Microplastics ingestion and mouthpart morphology in common coastal marine peracarids (Arthropoda, Crustacea)

Microplastic (MP) pollution is a significant threat due to its widespread presence, hidden diffusion through ingestion by organisms, and entry into edible species. In this study, MPs were assessed in the digestive canal of peracarid crustaceans. The amphipod Gammarus insensibilis , G. subtypicus , Parhyale plumicornis , Orchestia montagui , Speziorchestia stephenseni and the isopod Ligia italica were collected in the central Mediterranean Sea and analysed to search for the relationship between mouthparts’ morphology and MPs ingestion in marine coastal environments. The specimens showed a comparable average total length (12 mm) and a similar trophic behaviour, i.e., phyto-detritophagous. The highest MP prevalence was found in the hyalid P. plumicornis (51.5% of the individuals). The second highest, the talitrid Speziorchestia stephenseni , had MPs in 40% of the individuals. In contrast, gammarid G. insensibilis and G. subtypicus had respectively 8.3% and 3.5% of the total individuals containing MPs. The results may suggest that the hyalid and the talitrid amphipod species store increased levels of MPs in coastal marine environments, as these species show morphological functional traits susceptible to ingestion of MPs, i.e. the absence of a mandibular palp, and the reduction of the maxilla-1 palp in either size and articulation.