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Volume 44 - Number 1 - 2009


Acid-base balance during air exposure in the bivalve mollusk Perumytilus purpuratus (Lamarck, 1819) (Bivalvia: Mytilidae)

Luis A. Montecinos1, José A. Cisterna1, Cristian W. Cáceres1 y Gonzalo S. Saldías2


1Departamento de Ecología Costera. Facultad de Ciencias. Universidad Católica de la Santísima Concepción. Casilla 297, Concepción, Chile

2Departamento de Oceanografía,. Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Casilla 160-C, Concepción, Chile




For effects of tidal rhythms, intertidal bivalves are exposed to prolonged daily emersion periods during low tide. As a response to air exposure, the mussel Perumytilus purpuratus (Lamarck, 1819) closes its valves and shifts its metabolism to anaerobic pathways by the interruption of the oxygen flux. Consequently, body fluids low their pH causing the CaCO3 disolution of the shell, which would act as a pH buffer. In this study, the role of shell CaCO3 in the regulation of internal homeostasis at different periods of aerial exposure was evaluated. We measured the variation of pH, Ca2+ and HCO3- concentrations in the extrapallial cavity and Ca2+ concentration at the shell of P. purpuratus individuals from the low and high intertidal zones. The results show that pH increases in the extrapallial cavity fluids during the emersion period in the laboratory, followed by a decrease of the shell Ca2+. Ca2+ and HCO3- concentrations did not show a significant variation in extrapallial fluids during the aerial exposure periods. Moreover, significant differences were found in the Ca2+ and HCO3- concentrations at the extrapallial fluids between individuals from low and high tidal levels. However, in the majority of measured variables, in spite of acclimation period, the basal levels were different between individuals from the low and high intertidal zones, suggesting physiological differences due to genetic differences among organisms inhabiting both zones


Key words: Anaerobic metabolism, emersion periods, intertidal zone, central Chile



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