INVESTIGADORES
PARRAS Ana Maria
congresos y reuniones científicas
Título:
Borers and encrusters as giveaways to the prescence of hermit crabs in Antarctic Eocene gastropods
Autor/es:
PARRAS, A.; CASADÍO, S.; GRIFFIN, M.; MARENSSI, S.; SANTILLANA, S.
Lugar:
Puerto Madryn
Reunión:
Jornada; Reunión Anual de Comunicaciones de la Asociación Paleontológica Argentina; 2005
Institución organizadora:
Asociación Paleontológica Argentina
Resumen:
Eocene rocks from Seymour Island, at the northern tip of the Antarctic Península, contain a record of remarkable molluscan shell concentrations representing ecosystems with no Recent parallels, as they developed in a relatively warm (c. 14°C) shallow sea in a sunlight/darkness-stressed setting. Detailed study of fossil organisms from environments no longer represented is necessary if -among other things- we are to understand the nature and degree of environmental control on their life history. We described the association of encrusting and boring organisms developed on the gastropod Antarctodarwinella ellioti Zinsmeister, from the lower section of the La Meseta Formation exposed along the northern tip of Seymour Island. The age of the rocks bearing the fossil fauna considered is middle Eocene, i.e., ca. 45 Ma. Chi square Independence Test revealed that the community of encrusting and boring organisms recorded on Antarctodarwinella ellioti -dominated by polychaetes and bryozoans- show a clear preference for the aperture interior area of the shell. A subsequent Cochran Q Test indicated that the differences in frequency of encrusting and boring organisms as counted on the different aperture interior sectors were statiscally significant. Thus, polycahetes, boring bryozoans, and encrusting bryozoans, do not show the same frequency in each sector of the aperture interior, i.e., they are more frequent on the columella. The encrusting bryozoans also appear to show higher preference -albeit not as high as on the columella- on the outer lip. This association of boring and encrusting organisms and their distribution on the shells confirms that specimens of Antarctodarwinella eliotti involved were inhabited by hermit crabs