Carbon dioxide output in the respiration of three Pisidium species (Bivalvia, Sphaeriidae)

The carbon dioxide output in respiration of Pisidium casertanum, P. henslowanum and P. conventus was studied in the laboratory. A closedbottle method was used, and the amount of dissolved inorganic carbon was measured with an infrared gas analyser. The mean value of the constant b in equation R=aW ^b, where R is the respiration rate and W the ash-free dry weight of the animal, was ca. 0.75 in both the eurytherm P. casertanum and the cold-stenotherm P. conventus at five temperatures, but the temperature dependence of b was opposite in these species. The temperature dependence of metabolism increased with increasing size in P. casertanum and P. henslowanum but decreased in P. conventus. A 'reversed acclimatization pattern' was found, where the metabolism rate and its temperature dependence was lower in the cold-adapted stenotherm species.