Type of humus

Characteristic species

Ratio of full and empty shells

Characteristic species


Centropyxis plagiostoma Centropyxis constricta Centropyxis elongata Plagiopyxis minuta Geopyxella sylvicola Paraquadrula spp.


Urosomioda agilis Urosoma spp. Hemisincirra filiformis Engelmanniella mobilis Grossglockneria hyalina Colpoda elliotti

Moder and Mor

Trigonopyxis arcula Plagiopyxis labiata Assulina spp. Corythion spp. Nebela spp.


Frontonia depressa Bryometopus sphagni Dimacrocaryon amphileptoides

From Foissner, 1987a.

From Foissner, 1987a.

mon with other protozoa, ciliates have resistant or encysted forms from which they can emerge when conditions become favorable for growth and reproduction, with the presence of suitable food sources (Foissner, 1987a). Ciliates, along with flagellates and naked and testate amoebae, can quickly reproduce asexually by fission. The flagellates, naked amoebae, and testacea can reproduce by syngamy, or fusion of two cells. For the ciliates, sexual reproduction occurs by conjugation, with the micronucleus undergoing meiosis in two individuals, and the two cells joining at the region of the cytostome and exchanging haploid "gametic" nuclei. Each cell then undergoes fission to produce individuals, which are genetically different from the preconjugant parents (Lousier and Bamforth, 1990).

As noted above for the testacea, some genera of ciliates are considered indicative of acid humus, and others more typical of higher-pH or "mild" humus. See Table 4.1 for species characteristic of mull and mor soils.

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