M. Bonkowski et M. Schaefer, INTERACTIONS BETWEEN EARTHWORMS AND SOIL PROTOZOA - A TROPHIC COMPONENT IN THE SOIL FOOD-WEB, Soil biology & biochemistry, 29(3-4), 1997, pp. 499-502
Earthworms and protozoa are, in terms of biomass, the most important g
roups of soil fauna in beech forests on limestone in southern Lower Sa
xonia (Germany). To investigate the effect of high protozoan numbers o
n earthworm distribution, a multiple choice feeding experiment was set
up in fumigated soil, reinoculated with different numbers of naked am
oebae, protozoa commonly found in that soil. Distribution of Aporrecto
dea caliginosa (Savigny) after wk was correlated with numbers of amoeb
ae in soil. Other experiments confirmed digestion of protozoa by earth
worms. The weight gain of young A. caliginosa in soil with amoebae was
twice that in soil without protozoa. Direct observations of fresh cas
t material confirmed that active protozoa were digested by A. caligino
sa. Lower protozoan numbers in faeces of Octolasion lacteum (Orley) th
an in the surrounding soil were found by dilution series, indicating g
razing on the active part of soil protozoa by earthworms. The experime
nts provide evidence that A. caliginosa is actively searching for plac
es with high protozoan densities and that protozoa may play a signific
ant role in earthworm nutrition. (C) 1997 Elsevier Science Ltd.