Efeito do herbicida diuron no desenvolvimento do microcrustáceo Artemia franciscana e do equinodermo Mellita quinquiesperforata

Abstract

Brazil has led the ranking as the largest consumer of pesticides in the world for 15 years. Among the most used classes of pesticides are herbicides, such as diuron, widely used in sugarcane crops in the country. These compounds are applied to crops and pose a potential risk when reaching aquatic ecosystems. Therefore, the present work aimed to evaluate the effects of the herbicide diuron on the mobility, morphology, cell death and response to oxidative and metabolic stress of larvae of the microcrustacean Artemia franciscana, and on fertilization and embryonic and larval development of the echinoderm Mellita quinquiesperforata. We exposed A. franciscana larvae to different concentrations of diuron at its highest purity (≥98%; 0.01 to 30 mg.L-1 ) and nauplii mobility, morphology and cell death were analyzed after 24 h or 48 h under light microscopy. The evaluation of the response to oxidative and metabolic stress took place after the same exposure time based on the activity of the enzymes CAT, GPX, GST and LDH. Gametes, zygotes and larvae of M. quinquiesperforata were exposed to different concentrations of the herbicide (1 to 100 mg.L-1) and fertilization, embryonic development (stages: second cleavage, 90 mpf; and gastrulation, 13 hpf) and larval (48 hpf) were monitored under light microscopy. The herbicide was able to negatively affect the mobility of A. franciscana larvae from 10 mg.L-1 (24h-EC50: 13.6 mg.L-1 ; 48h-EC50: 8.89 mg.L-1 ), and the increase in the pattern of apoptotic cells showed agreement with these results. Its morphological development was affected from the lowest tested concentration (5 mg.L-1 ; CENO). The activity of tested enzymes was also altered at the lowest concentration tested (0.01 mg.L-1 ). Fertilization of M. quinquiesperforata was affected from 50 mg.L-1 (pre-exposure to eggs), while the lowest concentration that affected the development of this echinoderm was 15 mg.L-1 (larval development; 24h-EC50: 11.19 mg.L-1 ). This study showed greater resistance of both species tested when compared to the sensitivity presented by other aquatic invertebrates. Furthermore, environmentally relevant concentrations were toxic to A. franciscana. Complementary studies that investigate the effects of diuron over a longer exposure time and more sensitive parameters can provide greater understanding of the ecotoxicological risks of this compound.