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

<title>Abstract</title> The objective of this study was to characterize and evaluate morphological alterations and cell and tissue composition of the gill and digestive gland in <italic>Magallana gigas</italic>from urbanized areas with different degrees of human activity over one year. For that, the height of the plicas and filaments of the gill and the tubule epithelium area 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 <italic>Magallana gigas</italic> showed difference between the studied urbanized areas and seasons, suggesting a negative relationship between intense human activity and the health of the gills and digestive gland of the Pacific oyster. Understanding the gill and digestive gland morphology of Pacific 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.