Histological characterization and morphological alterations in gill and digestive gland in non-native bivalve from the Province of Buenos Aires: Spatial and seasonal evaluation

Morphological alterations of the gill and digestive gland were studied in Magallana gigas from areas with different degrees of human activity over one year. For that, the height of the plicas and filaments of the gill and the mean epithelial thickness were measured, the ratio of cell type and tissue composition analyzed of the digestive gland as well as alterations in the pattern of structural organization in these organs were assessed. The specimens were collected in November 2021, and February, May and August 2022 from two representative sampling sites of distinct anthropic pressures in the coastal area of Buenos Aires Province: Arroyo Parejas (AP, 38° 55′ S, 62° 04′ W) and Pehuén-Có (PC, 39° 01′ S; 61° 32’ W). The results of the morphological parameters, ratio of cell-type, tissue composition, and histological alterations of M. gigas showed differences between the studied areas and seasons, suggesting a negative relationship between human activity and the health of the gills and digestive gland of the oyster. Understanding the gill and digestive gland morphology of oysters, as well as their response to varying levels of human activity in the study region, could help mitigate the impacts of this non-native species.