Physiological and genetic differentiation in intertidal and subtidal limpets at the Antarctic Peninsula

DORIS ABELE; RICARDO SAHADE; CHISTOPH HELD; M. CARLA DE ARANZAMENDI; E WEIHE; KEVIN PÖHLMANN

San Petesburgo, Rusia

Congreso; Scientific Committee on Antarctic Research (SCAR) Meeting; 2008

The Antarctic limpet Nacella concinna (Strebel 1908) is one of the most conspicuous and abundant macrofauna components on intertidal rocky shores of the Antarctic Peninsula and the West Antarctic archipelagos. Limpets in the intertidal appear of extraordinary tolerance towards environmental fluctuations. They resist thermal extremes, functional hypoxia, and fresh water exposure during low tides. Nacella concinna represents an interesting model organism for the understanding of how the rapid environmental changes currently affecting Western Antarctica can drive evolution: All populations studied so far have evolved an intertidal migratory and a subtidal stationary ecotype, which can be distinguished by shell morphometrics. It is presently unclear whether or not morphological and behavioural (migration) differences are adaptive, and whether there is a genetic basis to the different ecotypes. We have been running stress experiments with limpets from both subpopulations collected in Potter Cove, King-George Island, including hypoxia and air exposure for up to 24 hrs. We found distinct physiological and behavioural changes with respect to internal Po2 adjustment in shell water, maintenance of cellular energetics, redox potential and tissue antioxidant levels upon stress exposure, which indicate intertidal and subtidal limpets differ significantly in their adaptive response. This is corroborated by first results we obtained from studies of the molecular pathway of hypoxic signalling in both ecotypes. Analysis of molecular markers (ISSR: inter simple sequence repeats) indicate functional differentiation may be backed by genetic segregation of both limpet subpopulations. Other markers including polymorphic microsatellites are currently developed in order to confirm or disprove this assumption.