This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In a paper published in the journal Marine Pollution Bulletin, researchers at Kyushu University report on what happens when wharf roaches, a common shoreline scavenger, eat expanded polystyrene (EPS). Roaches that fed on EPS showed no significant reduction in lifespan, but their guts displayed altered expression of genes involved in chemical defense, DNA repair and digestion.
Analysis of the wharf roach gut microbiome showed little change, but several rare microbes were found only in the EPS-fed specimens. In coastal areas, EPS—commonly referred to as Styrofoam—is one of the major components of marine plastic pollution. It is prevalent because its low density and high buoyancy allow it to drift over long distances and accumulate on beaches.
Wharf roaches (Ligia spp.) are common coastal isopods that act as scavengers, consuming organic matter and contributing to nutrient cycling in shoreline ecosystems. They have also been found to consume plastic pollution that washes up on shore. This makes wharf roaches useful models for investigating the biological effects of EPS ingestion and a potential sentinel species for coastal plastic pollution.
A research team led by Professor Emeritus Yuji Oshima at Kyushu University's Faculty of Agriculture conducted a laboratory exposure experiment to investigate the effects of EPS ingestion in wharf roaches. The researchers compared EPS-fed wharf roaches with a starved control group and used multi-omics approaches to analyze gene expression in the gut and the composition of the gut microbiome. "Our earlier fieldwork showed that wharf roaches chew EPS and excrete it as much smaller fragments, suggesting that these animals can help turn large pieces of foam into microplastics.
However, the biological effects of ingesting EPS in the animals themselves remain unknown," says Oshima. "We wanted to find out whether swallowing foam comes at a biological cost for these shoreline scavengers." The researchers first examined whether EPS ingestion affected the lifespan of wharf roaches. Field-collected wharf roaches were divided into two groups: One group was given only pieces of a commercially available polystyrene foam board for one week, while the control group was given no food.
EPS exposure did not significantly affect survival. Foam-fed wharf roaches lived for an average of 27.8 days, compared with 31.6 days for the unfed controls. However, this 3.8-day difference was not statistically significant, suggesting that EPS ingestion did not measurably reduce lifespan under the experimental conditions.
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