Tissue Clearing for the Visualization of Microplastics Ingested by Sea Urchins

Abstract

Microplastics can be ingested by a broad range of organisms. Currently, most of the methods to detect ingested microplastics are labor-intensive or results in the loss of localization information. The recent advances in tissue clearing techniques have revolutionized visualization strategies for internal structures of biological specimens. In the present study, the observation of microplastic ingestion by sea urchins led us to develop a tissue clearing protocol for the highly calcified organism to visualize internal microplastics. To clear decalcified, fragile sea urchins, we combining hydrogel-embedding of CLARITY and delipidation/RI-matching of CUBIC. This hybrid approach allowed whole-mount tissue clearing of sea urchins and ingested colored microplastics were visualized. We also tested the possible application of Nile red staining for plastics in the combination of tissue clearing. Those data suggest that tissue clearing is a promising approach not only in anatomical but also in environmental sciences.