Problems of nitrogen catabolism in invertebrates

I. INTRODUCTION. IN the livers of animals having a ureotelic metabolism, as Clementi [1915; 1918] has pointed out, the enzyme arginase is present, whereas those which have a uricotelic metabolism do not possess it. This principle, though valid for members of the vertebrate phylum, has not as yet been successfully extended to the invertebrates owing to certain serious difficulties. Firstly, arginase seems to be rare in its occurrence among such animals (further work upon this distribution is now in progress); secondly, few invertebrates excrete notable quantities of urea. Clementi [1918] has examined the hepatopancreas of Astacus fluviatilis and Helix pomatia and the whole bodies of termite larvae, while Hunter and Dauphinee [1924] have further studied the caecae of a starfish (Pisaster), the hepatopancreas of Cancer and the digestive glands of a clam (Saxidomus). All these organs, with an exception in the case of Helix, proved to contain no detectable amounts of arginase. Perhaps this is not surprising, since many invertebrates rely upon argininephosphoric acid for their muscular activity [Meyerhof and Lohmann, 1928; Meyerhof, 1928; Needham et al., 1932], s0 that high concentrations of arginase might be incompatible with the efficiency of the muscle.