[Previous IPC6 abstract]
ENDOLITHIC POLYCHAETA IN ROCKY SHORES NEAR MAR DEL PLATA, ARGENTINA: DISTRIBUTION AND ABUNDANCE
Ferrero, L.1; Obenat, S.2 & Spivak, E.2
1 Centro de Geología de Costas y el Cuaternario, Argentina
2 Departamento de Biología, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata Funes 3250, 7600 Mar del Plata, Argentina
Rocky shores are usually considered two-dimensional environments. However, several polychaete, sipunculid and bivalve species can excavate some types of hard substrata and live in galleries or burrows. The aim of this contribution is to identity and quantify the endolithic polychaeta that live in a rock shoal (abrasion platform) in Mar de Cobo, Argentina (37°45'S, 57°56'W). This platform consists of continental pleistocene deposits and is exposed to air only during extraordinary low tides (tidal amplitude ~ 0.80 m). Differences in composition, granulometry and cohesion of the sediments caused that the platform has been diferentially eroded and, as a consequence, it shows a high number and variety of microenvironments. The most abundant polychaete worms found in this habitat belonged to three families: Nereidae, Spionidae and Syllidae. Among the nereids, we found Neanthes succinea, a species previously known to inhabit only estuarine muddy sediments and Ficopomatus enigmaticus reefs in Mar Chiquita, a coastal marine lagoon that flows into the ocean 5 km north from Mar de Cobo, and other estuarine habitats. Among the Spionidae and Syllidae, we found one species of Polydora and one of Syllis. These species coexist with other endolythic invertebrates: Themiste petricola (Sipuncula), Barnea lamellosa, Pholadidea darwini and Lithophaga patagonica (Bivalvia). This platform is inhabited by crabs that found refuges on it; some species are known to be annelidophagous. It is also the foraging site for several marine birds. This research can be used as a quantitative basis for studies on the availability of alimentary items.