Imagenes de valvas de Eucallista purpurata (Bivalvia), Cuaternario GSM y MDQ

Abstract

In high-energy habitats, seasonal storms can cause disturbances that affect the quality and stability of benthic assemblages by disturbing organisms from their life positions. Pleistocene Eucallista purpurata (Class Bivalvia) from San Antonio Bay (SAB, 40°49′S; 64°50′) vary in shell size and shape to those from the Holocene. This variation could be related to burial behavior, increasing efficiency in higher-energy environments, which are interpreted as open-sea habitats. In contrast, Holocene and modern beaches located inside the gulf are interpreted as protected environments. This species also inhabits the inner shelf of Mar del Plata (MDQ, 38°00′S; 57°33′W), an open-sea environment affected by seasonal storms, which provides an excellent opportunity to test this hypothesis. The aim of this study is to correlate the variability of E. purpurata shell shape in relation to coastal environments with different levels of energy. Geometric morphometric methods were used to analyze landmark data on shell size and shape in both modern and Pleistocene open-sea environments as well as in the protected gulf environment. We observed that shells from Modern SAB were larger and had a more marked lunule than MDQ and Pleistocene SAB shells. This is likely to be related to the energy regime of the bivalve's living environment. A more conspicuous lunule would enhance mechanical stability in areas subjected to strong tidal currents and extended periods of exposure at low tide, even though SAB is situated in a gulf characterized as a protected environment. This analysis of shell shape offers a long-term record illustrating how the morphology of E. purpurata has responded to environmental changes over the past 200,000 years, which could serve as a valuable record for Conservation Paleobiology.