Aquatic Respiration: An Unusual Strategy in the Hellbender Cryptobranchus alleganiensis alleganiensis (Daudin)

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Abstract
Separate and simultaneous determinations of aerial and aquatic gas exchange in the giant salamander, Cryptobranchus alleganiensis alleganiensis (Daudin) were made at 5°, 15°, and 25°C. The aquatic respiration of this animal accounts for over 90 percent of the total volume of oxygen consumed and 97 percent of the total volume of carbon dioxide released at all temperatures. The lungs of these individuals are large transparent sacs which are poor respiratory organs; the lungs probably function more as hydrostatic structures than as gas exchangers. This animal is the largest aquatic vertebrate that lacks gills and yet utilizes almost exclusively an aquatic mode of respiration. Specialized cutaneous modifications, a unique body form, and a peculiar behavioral mechanism are of considerable adaptative significance, and confer to the skin the effectiveness of a veritable "gill."