Microplastics influence physiological processes, growth and reproduction in the Manila clam, Ruditapes philippinarum

Microplastics (<5 mm) are widely distributed in marine environments and pose a serious threat to bivalves. Here, the ingestion and accumulation of polystyrene microplastics (PS microplastics, diameters 5 and 10 μm) by the Manila clam, Ruditapes philippinarum, and their impacts on physiological processes, growth and reproduction were studied. The results showed that both PS microplastics were ingested by the Manila clam and accumulated in their gills, hepatopancreases and intestines. Furthermore, the accumulation of 5 and 10 μm PS microplastics significantly increased the rates of respiration and excretion while significantly decreasing feeding and absorption efficiency (AE), leading to a dramatically reduced amount of energy available for growth (SfG) and ultimately led to slower growth. The dynamic energy budget (DEB) model predicts that PS microplastic exposure for 200 days would cause lower shell/flesh growth rates and reproductive potentiality. Transcriptomic profiles support these results, as carbon and protein metabolism and oxytocin and insulin-related signaling pathways were significantly altered in clams in response to PS microplastics. This study provides evidence that microplastics strongly affect the physiological activities, energy allocation, growth and reproduction of filter-feeding bivalves.