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Comparative study of the toxic effects of polystyrene microplastic particles of different sizes on the livers of pearl gentian grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂)
Original title: Comparative study of the toxic effects of polystyrene microplastic particles of different sizes on the livers of pearl gentian grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂)
Summary
Scientists found that tiny microplastic particles (smaller than the width of a human hair) can pass through fish intestines into their bloodstream and pile up in the liver, causing inflammation, fat buildup, and lasting organ damage—while larger plastic bits mostly just clog the gut and blood vessels with less severe harm. Since these grouper are a popular seafood fish, this suggests the smallest, often invisible plastic particles in our oceans may pose the greatest health risks to marine life—and raises questions about what that could mean for the fish we eat.
Marine microplastic (MP) pollution and its ecotoxicological effects represent a core focus in global marine environmental research. To assess the toxic effects and mechanisms of different-sized PS-MPs, pearl gentian grouper were exposed to suspensions of two particle sizes (5 μm and 180-220 μm) at a concentration of 500 μg/L for 3, 7, or 14 days. The results revealed a significant size-dependent pattern of the toxic effects: both particle sizes reduced the hepatosomatic index (HSI) but did not affect survival rates. Small (5 μm) MPs penetrated the intestines, entered the circulatory system, accumulated in the liver, and induced progressive liver damage (hepatocyte vacuolation, lipid deposition, and inflammatory infiltration), leading to the collapse of the antioxidant system; moreover, early exposure upregulates the proinflammatory factors IL-1β, IL-8, and TNF-α, quickly triggering an acute inflammatory response and promoting fatty acid oxidation while inhibiting fat synthesis, resulting in energy metabolism imbalance. In contrast, large MPs (180-220 μm) remained mainly in the intestinal tract and caused local inflammation. Liver blood cell infiltration was caused by the obstruction of microvessels by MPs, resulting in circulatory disorders, which are associated mainly with acute oxidative stress. This blockage demonstrated a distinct delayed regulatory mechanism for immune interference, directly and persistently impeding lipid metabolism and inhibiting the expression of PPAR-α and PPAR-γ. In conclusion, compared with large MPs, small MPs pose more severe comprehensive health risks to pearl gentian grouper because of their ability to cross barriers, their accumulation capacity, and the various toxic effects that cause harm over time.