LETÍCIA MENEZES FREITAS

AUTHOR: LETÍCIA MENEZES FREITAS

TITLE: BRAIN MORPHOLOGY AND EMBRYONIC NEUROTOXICOLOGY OF 2,4-D IN Tropidurus torquatus (SQUAMATA: TROPIDURIDAE)

ADVISOR: MÔNICA RODRIGUES FERREIRA MACHADO

DEFENSE DATE: 02/28/2020

ABSTRACT

Pesticides have been used since antiquity, nevertheless synthetic products emerged only last century and currently Brazil is the biggest consumer of these substances. 2,4- D is a selective herbicide for broad-leaved weeds, used in several types of crops. Usually 2,4-D is eliminated in urine in animals, but when the renal clearance rate is exceeded, adverse effects, including neurotoxic ones, appear. Few studies evaluate the effect of 2,4-D on embryonic development, which is necessary because young organisms are more sensitive than adults. With this in mind we aim to evaluate the effect of 2,4-D DMA® 806 BR on the embryonic development of the brain of Tropidurus torquatus. We also aimed to describe the brain of Tropidurus torquatus as the basis for the toxicological study. This species is abundant and by inhabiting crops it can naturally contaminate itself with pesticides, making it a good animal model. Adult animals were captured and euthanized for the macro- and microscopic description of the brain. Pregnant females were collected and kept in terrariums until oviposition. Eggs were randomly distributed into two groups, control and 2,4-D. The substrate of the 2,4-D group was contaminated shortly after oviposition with a dose corresponding to 1.5L/ha, and the control’s substrate was watered with the same quantity of water. Embryos were collected on days 15, 30 and 60 after oviposition. The embryos' brains were submitted to paraffin inclusion for H.E. staining and the volume of the optical tectum was estimated using stereology to compare both groups. A decrease in volume was observed in the 2,4-D group on day 15, but no differences were found on day 30, suggesting that 2,4-D has a mild neurotoxic effect at the recommended dose, which may be reversible.