AN UPDATED COMPILATION OF WORLD SOIL CILIATES (PROTOZOA, CILIOPHORA),WITH ECOLOGICAL NOTES, NEW RECORDS, AND DESCRIPTIONS OF NEW SPECIES

This review compiles and analyses the taxonomic and biogeographical in formation available on soil ciliates. Key literature (257 references) is tabulated for each species. Furthermore, about 500 new records are reported from hundreds of samples collected world-wide, and four new s pecies are described from Kenyan soils, including the new genus Apobry ophyllum; Metopus ovalis Kahl, 1927 is redescribed. 643 ciliate specie s were originally described or reliably recorded from about 1000 soil samples world-wide, 49 (7.6%) of them were later recognized as junior synonyms, and 78 (13.2%) have been poorly described, leaving a total o f 516 well-known species. However, the studied samples contained about 700 new species, most of which (about 500) have not yet been describe d. Thus, the total number of soil ciliates amounts to at least 1000 sp ecies. The overwhelming portion of soil ciliates belongs to three syst ematic assemblages, viz. the hypotrichs (39%), gymnostomatids (26%) an d colpodids (13%) if the undescribed species are taken into account. M ost soil ciliates feed on bacteria (39%) or are predatory (34%) or omn ivorous (20%). Some are strictly mycophagous and highly characteristic for terrestrial habitats; and a few (mainly metopids) are anaerobic. Only about one fourth of the soil ciliate species has been reliably re ported from freshwater habitats and from more than three out of five m ain biogeographical regions, indicating a high specificity of the soil ciliate biota and a limited distribution of at least some species. Th is is supported by the observation that some very conspicuous species, such as Krassniggia auxiliaris and Bresslanides discoideus, have so f ar been found only in Gondwanan, respectively, Laurasian soils.