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Journal of Experimental Biology 33,542-553 (1956)
Published by Company of Biologists 1956

Cellulose Digestion By The Silverfish Ctenolepisma Lineata

REUBEN LASKER ¹ and ARTHUR C. GIESE ¹

¹ Department of Biological Sciences, Stanford University, Stanford, California

1. The silverfish, Ctenolepisma lineata, on a diet of cellulose alone shows a respiratory quotient of close to unity, indicating utilization of carbohydrate, presumably derived from cellulose.

2. The silverfish may gain weight temporarily on a diet of cellulose alone although the diet is not satisfactory for prolonged feeding.

3. The silverfish digests part of the cellulose ingested, the utilization efficiency being comparable to that of the dairy cow.

4. Silverfish fed cellulose uniformly marked with ¹⁴C respire ¹⁴CO₂, indicating that cellulose is metabolized and therefore must have been digested.

5. The gut of the silverfish contains many micro-organisms, but none of the bacteria grown in favourable culture media are capable of digesting cellulose. A few moulds do, but they are never seen growing in the gut and are presumably developed from spores grazed from wood by the silverfish.

6. Bacteria-free silverfish were obtained by washing eggs in a solution of mercuric chloride and ethanol and raising the nymphs on rolled oats and vitamins under aseptic conditions.

7. Bacteria-free silverfish fed cellulose uniformly marked with ¹⁴C respire ¹⁴CO₂, indicating that even in the absence of micro-organisms, C. lineata metabolizes cellulose and therefore must have digested it.

8. A cellulase was demonstrated in extracts of the midgut. A cellobiase and an amylase were also shown to be present. The pH optima for the cellulase are 4.0 and 6.0, with a smaller peak occasionally showing at 7.7. For cellobiase the optima were 4.5 and 6.5.

9. The cellulase was isolated in the 60 and 70% ammonium sulphate saturated fractions of the soluble proteins from the midgut.

Note:

We are indebted to Dr S. Abraham (University of California, Berkeley) for his generous gift of radioactive cellulose, and to Dr E. L. Tatum for the generous loan of equipment for radioactivity measurements and advice on its use.

Public Health Service Research Fellow of the National Cancer Institute.