Nitrogen excretion in the tuatara, Sphenodon punctatus

Abstract

1. 1. The nitrogen excretory pattern of the tuatara, Sphenodon punctatus, has been determined under conditions of varying protein intake and the distribution and activities of the enzymes responsible for the main excretory products are reported. 2. 2. The tuatara excretes semi-solid deposits that are almost pure uric acid. In addition it eliminates a liquid portion containing urea (80 per cent of total nitrogen), ammonia (10 per cent) and minor amounts of uric acid, creatinine, creatine and amino acids. 3. 3. With increasing protein intake there is an increase of nearly threefold in the amount of urea excreted and a concomitant decrease in the amount of uric acid and ammonia excretion. 4. 4. The tuatara possesses the enzymes of the urea cycle localized in the lover. Xanthine oxidase occurs in the kidney and glutaminase occurs in both liver and kidney. 5. 5. The importance of diet as a factor causing variation in the nitrogen excretory pattern of reptiles is discussed.