Studies on the urinary nitrogen waste products in south american anurans from different habitats

Abstract

1. 1. Urinary nitrogen waste excretion and urea concentration in plasma of juvenile Bufo arenarum and adult Bufo arunco, Bufo fernandezae and Leptodactylus ocellatus were studied; they are terrestrial, cave dweller and semi-aquatic species, respectively. 2. 2. The urinary NH3-N, urea-N and uric acid-N, and plasma urea concentration were measured in samples from animals fasted for 15 days and acclimated at constant temperature over 4 days before sampling. 3. 3. The percentages of urinary urea-N, ammonia-N and uric acid-N were 95.3, 4.3 and 0.12 for Bufo arenarum; 95.0, 5.0 and not determined for B. arunco; 95.3, 4.6 and 0.09 for B. fernandezae; and 91.1, 8.9 and 0.08 for L. ocellatus, respectively. 4. 4. The percentage of urinary nitrogenous compounds was shown to be independent of the habitat and of the body weight of the animals. 5. 5. Plasma urea concentration (in mM) and the U/P ratios were: 19.8 and 1.8 ( B. arenarum); 37.9 and 1.6 ( B. arunco); 19.3 and 1.8 ( B. fernandezae) and 7.6 and 5.2 ( L. ocellatus), respectively.