THE ARGINASE ACTIVITY OF THE TISSUES OF THE EARTHWORMS LUMBRICUS TERRESTRIS L., AND EISENIA FOETIDA (SAVIGNY)

Cohen & Lewis (1950) found that the arginase activity of the tissues of Lumbricus was related to the output of urea by intact worms, being much higher in fasting than in feeding individuals. This implies that the earthworm may produce excretory urea by the Krebs-Henseleit mechanism (Krebs, 1934) or by some variant of it. In general invertebrates are not ureotelic and it has been suggested (Hunter & Dauphinee, 1925; Baldwin, 1953, pp. 305, 321) that they lack enzymes for the Krebs-Henseleit mechanism. Earthworms therefore are particularly interesting in this connexion. Living Eisenia foetida produce less urea per unit weight than Lumbricus, when fasting, and show a smaller change in its output between the fasting and feeding conditions (Needham, 1957), so that the species provides suitably contrasting material on which to extend the experiments of Cohen & Lewis. The arginase activity of homogenates of its tissues, i.e. the rate of liberation of urea from added arginine, has therefore been measured, under fasting and feeding regimes. The tissues of Lumbricus have been studied under the same conditions, in order to com-pare the species differences in arginase activity with those in urea output by the intact worms (Needham, 1957). Cohen & Lewis found a very high arginase activity in the gut tissue of Lumbricus and very low activity in the body wall, or 'carcass', and the two components there-fore have been separated for study in the present experiments also. METHODS For each experiment a single individual of Eisenia was used, or a portion of Lumbricus of comparable weight, between 200 and 300 mg. The worms were killed by immersion in 10 % ethanol for 5 min. at room temperature. They were freed of superficial fluid and mucus, and weighed. The body wall was opened longitudinally and pinned out. The septa were broken down and coelomic fluid absorbed with filter-paper. The gut was opened along its length and the contents mopped away with damp filter-paper. It was then dissected out from the body wall and both placed on dry filter-paper for 1 min. to remove adherent fluid, before weighing. In fasting Lumbricus gut and body wall weighed 12-6 and 487%