Histopathological analysis of liver of the catfish Pimelodus maculatus in a tropical eutrophic reservoir from Southeastern Brazil

We described liver tissues of the long-whiskered catfish Pimelodus maculatus using histological techniques through structures stained with hematoxylin and eosin. A total of 21 adult individuals were collected using gill nets during the winter of 2012, in a eutrophic reservoir in Southeastern Brazil. The main aim was to characterize the tissues and eventual changes, since this organ has a notable sensitivity to changes in altered aquatic systems. The liver contains the exocrine pancreas (hepatopancreas) that have pancreatic cells arranged around a branch of the portal vein. The hepatocytes are diffuse and arranged in cords. Normal liver of P. maculatus have a continuous compact field of weakly eosinophilic, rounded hepatocytes with scattered islands of connective tissue that enclose the bile ducts and blood vessels. The organization of exocrine pancreatic tissues is similar to the acinar morphology of many teleosts. Histopathological alterations in liver were evaluated semi-quantitatively and based on the severity of the lesions. The alterations in each organ were classified in progressive stages of damage to the tissue. Six types of liver alterations were found: 1) cytoplasmic vacuolization; 2) congestion; 3) inflammatory infiltrated; 4) infiltration of adipocytes; 5) steatosis; 6) granuloma. Incidence of melanomacrophage centers were observed in the liver. However, we cannot directly associate such changes with the eutrophic conditions of the reservoir, because we have no available reference area to compare. These findings are a baseline contribution, which enables comparisons with similar fish species in other tropical aquatic systems in further studies.

Induced CYP1A activity and DNA damage in fish from the middle Paraíba do Sul River basin, southeastern Brazil / Atividade induzida de CYP1A e danos de DNA em peixes do trecho médio da bacia do rio Paraíba do Sul, sudeste do Brasil

The Paraíba do Sul River (PSR) drainage basin in Southeastern Brazil covers one of the most industrialized and densely populated regions of the country. The impact of chemical contamination on the PSR basin seems to be more pronounced in its middle reach where a number of potentially polluting plants are located. In this study, we used hepatic EROD activity - a biomarker of exposure to CYP1A-inducing pollutants (e.g. PAHs, PCDD/Fs, PCBs) - and the incidence of micronucleated erythrocytes (Mn) in the peripheral blood - a biomarker of effects of DNA-damaging agents (e.g. PAHs) - to evaluate the effects of pollution on two native fish species, Geophagus brasiliensis and Pimelodus maculatus. Results showed that the incidence of Mn and EROD in G. brasiliensis and P. maculatus from the two most downstream sites (Três Rios Town and Piabanha River) were markedly higher than the incidence of Mn and EROD recorded in fish from the most upstream site (Funil Reservoir). Our findings are consistent with the view that CYP1A-inducing activity and increased DNA-damage are found in fish caught in sampling sites located downstream of the stretch where there are several industries that are potential sources of PAHs and CYP1A-inducing contaminants.

O rio Paraíba do Sul (RPS) drena uma das mais industrializadas e densamente povoadas áreas do sudeste do Brasil. O impacto de contaminação química no RPS parece ser mais pronunciado no segmento médio da bacia onde se localiza grande número de indústrias potencialmente poluidoras. Neste estudo, foi avaliada a atividade hepática EROD – um biomarcador de exposição a poluente indutores da CYP1A (e.g. HAPs, PCDD/Fs, PCBs) – e a incidência de eritrócitos micronucleados (Mn) no sangue periférico – um biomarcador de efeitos de agentes de danificação do DNA- (e.g. HAPs) – para avaliar o efeito de poluição sobre dois peixes nativos, Geophagus brasiliensis e Pimelodus maculatus. Os resultados apresentaram que a incidência de Mn e EROD em G. brasiliensis e P. maculatus nos dois locais no trecho mais baixo (Três Rios e rio Piabanha) foi marcadamente mais elevada do que a incidência e a atividade EROD registradas em peixes dos locais mais à montante (reservatório do Funil). Estes resultados são consistentes com a visão de que atividade indutora de CYP1A e elevadora de danos no DNA são encontradas em peixes capturados em locais abaixo do trecho onde grande número de indústrias são potenciais fontes de poluição de indutores de contaminantes HAPs e CYP1A.

The use of biomarkers for assessing effects of pollutant stress on fish species from a tropical river in Southeastern Brazil / O uso de biomarcadores para avaliar efeitos de estresses de poluentes sobre espécies de peixes em um rio tropical no sudeste do Brasil

Biomarkers are measurements within an organism that respond to environmental effects and are used as tools in bioassessment programs since they reflect physiological changes induced by exposure to pollutants. The hepatosomatic index (HSI) and the condition factor (CF) in three fish species Geophagus brasiliensis, Hypostomus affinis and Hypostomus auroguttatus were used to assess effects of pollutant stress in a tropical river during two seasons (dry and wet). Fish from the least disturbed sites had the lowest condition factor (CF) and the lowest HSI, whereas those from sites near pollutant discharges had the highest CF and HSI. Higher HSI and lower CF occurred during the dry season. It is suggested that species adapted to stressful conditions take advantage on food availability from organic loads or unoccupied niches by lesser tolerant species, increasing CF. We concluded that higher HSI values were directly associated with environmental stress whereas the higher CF values are related to availability of food resources derived from organic loads or other sources. CF and HSI are simple and cost-effective, thus suitable as routine screening tools in pollution monitoring, but caution should be taken in relating changes in physiological measurements and any specific pollutant to prevent misinterpretation.

Biomarcadores são medidas dentro de um organismo que respondem a efeitos ambientais e são utilizadas em programas de bioavaliação, já que refletem alterações fisiológicas induzidas pela exposição a poluentes. O índice hepatossomático (IHS) e o fator de condição (FC) das espécies Geophagus brasiliensis, Hypostomus affinis e Hypostomus auroguttatus foram calculados em um rio tropical durante duas estações (seca e cheia). Peixes de locais menos alterados apresentaram menores FC e IHS, enquanto os de locais próximos de descargas de poluentes apresentaram maiores FC e IHS. Maiores IHS e menores FC ocorreram durante a estação seca, comparados com a estação chuvosa. É sugerido que espécies adaptadas às condições estressantes levam vantagem da disponibilidade de alimentos próxima às descargas orgânicas ou nichos não ocupados por espécies menos tolerantes, aumentado o FC. Os valores mais elevados do IHS foram diretamente associados ao estresse ambiental, enquanto os valores mais elevados FC estão relacionados com a disponibilidade de recursos alimentares derivados de descargas orgânicas ou outras fontes. FC e IHS são simples e de baixo custo, portanto, adequados como ferramentas no controle da poluição, mas cuidados devem ser tomados ao relacionar suas mudanças às medições fisiológicas ou a qualquer poluente específico para evitar efeitos de interferência.