Lunglessness, Body Size, and Metabolic Rate in Salamanders

Oxygen consumption was measured in 10 species of lunged salamanders (Ambstomatidae, Salamandridae) and compared to values for 12 species of lungless salamanders (Plethodontidae) taken under identical conditions in an earlier study. There was no significant difference between slopes of log10−log10 regressions of standard metabolic rate against body weight for lunged and lungless salamanders at either 15 or 25 C, indicating that lunglessness in salamanders does not restrict uptake of oxygen from air. The relationship between standard metabolic rate and body size for temperate zone salamanders at 15 C is expressed by M = 40.7 W0.817, where M is oxygen consumption in μl O₂/h and W is body weight in g. Salamanders at 15 C consume less than 60% as much oxygen as other air-breathing vertebrate ectotherms under comparable conditions; this low oxygen requirement may be related to a strategy of overall energy use reduction.