Múltiplos biomarcadores em cascudo neotropical para avaliar a contaminação do Rio Pirapó, região norte do Paraná

Abstract

This study aimed to evaluate the contamination of the Pirapó River, northern of Paraná State, by the use of multiple biomarkers in catfish Hypostomus ancistroides. The bio-indicator was caught in three sampling points and two seasons, winter and summer. The sampling points were established along a pollution gradient: 1- Upstream: located in Apucarana city, near the headwaters of the river, the most preserved location and with good vegetation cover; 2- Intermediate: after the water treatment plant of Maringá city, with agricultural and industrial activity and scarce coverage of riparian vegetation; 3- Downstream: located after the discharge of waste from the sewage treatment plant (STP) of Maringá, with thin vegetation. The organisms collected were first anesthetized with benzocaine hydrochloride (20%), measured about length and total weight, and subsequently sectioned for removal of target tissues, which were fixed in ALFAC for 12 hours, and kept in 70% ethanol. We used the gills and livers to histopathological analysis. It’s followed routine histological procedures: dehydration, trimming, microtome and stained with H/E. The stained slides were analyzed qualitative and quantitatively in light microscopy, using Bernet index. The allometric condition factor (K) was estimated from the morphometric data of specimens associated with the slope (b) the length-weight relationship for sample point. The dependent variables were compared from two-way ANOVA followed by Tukey test, considering two factors: spatial and temporal. In general, individuals located in downstream and intermediate points had significantly higher rates of histopathological damages and smaller K values. We concluded that individuals from these points have been subjected to a higher anthropogenic stress, probably due to influence of micropollutants observed urban and industrial effluents that area.