Effects of Metallic Nanoparticles Treatments on the Development of the Pool Frog, <i>Pelophylax lessonae</i> (Amphibia: Ranidae)

The effects of treatments of pool frog embryos of Pelophylax lessonae with engineered zerovalent nanoparticles of Fe Co, and Ni at increasing concentrations (½ LC₅₀, LC₅₀, and 2 × LC₅₀) were studied at macroscopical and microscopical levels, focusing on the epidermis that is often subject to physiological changes in response to environmental factors. Total body length and eye diameter were statistically higher in the control groups. A significantly higher percentage of embryos in the controls reached later Gosner developmental stages (19-23) than the treatments. Malformations such as ventral blister, microcephalia, bent body axis, and microphthalmia were significantly more frequent in the Co and Ni treatments than in the controls. In treated epidermis, ciliated, goblet, and small secretory cells resulted in a significantly larger volume than the same cell types in control embryos. At the ultrastructural level, ciliated cells showed stuck cilia and mitochondrial swelling, as well as cytoplasmic inclusions. Small secretory cells exhibited a significantly higher number of secreting vacuoles, suggesting an increased secretion. In conclusion, nanoparticles affect the development of frog embryos in multiple ways, even if the mechanisms are still mostly unknown.