Multispecies and multibiomarker assessment of fish health from Iguaçu River reservoir, Southern Brazil.

This study investigated the impact of micropollutants on fish health from Segredo hydroelectric reservoir (HRS) along the Iguaçu River, Southern Brazil, contaminated by urban, industrial, and agricultural activities. This is the first comprehensive study assessment in the river after the severe drought in the 2020s in three fish species from different trophic levels Astyanax spp. (water column depth/omnivorous), Hypostomus commersoni (demersal/herbivorous), and Pimelodus maculatus (demersal/omnivorous). Animals, water, and sediment samples were collected from three distinct sites within the reservoir: Floresta (upstream), Iratim (middle), and Station (downstream). The chemical analysis revealed elevated concentrations of metals (Al, Cu, Fe) and the metalloid As in water, or Cu, Zn, and As in sediment, surpassing Brazilian regulatory limits, while the organic pollutants as DDT, PAHs, PCBs, and PBDEs were found under the Brazilian regulatory limits. The metal bioaccumulation was higher in gills with no significant differences among sites. The species Astyanax spp. and H. commersoni displayed variations in hepatosomatic index (HSI) and P. maculatus in the condition factor index (K) between sites, while adverse effects due to micropollutants bioaccumulation were observed by biochemical, genotoxic, and histopathological biomarkers. The principal component analysis and integrated biomarker response highlighted the upstream site Floresta as particularly inhospitable for biota, with distinctions based on trophic level. Consequently, this multifaceted approach, encompassing both fish biomarkers and chemical analyses, furnishes valuable insights into the potential toxic repercussions of micropollutant exposure. These findings offer crucial data for guiding management and conservation endeavors in the Iguaçu River.

Effects of trophic 2,2', 4,4'-tetrabromodiphenyl ether (BDE-47) exposure in Oreochromis niloticus: A multiple biomarkers analysis.

Polybrominated diphenyl esters are emerging environmental contaminants with few toxicological data, being a concern for the scientific community. This study evaluated the effects of BDE-47 on the health of Oreochromis niloticus fish. The animals were exposed to three doses of BDE-47 (0, 0.253, 2.53, 25.3 ng g-1) every 10 days, for 80 days. The BDE-47 affected the hepatosomatic and gonadosomatic index in female and the condition factor by intermediate dose in both sexes. The levels of estradiol decreased and the T4 are increased, but the vitellogenin production was not modulated in male individuals. Changes in AChE, GST, LPO and histopathology were observed while the integrated biomarker response index suggests that the lowest dose of BDE-47 compromised the activity of antioxidant enzymes. The oral exposure to BDE-47 in environmental concentrations is toxic to O. niloticus and the use of multiple biomarkers is an attribution in ecotoxicology studies and biomonitoring programs.

Exposure to pollutants present in Iguaçu River Southern Brazil affect the health of Oreochromis niloticus (Linnaeus, 1758): Assessment histological, genotoxic and biochemical.

Urban sewage is a source of major contamination in aquatic systems and contributes to environmental and human health disturbances. This study investigates the effects of sewage-polluted waters from Iguaçu River on the health of juvenile Oreochromis niloticus. Two hundred four specimens were exposed to riverine water in four groups: no diluted, 25 and 50 % diluted water and a control group without tested water for 72 days. Biological samples were obtained for histopathological, neurotoxicity, antioxidant defenses, genotoxicity, metallothionines expression and polycyclic aromatic hydrocarbons (PAHs) metabolites. The results showed histopathological alterations in liver and gills, genotoxic alteration in erythrocytes, reduction of acetylcholinesterase activity in brain and muscle, activation of antioxidant defenses in the liver, recruitment of metals by metallothionein and the detection of PAHs metabolites in bile. These results demonstrate that juveniles of O. niloticus are susceptible to Iguaçu River exposure water and they can be used as indicator of water quality.

