Relationship between metal contamination and altered morphology of the carapace and chelipeds of the crab Neohelice granulata in the Bahía Blanca estuary (Argentina)

Abstract

The accumulation of metals in estuarine environments represents potential threats to both aquatic ecosystems and human health, highlighting the need for reliable in situ biomarkers of contamination. In the burrowing crab Neohelice granulata (Brachyura, Varunidae), previous studies have shown that biochemical markers may be influenced by seasonal fluctua-tions, limiting their usefulness for assessing spatial patterns of metal exposure. Recently, morphological variation among organisms has been proposed as a biomarker of environmental stress. Building on this framework, the present study aimed to evaluate whether metal contamination is associated with morphological changes in N. granulata populations from different sites of the Bahía Blanca estuary, Argentina. Concentrations of Cd, Cr, Cu, Fe, Pb, and Zn were measured in sediments and crab hepatopancreas, and their relationship with carapace and chelipeds morphology were analyzed by traditional and geometric morphometric approaches. Results revealed similar spatial patterns of metal loads in sediments and crab hepatopancreas, reflecting differences in anthropogenic impacts among sites. Moreover, significant morphological differences in carapaces were detected among crab populations, consistent with the observed gradient of metal contamina-tion. These findings suggest that metal exposure may be associated with the morphological variation in N. granulata and highlight its potential use as a biomarker of environmental stress in estuarine crabs. Finally, geometric morphometrics of the carapace proved more effective than traditional chelipeds morphometrics in distinguishing crabs’ populations exposed to different levels of metal contamination.