The Absence of a Cellulase in Limnoria

Abstract

OWING to the almost invariable presence of fragments of wood in the stomach and gut of the woodboring isopod, Limnoria lignorum, it has been assumed that this animal is capable of digesting cellulose. Thus Calman (Brit. Mus. (N.H.) Economic Series No. 10) states: “Limnoria certainly swallows, and probably digests, the wood which it gnaws away to form its burrow, but it is not known whether it has any other source of nourishment.” In a report on the Marine Piling Investigation, published in the Bulletin of the American Railway Engineering Association (vol. 28, No. 290, Oct. 1926), the definite statement is made that “the main food of the limnoria is the wood into which it bores.” No experiments on the digestive powers of Limnoria appear to have been made, and it is never advisable to draw definite conclusions as to the food of any animal from the contents of its stomach, for a great deal of material may be passed through the gut which cannot be acted upon by the digestive enzymes. Though it is known that wood is ingested intracellularly by Teredo which, as shown by Harington (Biochern. Jour., vol. 15, p. 736) and Dore and Miller (Univ. Calif. Publ. Zool., vol. 22, p. 383), possesses a cellulase, it by no means follows that a similar enzyme is present in the crustacean, Limnoria, in which both the alimentary system and mode of digestion are totally different.