Histopathological assessment in gills and digestive gland to evaluate the health status of Mytilus platensis (Bivalvia, Mytilidae) from a seaport area of North Patagonia Argentina.

LEIS, MAGALÍ; NOYA ABAD, TATIANA; LO NOSTRO, FABIANA; KNACK DE ALMEIDA, HENRIQUE; SABATINI, SEBASTIAN EDUARDO; GENOVESE, GRISELDA

Montevideo

Congreso; SETAC Latin America 15th Biennial Meeting; 2023

SETAC

Trace metals may bioaccumulate in soft tissues of aquatic biota and cause toxic effects. Bivalve gills regulate gas exchanging and particulate filtering besides functioning as a barrier for pathogens and pollutants, while digestive glands are involved in intracellular digestion and detoxification. We studied the histopathological impact of metal pollution in M. platensis in two sites at the north coast of Patagonia, Argentina. Trace metal concentrations were quantified in water of the Port of San Antonio Este, and a reference site, Isla Mejillón, also a common locale of mussel extraction. Metal concentrations in water and organs were measured using atomic absorption spectrometry. To observe effects histologically, gills and digestive glands were dissected, fixed and prepared for routine techniques and lipofuscin detection with the Nile blue method. Histological and morphometrical alterations were registered. Higher concentrations of chromium, nickel and zinc in water were registered in the harbor, along with copper and chromium in gills and digestive gland of M. platensis in this site. Mussels from the harbor area had dilated hemolymphatic vessels with numerous hemocytes in the gill filaments. Fused filaments were also found. Morphometric analysis of the gill filaments showed an enlargement in the epithelial thickness in areas responsible for interfilament union and gas exchange. Furthermore, the area whose dominant cells are mucocytes showed a marked reduction of the epithelial thickness, likely due to metal expulsion with mucus. Digestive glands of port mussels significantly accumulated lipofuscin granules within the absorptive cells, accounting for lipid and protein peroxidation; these granules were not found or were scarce in the digestive gland tubules of mussels collected at the reference site. The metal accumulation results found in both organs along with the histopathological alterations observed evidenced its negative effects on individuals of M. platensis inhabiting the harbor area of Port San Antonio Este Therefore, we recommend the use of the histopathological essays applied in this study as biomarkers to improve the evaluation of metal accumulation effects over the health status of Mytilus platensis in aquatic environments under intense human activity.