Growth of the earthworm Eisenia foetida on microorganisms and cellulose

Abstract

The growth of Eisenia foetida (Savigny) (200–300 mg live weight) was measured on mixtures of inorganic salts, vitamins, and cellulose upon a base of ashed loam or sand. High concentrations of inorganic salts, exceeding an ionic conductivity of about 8mS cm −1 were detrimental, and lower concentrations failed to promote growth. Hatchlings (5 mg live wt) grew to 233 ± 14 mg (SE) on 22 species of bacteria (100 mg dry wt) at 24±1°C, in 8 weeks. There were no significant differences in growth on Gram-negative versus Gram-positive bacteria. Human pathogens were no less nutritive than non-pathogenic species. There was no growth on 6 of 19 species of fungi. Only 31% weight (70 ± 16 mg) was gained per unit weight of fungi as per unit weight of bacteria (100 mg dry microbial biomass). Worms grew as well (274 ± mg) on three species of protozoa as on 22 bacterial species. Growth on any microorganisms tested was less than on activated sludge. E. foetida doubled in weight on the fungus Coriolus hirsutus with the addition of sand or ashed loam. With either of these two forms of grit and microorganisms there was no growth. For growth, a combination of carbohydrate (cellulose), microorganisms and grit appeared necessary. Lyophilized microorganisms had to be washed free of ionic conductivity (and presumably organic residues) from their culture medium for earthworms to grow favorably.