Biomineralization biomarkers to assess microplastics toxic effects in the freshwater snail Pomacea canaliculata

Abstract

Microplastics (MPs) pollution has increased the number of reports on the toxic effects on biota, especially aquatic organisms. Recently, studies highlighted changes in ion transport and concentration, especially Ca²⁺, in organisms exposed to MPs. For calcifying organisms, such as mollusks, Ca²⁺ homeostasis is critical for their shells construction. We investigated the effects of polyethylene (PE) MPs at 20 μg/L on biomineralization biomarkers (Ca²⁺ATPase, carbonic anhydrase, hemolymph [Ca²⁺], and shell regeneration) of the freshwater gastropod Pomacea canaliculata. Two experimental sets were performed: (1) animals in physiological condition and (2) animals with their shells excised. The results of the first set showed that within 24 h, the hemolymph [Ca²⁺] decreased, and the Ca²⁺ATPase activity increased in the mantle edge. For carbonic anhydrase (CA), the activity decreased in the gland and increased in the mantle. By 72 h, the hemolymph [Ca²⁺] had not changed, whereas both enzymes had increased in both tissues. In the second set, the hemolymph [Ca²⁺] increased after 72 h, whereas Ca²⁺ATPase activity decreased in both tissues. For AC, the opposite results were observed. At 120 h, calcium pumping was still reduced and CA values increased in the digestive gland. Additionally, MPs exposure increased the capacity of the gastropods to recover their shells. Based on this, our work provides novel data associating PE microplastic exposures (at 20 μg/L) and their potential to stimulate biomineralization enzymes of P. canaliculata, as well as increase shell regeneration in excised animal; a good prerogative for further investigations on both subjects that still lacks of more robust evidence.

Keywords: Ca(2+)ATPase; Calcification; Calcium; Mollusk; Polyethylene; Shell.