Avaliação dos efeitos tóxicos do metilmercúrio na retina de duas espécies de teleósteos: Hoplias malabaricus e Danio rerio, utilizando um conjunto de biomarcadores biológicos

Em exposições especificamente relacionadas ao metilmercúrio (MeHg), o principal órgão alvo é o Sistema Nervoso Central (SNC). Os efeitos morfológicos do metilmercúrio nos fotorreceptores da retina de Hoplias malabaricus, traíra, foram investigados através de técnicas histopatológicas. Os exemplares de traíra foram distribuídos em três grupos: um grupo controle e dois grupos expostos ao MeHg. A contaminação trófica e subcrônica foi realizada através de exemplares vivos de Astyanax sp os quais receberam intraperitonealmente um volume de solução aquosa de MeHg correspondente a (0,075µg/g de traíra) ou (0,75µg/g de traíra). Quinze peixes por condição experimental foram sacrificados após 70 dias de exposição e os olhos foram coletados para as análises de microscopia de luz, microscopia eletrônica de transmissão e microscopia eletrônica de varredura. Através de análises químicas quantificamos o mercúrio em músculo e observamos em ambas as doses um acúmulo do metal. Para a maior dose do metal (0,75µg/g), as análises histopatológicas revelaram alterações nas membranas que unem os dois elementos de um cone pareado, degeneração da camada dos fotorreceptores e alterações morfológicas no segmento interno e segmento externo dos bastonetes. As análises também demonstraram alterações estruturais na membrana plasmática do segmento externo e alterações no processo de eliminação dos discos membranosos dos fotorreceptores. (...)

... No momento da eliminação dos discos antigos foi observada a formação de vacúolos e também uma anormal eliminação dos discos membranosos pelas partes laterais do segmento externo. Para a menor dose do metal (0,075µg/g) além da alteração observada nas membranas que unem os cones pareados e da degeneração celular na camada dos fotorreceptores, observamos uma descontinuidade estrutural dos discos membranosos do segmento externo dos fotorreceptores. Todas estas alterações histopatológicas nos levam a concluir que o metilmercúrio induz alterações histopatológicas nas células da camada dos fotorreceptores podendo consequentemente trazer danos fisiológicos para toda a retina

In exposures specifically related to methylmercury (MeHg), the main target organ is the Central Nervous System (CNS). In this study, morphological effects of methylmercury in retinal photoreceptors of Hoplias malabaricus, trahira, through histopathological techniques were investigated. Some mature fish were divided in three groups - one control group and the other two which were exposed to MeHg. The trophic and subchronic contamination was performed by live specimen of Astyanax sp which received a volume of aqueous solution of MeHg corresponding to (0,075µg /g trahira) or (0,75µg /g trahira). In an experimental condition, fifteen fish were sacrificed after 70 days of exposure and their eyes were collected for analysis of light microscopy, electron transmission microscopy and scanning electron microscopy. Through chemical analysis the amount of mercury found in muscle was quantified. In both doses an accumulation of the metal in the muscle of these animals was observed. For the highest dose of metal (0,75µg /g), the histopathological analysis revealed changes in the membrane that connects the two elements of a paired cone, cellular degeneration in the layer of photoreceptors and morphological changes in the internal and outer rod segments. (...)

... The analysis also showed structural changes in the plasma membrane of the outer segment and changes in the process of removal of membranous discs in the apical region of a photoreceptor. At the time of disposal of old discs, the formation of vacuoles and also an abnormal membranous discs removal through the sides of the outer segment were observed. For the smallest dose of the metal (0,075µg/g) besides the morphological changes observed in the membrane which unites the paired cones and cellular degeneration throughout the layer of photoreceptors, a structural discontinuity of the membranous discs of the outer segment were observed in radial sections of rods. All these histopathological changes lead us to conclude that methylmercury induces morphological changes in cells of the layer of photoreceptors, and therefore causing physiological damage to the smooth functioning of the retina