Polystyrene microplastics did not affect body growth and swimming activity in Xenopus laevis tadpoles

A growing number of studies have highlighted the contamination and the effects towards organisms of diverse microplastics (μPs) in the marine environment. Surprisingly, although the main sources of μPs for marine environments are inland surface waters, the information on the occurrence and the effects of μPs in freshwater ecosystems is still scant. Thus, the aim of the present work is to investigate the ingestion and possible adverse effects due to the exposure to polystyrene μPs (PSμPs; Ø = 3 μm) on tadpoles of the Amphibian Xenopus laevis. Larvae at the developmental stage 36, prior to mouth opening, were exposed under semi-static conditions to 0.125, 1.25, and 12.5 μg mL^-1 of PSμPs, and allowed to develop until stage 46. At the end of the exposure, the digestive tract and the gills from exposed and control tadpoles were microscopically examined, as well as changes in body growth and swimming activity. PSμPs were observed in tadpoles' digestive tract, but not in the gills, from each tested concentration. However, neither body growth nor swimming activity were affected by PSμPs exposure. Our results demonstrated that PSμPs can be ingested by tadpoles, but they did not alter X. laevis development and swimming behavior at least during early-life stages, also at high, unrealistic concentrations.