders were collected and analysed. The highest frequency of the disease was found in Astyanax fasciatus. The simple Chi-Squared test applied to the species showed statistically significant frequency of occurrence for three sampled sites. Two of these sites showed the highest frequencies for two consecutive sampling periods of one year and the best levels of water quality. Results of this study suggest that the association between high frequency of infestation by a parasite that causes the black spot disease in fish, and environments with less degradation in water quality, recorded from physical, chemicals and microbiological variables, could be used as an indicator of water quality in these environments.Keywords: black spot disease, environmental quality, Astyanax fasciatus, Guaíba Lake, RS, Brazil.Avaliação da qualidade ambiental através da análise da frequência da doença dos pontos pretos em assembléias de peixes, Lago Guaíba, RS, Brasil Resumo A frequência da doença dos pontos pretos, provocada por trematódeos digenéticos em peixes, foi testada como indicador da qualidade da água na bacia hidrográfica do lago Guaíba (RS). As amostragens foram padronizadas e realizadas trimestralmente com redes do tipo picaré em onze pontos desta bacia. Foram coletados e analisados 53.408 exemplares, totalizando 66 espécies pertencentes a 22 famílias e oito ordens. A maior frequência de ocorrência da doença foi verificada em Astyanax fasciatus. Um Qui-Quadrado simples aplicado para essa espécie indicou frequência estatisticamente significativa de ocorrência da doença para três locais amostrados. Dois destes locais apresentaram as maiores frequências durante dois períodos consecutivos de um ano de amostragem e os melhores níveis de qualidade de água. Os resultados deste trabalho sugerem que a associação entre a elevada frequência de infestação pelo parasito que causa a doença dos pontos pretos e os ecossistemas com menor degradação na qualidade da água, com registros de variáveis físicas, químicas e microbiológicas, pode ser utilizada como indicador de melhor qualidade ambiental.Palavras-chave: pontos pretos, qualidade ambiental, Astyanax fasciatus, lago Guaíba, RS, Brasil.

Este trabalho utiliza índices ecológicos em taxocenoses de peixes (constância de ocorrência, diversidade de espécies, riqueza, equitabilidade, índice de qualidade integrado (IQ)) como instrumento de avaliação da degradação ambiental. As amostragens foram padronizadas e realizadas sazonalmente durante dois anos, com rede de arrasto do tipo picaré, em onze pontos da bacia hidrográfica do lago Guaíba. Os pontos que apresentaram maior regularidade sazonal nos índices coincidem com locais de melhor qualidade ambiental indicados por outros fatores (frequência de anomalias, DBO5, temperatura, coliformes totais, oxigênio dissolvido). O cálculo do índice de qualidade integrado (IQ), entretanto, foi extremamente influenciado pela abundância e riqueza de espécies, sendo que os locais considerados de melhor qualidade por este índice correspondem aos de pior qualidade ambiental indicados por outros fatores. A análise realizada demonstrou que à medida que a qualidade da água melhora, o Índice de Margalef diminui. Isto demonstra que mesmo havendo uma melhora na qualidade da água, não houve uma melhora da estrutura da comunidade deste local.

A 45 day experiment was carried out to evaluate the effect of water salinity on the performance, haematological parameters and histological characteristics of the gills of the Nile tilapia, Oreochromis niloticus. The water salinity levels evaluated were: 0, 7, 14 and 21 g L-1. Nile tilapia specimens (1.62 ± 0.01 g), distributed into 20 fibreglass tanks (100 L) at a density of 15 fish per tank. There were no significant differences of the water salinity levels on daily feed intake; however, there were differences (P < 0.05) on the daily weight gain, feeding conversion rate and survival. The best results were observed for the water salinity levels of 0 and 7 g L-1. There were no differences (P > 0.05) between these levels. Regarding the haematological parameters, it was observed that the percentage of the haematocrits and the erythrocyte count were influenced (P < 0.05) by the water salinity level, which was not observed for the leukocyte count. The observed histopathological alterations were chloride cell hypertrophy, epithelial lifting, structure alteration, telangiectasia, primary lamellae cells aggregation, fusion and occurrence of aneurisms of different sizes in some secondary lamellae. Regarding the frequency of gills infection intensity, there were slight changes between the salinities of 0, 7 and 14 g L-1 and moderate changes at 21 g L-1. It is concluded that Nile tilapia can be reared in water salinities of up to 7 g L-1 without damage to the parameters evaluated in this work.

Due to the wide use of glyphosate (GLY) in soybean cultivation, their residues in the environment may affect non-target organisms such as fish, developing toxic effects. Despite GLY being widely used in Brazil, there are few studies comparing the effects of commercial formulations in native freshwater fish species. Silver catfish (Rhamdia quelen) were exposed to three different commercial formulations of GLY 48% (Orium(®), Original(®) and Biocarb(®)) at 0.0, 2.5 and 5.0 mg/L for 96 h. The effects in thiobarbituric acid-reactive substances (TBARS), catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST) and histological alterations were analysed in the liver, whereas alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were studied in the plasma. In the liver, TBARS levels increased and CAT decreased in all treatments and herbicides tested in comparison with the control group. The SOD increased at 2.5 mg/L of Orium(®), Original(®) and 5.0 mg/L Orium(®) and Biocarb(®), whereas GST increased at 2.5 mg/L Orium(®) and decreased at 2.5 mg/L Biocarb(®) when compared to the control group. The main histopathological alterations in hepatic tissue were vacuolisation, leucocyte infiltration, degeneration of cytoplasm and melanomacrophage in all GLY treatments. The ALT decreased after exposure to 2.5 mg/L of Biocarb(®) and AST increased at 2.5 mg/L of Orium(®), Original(®) and 5.0 mg/L of Biocarb(®) in comparison with the control group. In summary, the oxidative damage generated by GLY may have caused the increased formation of free radicals that led to the histological alterations observed in hepatocytes.

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