Ambient oxygen tension, metabolic rate, and habitat selection in freshwater snails

Abstract

The relationship between ambient oxygen tension (PO 2 ) and metabolic rate (VO 2 ) in freshwater snails was examined in order to determine if habitat selection is influenced by hypoxia tolerance. Laboratory and field data were collected on 11 species from lotic and lentic habitats. Metabolic rates were determined at 15 and 25 °C using a closed respirometer technique. In 3 of 20 cases, species were judged to be metabolic O 2 conformers, in 8 of 20 to be metabolic O 2 regulators, and in 9 of 20 to have two zones of metabolic O 2 conformation, with the zone in the higher range of PO 2 being characterized by less fall in VO 2 with declining PO 2 than in the zone in the lower range of PO 2 . We conclude that the response of aquatic VO 2 to hypoxia among snails can not be predicted by any single taxonomic, ecological, or physiological classification.