Showing papers in "Acta Protozoologica in 1988"

Spatial separation of terrestrial ciliates and testaceans (Protozoa): a contribution to soil ciliatostasis

Abstract: Synepsis. The vertical distribution of soil ciliates and testaceans was investigated in a spruce forest, in a meadow and at some alpine and iowland sites. A direct and an indirect (culture) method were used to count the organisms. Active ciliates are abundant in the litter (L) but low numbers occur in the F and H layer of the spruce forest. Testaceans, in contrast, reach peak numbers in the F and H horizon which causes a distinct spatial separation from the ciliates. No or very few active ciliates occur in the meadow and the other sites which have no litter layer. Cultures of air-dried and remoistened soil samples, however, nearly always yield high numbers. These findings can be explained with the concept of ciliatostasis and support the view that certain chemical substances which are present in older soils are mainly respo,nsible for the iirhibition of ciliate excystment and growth in most evolved natural soils. The annulment of ciliatostasis in cultures by drying and remoistening of the soil is perhaps achieved through the inactivation or disappearance (e.g., by evaporation) of these substances. The increased bacterial food supply lnay also be of some importance. However, under field conditions food is probably not the key factor, because food organisms (e.9., bacteria, fungi) are surely abundant in the upper layers of sites where no or only few active ciliates are found as in meadows and arable land. L;ikewise, pore space can be excluded.