Embryotoxic Effects of Monosodium Methyl Arsenate ( MSMA ) on Gallus gallus : Morphological and Morphometric Evidence of Developmental Disruptions

Abstract

Anthropogenic activities and the large volume of compounds released into the environment are sources of contamination for plants, animals, and humans. The herbicide monosodium methyl arsenate (MSMA) ranks among the best‐selling agricultural pesticides in Brazil. It is classified as highly toxic, containing arsenic, which crosses the placenta, reaching the developing embryo. To assess the toxic effects of these chemicals, model organisms such as chicken embryos are used, as they share phylotypic features with human embryos in the early stages of development, allowing extrapolation between species. This study aimed to identify developmental alterations in chicken embryos induced by MSMA exposure after 3 and 7 days of incubation. The experiment involved three groups of fertilized eggs injected with 0.079, 0.79, and 7.9 μg mL −1 of an MSMA solution, along with two control groups. We collected embryos to assess mortality rates, morphometric measurements, and morphological alterations. MSMA exposure was associated with embryo mortality, with a statistically significant increase in mortality observed in the MSMA II group after 7 days of incubation, and a non‐significant tendency toward higher mortality in the remaining treated groups at the same period. Seven‐day embryos exposed to MSMA exhibited significant reductions in embryo area and head, limb, and trunk length. Furthermore, MSMA exposure led to malformations in the cephalic region, neural tube, heart, optic vesicle, limbs, and beak, along with abnormal body curvature and body wall. These anomalies correspond to congenital disorders reported in humans, such as anencephaly, myelomeningocele, and skeletal malformations. These outcomes reveal the harmful effects of MSMA on chicken embryo development and suggest potential risks for human embryogenesis.