Nestling behavior of Pleistocene Hiatella from southern Beagle Channel coast

GORDILLO, S. PONCE J.F.

Valdivia, Chile

Congreso; VII Congreso Latinoamericano de Malacología; 2008

Fossil and living Hiatella exhibits great plasticity in its habitat and mode of life, and its shell is highly variable in both shape and size. Hiatella is able to bore, nestle or live bysally attached to other epifauna or substrates. It was suggested (Strauch, 1968) that shell length of Hiatella is inversely related to winter temperatures and consequently, it is useful in the estimation of Cenozoic paleotemperatures. However, other authors (Rowland and Hopkins, 1971) believe that the mode of life of each population is what regulates the size of the individuals. In this regard, the objective of this study is to analyze different potential factors controlling the size of Pleistocene Hiatella from a raised marine terrace located in Navarino Island, southern Beagle Channel. In order to reconstruct paleoenvironmental conditions, and to evaluate paleoecological aspects, the stratigraphic section and the main taphonomic and ecological features of the fossil assemblage were analyzed. Our findings were compared to previous records of living and fossil Hiatella. Results suggest shallow marine paleoenvironments characterized by strong bottom currents. The Pleistocene assemblage is well preserved and dominated by sessile suspension feeders. Hiatella was found within empty tests of barnacles which apparently served as microenvirnonments for this species. In this assemblage, Hiatella shells are short and deformed. Contrarily, extant nestling Hiatella specimens living partly buried in sandy substrates are larger and exhibit more oval-oblong shape than byssally attached forms in the rocky substrates. This may be because they can fully develop. Studying new and previous data, we contrasted the two hypotheses concerning the use of Hiatella in the estimation of Cenozoic paleotemperatures. It is concluded that size and shape of shells of Hiatella from the Beagle Channel primarily reflect the living habits of the animal, although on a broader scale a control by temperature cannot be ruled out.