RESUMO
Nanotechnology has been used to apply nanoparticle essential elements to enhance the ability of animals to absorb these elements and consequently improve their reproductive performance. High concentrations of nanoparticles (NPs) can directly harm a range of aquatic life forms, ultimately contributing to a decline in biodiversity. Helisoma duryi snails are a good model for studying the toxicological effects of bulk zinc oxide (ZnO-BPs) and nano zinc oxide (ZnO-NPs) on freshwater gastropods. This study aimed to compare the toxic effects of ZnO-BPs and ZnO-NPs on H. duryi snails and explore how waterborne and dietary exposure influenced the reproductive performance of this snail. ZnO-BPs and ZnO-NPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray powder (XRD). This study revealed that the size of ZnO-BPs and ZnO-NPs were 154 nm and 11-31 nm, respectively. The results showed that exposure of adult snails to sub-lethal concentrations of both ZnO forms (bulk and nano) for 24 h/week for 4 weeks markedly changed their reproductive performance in a concentration-dependent manner, where fecundity was negatively affected by high concentrations. It was concluded that dietary exposure to the lowest tested concentration of ZnO-NPs (1 ppm) has a positive effect as the number of eggs and egg masses/snails increased and the incubation period decreased. Also, poly-vitelline eggs (The formation of twins) were observed. ZnO-NPs at low concentrations positively affect the reproductive performance of snails, especially after dietary exposure. The results revealed that 1 ppm ZnO-NPs could be supplementary provided to snails to improve their fertility, reduce the developmental time course, increase hatchability percentage, and produce poly-vitelline eggs.