LAUSR

Abstract Although some studies have evaluated the use of Siphonaria lessonii as a bioindicator of pollution, no study has identified the effects of human activities on the digestive gland, which is the main centre of detoxification of xenobiotics and a target organ in contamination studies. Thus, the present work aims to evaluate the use of this species as a suitable sentinel of contamination by analysing the digestive gland and shell alterations. The study was carried out in three populations exposed to different degrees of anthropogenic impact in the coast of Buenos Aires: a reference site (VG), a mid-impacted site (MPL) and a highly-impacted site (MPP). A histological analysis of the digestive gland was performed, as well as an assessment of the geometric morphometry, thickness, density and microstructure of the shell. Our results indicated that the individuals from the impacted sites present several histological alterations in the tubules of the digestive gland. These included hypertrophy and hyperplasia of different cell types (MPP), alterations of the digestive tube morphology (MPL and MPP), the presence of lipofuscin-like substances (MPL) and a high inflammatory response (MPP). In the shells, neither microstructural malformations nor changes in the elemental composition were found. However, shell morphometric variations and a decrease in shell hardness (thickness and density) were observed in the impacted sites. In conclusion, our results indicate that S. lessonii is a well-suited sentinel of contamination since the effects of anthropogenic impact may be reflected in both soft and hard structures. Although further investigations are necessary to identify the relationship between these effects and their potential causing agents, these simple and low-cost methodological approaches could be used to diagnose disturbance in the ecosystem health status where this species inhabits.