Water Relations in Four Species of the Salamander Genus Desmognathus

Bickert, James

ABSTRACT: Water relations of 340 specimens of four species of Desmognathus were studied; these Included Desmognathus quadramaculatus, Desmognathus montlcola, Desmognathus fuscus and Desmognathus ochrophaeus. Specimens used came from a vide geographic area and a number of habitats. The objectives of this study were to determine the relationship of desiccation tolerances to terrestrialism for Desmognathus, and to assess the effects of temperature and photoperiod acclimations on their water balance. All experiments were carried out under conditions of controlled temperature and photoperiod. Experiments were conducted at 20C, 0 cc air flow/min. and near 0 percent relative humidity. The rate of water loss, body water composition, critical activity point (CAP) and surface/volume relation were recorded for each salamander. Water content of two of the four species of Desmognathus was significantly higher at lower acclimation temperatures. Lower acclimation temperature also significantly Increased the CAP values for all species. Animals acclimated at higher temperatures lost a greater percentage of water in a shorter period of time. A longer photoperiod increased the total amount of body water, significantly lowered the CAP value, and had no effect on the rate of water loss. Some sexual variation in body water composition was noted between males and females. The significant difference has been due to the gravid condition of females at the time of water content determinations. Interspecific differences in rates of water loss, CAP values, and other physiological factors tend to substantiate physiologically the original aquatic to terrestrial ecological series of Hairston (1949) for the salamanders of the genus Desmognathus. CAP. values were not influenced by the rate of desiccation and may be genetically controlled. CAP may have affected habitat preference of the radiating species.