Field evidence of nylon fishing-net macroplastic embedded in the tissue of a wild pearl oyster (Pinctada fucata): A histological case observation.

The objective of this study was to document and characterise an opportunistic case of macroplastic embedding within the soft tissues of a wild pearl oyster (Pinctada fucata) and to describe the associated tissue-level responses. Most existing research on plastic pollution in bivalves has focused on microplastic (<5 mm) ingestion, whereas the physical incorporation of macroplastic (>5 mm) debris into bivalve tissues remains poorly documented under field conditions. Four adult P. fucata specimens, obtained as bycatch from artisanal gill-net fishing off the southeastern coast of India (Nagapattinam, Tamil Nadu) in July 2024, were examined macroscopically and histologically. In one of the four specimens, a multifilament nylon fragment (∼2.8 cm; 0.2 g) was found deeply embedded within the visceral mass, surrounded by reactive host tissue indicative of in vivo incorporation. Polymer identity was screened with Nile Red staining and confirmed by attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). The fragment did not exhibit Nile Red fluorescence, but FTIR spectra showed diagnostic absorption bands at 3352 cm-1 (NH stretching), 1643 cm-1 (amide I), 1540-1500 cm-1 (amide II) and 1280 cm-1 (amide III) consistent with polyamide (nylon), supporting a fishing-gear origin. Hematoxylin and eosin-stained sections of tissues adjacent to the filament revealed muscle-fibre disruption, hemocyte infiltration, vacuolisation, focal necrosis and early fibrotic encapsulation, qualitatively consistent with a chronic foreign-body response. These observations are descriptive and based on a single positive case among four examined specimens, and therefore cannot be generalised to oyster populations.