Embryotoxicity of nitrophenols to the early life stages of zebrafish (Danio rerio).

The nitrophenols (NPs) are water-soluble compounds. These compounds pose a significant health threat since they are priority environmental pollutants. In this study, 2-Nitrophenol (2NP) and 2,4-dinitrophenol (DNP) were examined for embryo and early life stage toxicity in zebrafish (Danio rerio). Acute toxicity and teratogenicity of 2NP and DNP were tested for 4 days using zebrafish embryos. The typical lesions observed were no somite formation, incomplete eye and head development, tail curvature, weak pigmentation (≤48 hours postfertilization (hpf)), kyphosis, scoliosis, yolk sac deformity, and nonpigmentation (72 hpf). Also, embryo and larval mortality increased and hatching success decreased. The severity of abnormalities and mortalities were concentration- and compound-dependent. Of the compounds tested, 2,4-DNP was found to be highly toxic to the fish embryos following exposure. The median lethal concentrations and median effective concentrations for 2NP are 18.7 mg/L and 7.9 mg/L, respectively; the corresponding values for DNP are 9.65 mg/L and 3.05 mg/L for 48 h. The chorda deformity was the most sensitive endpoint measured. It is suggested that the embryotoxicity may be mediated by an oxidative phosphorylation uncoupling mechanism. This article is the first to describe the teratogenicity and embryotoxicity of two NPs to the early life stages of zebrafish.

The extramacrochaetae gene is required for blastokinesis in silkworm, Bombyx mori.

In silkworm, Bombyx mori Linnaeus (Lepidoptera: Bombycidae), blastokinesis results in embryo reversal from ventrally to dorsally convex flexion. In this study, we showed that the extramacrochaetae (emc) gene is required for blastokinesis in silkworm. Depletion of Bmemc expression via RNA interference led to severe phenotypic defects in blastokinesis. The defective embryos failed to invert their body sides during blastokinesis. This caused the posterior half of the abdomen to abnormally fold back toward the dorsal side, forming a U-shaped morphology. Dorsal closure was also disrupted. Our results suggest that Bmemc is involved in blastokinesis of silkworm embryos. J. Exp. Zool. (Mol. Dev. Evol.) 324B: 405-409, 2015. © 2015 Wiley Periodicals, Inc.

Paraquat-induced oxidative stress response during amphibian early embryonic development.

In addition to the endogenous production of reactive oxygen species (ROS) as a result of normal development, amphibian external development often forces embryos to deal with oxidative stress-producing agents present in the environment. Embryos should therefore develop protective systems to reduce ROS toxicity and achieve successful development. The present work was aimed to characterize the effects produced by the widespread-used ROS-generator pesticide Paraquat during early embryonic development in the toad Chaunus arenarum, as well as to get insights into the defense response elicited by amphibian embryos. The approach consisted in generating a sharp and brief oxidative stress condition early during embryonic development to stimulate the cellular mechanisms involved in ROS-antioxidant response. Results revealed that Paraquat-treatment reduced the ability of embryos to develop normally, leading to arrests of development and severe malformations such as tail abnormalities, abdominal edema, reduced head development and curved dorsal structures. Although Paraquat effects were morphologically evident from gastrula stage on, alterations such as chromatin condensation were observed even at blastula stage by histological examinations. Regarding detoxifying enzymes, a significant induction of Mn-superoxide dismutase activity was detected at stages beyond gastrula in embryos surviving Paraquat treatment, suggesting a major role of this enzyme in the antioxidant response during early embryonic development.