Segmentation of Renal Thyroid Follicle Colloid in Common Carp: Insights into Perfluorooctanoic Acid-Induced Morphometric Alterations.

Perfluorooctanoic acid (PFOA) is a globally prevalent contaminant of concern recognised for its persistence and detrimental effects on both wildlife and humans. While PFOA has been established as a disruptor of thyroid function, limited data exist regarding its impact on thyroid morphology. The kidney of the common carp ( Cyprinus carpio ) harbours numerous thyroid follicles, rendering it a valuable biomarker organ for investigating PFOA-induced thyroid alterations. Renal tissue slides, stained with the Alcian blue/PAS method, were examined from carp in three experimental groups: unexposed, exposed to 200 ng L -1 , and exposed to 2 mg L -1 of PFOA over 56 days. Thyroid follicle colloids were segmented, and related morphometric parameters, including perimeter, area, and shape descriptors, were obtained. Statistical analyses revealed significant reductions in thyroid follicle colloid perimeter and area in the 200 ng L -1 PFOA group compared to the unexposed and 2 mg L -1 PFOA groups. Additionally, the fish exposed to PFOA exhibited a significantly higher follicle count compared to the unexposed fish. These findings collectively suggest that PFOA induces thyroid folliculogenesis, emphasising its impact on thyroid morphology even at an environmentally relevant concentration (200 ng L -1 ).