Growth but Not Corticosterone, Oxidative Stress, or Telomere Length Is Negatively Affected by Microplastic Exposure in a Filter-Feeding Amphibian.

Microplastics (MPs) are of increasing global concern for species inhabiting aquatic habitats. However, the mechanisms behind animal responses to MPs still require comprehensive exploration. Amphibians are the most threatened vertebrate group with most species having a complex life cycle, commonly with an aquatic larval stage. Here, we investigated whether exposure to an environmentally relevant concentration of MPs affects the growth of filter-feeding larvae of the African clawed frog (Xenopus laevis), and the consequences for their stress physiology (corticosterone [CORT] levels), or health and ageing physiology (oxidative stress and telomere length, the latter in the liver and gut). We conducted a 3 × 2 experiment with three levels of fiber exposure (fibers absent -control-, and MP and cellulose fiber treatments), and two stress levels (CORT absent -control-, and CORT present simulating a stressful condition). We observed a negative impact of MP exposure on larval growth; however, this did not alter the CORT levels, oxidative stress. or telomere length. Our study shows that realistic concentrations of MPs are not enough to induce major alterations on the stress or health and ageing physiology of a filter-feeding amphibian. Whether compensatory growth responses during the post-metamorphic stages could lead to detrimental effects later in life should be explored in amphibians and other organisms with complex life cycles.