Avaliação da toxicidade de glifosato e 2,4-D em girinos de pseudis minuta e scinax squalirostris coletados em ambiente natural

Abstract

GLYPHOSATE AND 2,4-D TOXICITY EVALUATION ON PSEUDIS MINUTA AND SCINAX SQUALIROSTRIS TADPOLES COLLECTED IN NATURAL ENVIRONMENT One of the most impactful activities on the environment is agriculture which uses several toxic agents to ecosystems, polluting and poisoning native species that are not target of these substances. Therefore, assessing pesticides effects on non-target species is important for making decisions about the use, release, and mitigation of their impacts. The aim of this study was to compare and evaluate toxicity of herbicides Roundup® Original (glyphosate) and DEZ® (2,4-D) on oxidative balance and body condition parameters in Scinax squalirostris, a Brazilian native species submitted to environmentally and legally relevant concentrations in Brazil for these pesticides. Our goal was also to analyze commercial formulation of Roundup® Original impacts in oxidative balance and body condition parameters on an exclusively aquatic native species of anuran, Pseudis minuta at the larval fase. In both studies we collected animals in the same Butiazal reserve area, inside a particular property, localized in Tapes, Brazil, that cultivates rice and soybean in rotating planting. From S. squalirostris we collected 140 tadpoles from a single water body, between 25 and 34 Gosner’s stages and we kept them under controlled conditions in lab. We exposed them to three different concentrations of each of the most widely used herbicide formulations in Brazil, glyphosate and 2,4-D. In this experiment we used two control groups - acclimatization and exposure - to eliminate handling and lab time errors. From P. minuta, we collected egg masses and we kept them in controlled conditions in laboratory until tadpoles hatched and reached Gosner stage 25. Then we exposed them to 65μg/L, 250μg/L and 500μg/L of Roundup® Original. Concerning S. squalirostris, we analyzed body condition parameters such as weight, length, as well as K and Kn indexes. We also analyzed antioxidant defense enzymes (Superoxide Dismutase and Catalase), biotransformation enzyme (Glutathione Stransferase) and oxidative damage by Lipoperoxidation (TBARS) and Protein Carbonylation (PC). Whilst to P. minuta, we evaluated the same body conditions indexes, antioxidant and biotransformation enzymes, however, with regard to oxidative damage, we only evaluated Lipoperoxidation (TBARS). About S.squalirostris, an arboreal species, we observed an antioxidant defense enzymes activity modulation, especially related to glyphosate. Nevertheless, we found dose-dependent oxidative stress through protein carbonylation for 2,4-D and also in the intermediate glyphosate concentration, suggesting that 2,4-D is more toxic than glyphosate. On the other hand, we found aboveexpected growth in the lowest glyphosate concentration for P. minuta, insinuating an increase in intake and targeting nutrient for growth. Regarding the oxidative balance of P.minuta, we were not able to observe significative differences, so we raised the hypothesis of tolerance of this species, which is more anthropized than the first one and inhabits aquatic environment throughout its whole life cycle. We expect that these results ratify the value of ecotoxicological studies in native species that have different habits and that it may contribute with scientific information for decision-making about the release and use (or not) of pesticides in environment.