Efeito do herbicida Ácido 2,4-diclorofenoxiacético (2,4-D) no desenvolvimento embrionário e larval do microcrustáceo Artemia franciscana e do equinodermo Mellita quinquiesperforata

Abstract

A great increase in population was observed during the twentieth century. This fact required a higher agricultural productivity, which has leaded to an indiscriminate use of pesticides. These compounds might reach different ecosystems, from terrestrial to aquatic ones. For this reason, they can potentially damage the environment and non-target organisms. Herbicides are the most used class of pesticides, especially 2,4-dichlorophenoxyacetic acid (2,4-D), second most commercialized herbicide in Brazil. Hence, the present work aimed to evaluate the effects of the herbicide 2,4-D on the larval development and morphology of the microcrustacean Artemia franciscana and on the fertilization and embryonic and larval development of the sand dollar Mellita quinquiesperforata. We exposed A. franciscana larvae to different pure 2,4-D concentration (≥98% purity ; 50 to 500 mg.L -1 ) and larvae mobility and morphology was analyzed under light microscopy after 24 h or 48 h. Gametes, zygotes, and larvae of M. quinquiespeforata were exposed to 2,4-D (50 to 500 mg.L -1 ) and the fertilization and embryonic (4-cell stage and gastrula) and larval (48 hpf) development monitored under light microscopy. The four highest 2,4-D concentrations (200, 300, 40, and 500 mg.L -1 ) reduced the mobility rate of A. franciscana larvae during both exposure times. The EC50 value was 365.1 mg.L -1 (24 h). In addition, the herbicide negatively affected larvae morphology. The two highest 2,4-D concentrations (400 and 500 mg.L -1 ) blocked M. quinquiesperforata fertilization and embryonic development. In addition, 2,4-D (300 and 400 mg.L -1 ) disturbed echinoid larval development. The present work shows that only 2,4-D concentrations much higher than those found in aquatic environments (4 to 30 µg.L -1 ) affected A. franciscana larvae physiology and the fertilization and embryonic and larval development of M. quinquiesperforata. Further studies to evaluate the lethal and sublethal effects of exposure to the herbicide and its different formulations, alone and in mixtures with other environmental contaminan ts, in non-target organisms, may contribute to a better understanding of the toxicological profile of the herbicide.