The Abundance and Micro-Distribution of Testate Amoebae (Rhizopoda:Testacea) in Sphagnum

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Abstract
Thirty species of Testacea were shown to have an extremely patchy horizontal distribution within a relatively uniform sward of Sphagnum recurvum. and a well-defined vertical distribution of Testacea on Sphagnum and their distribution in wet and dry habitats. In nearly all species, dead individuals (empty tests) reached their maximum in a lower zone than the living individuals of the same species. Three species possessed zoochlorellae. Two of these, Hyalosphenta papilio and Amphitrema flavum, were largely restricted to the upper 6 cm of Sphagnum, probably because of light requirements. The third species, A. wrightianum reached maximum numbers 4-10 cm down the plant and this may represent a balance between light requirements and the availability of peat and mineral particles for test construction. Of the forms without zoochlorellae, Assulina muscorum occurred mainly in the top 6 cm, Nebela tincta was fairly evenly distributed and the remaining twenty-five species all showed maxima in the lower levels. Evidence suggests that H. paptlio and N. tincta react to adverse environmental mental conditions by encysting rather than by migrating. Peat and mineral particles on Sphagnum increase with depth and Testacea requiring these for their tests are largely restricted to the lower levels. Bog habitats contain little mineral matter and species using this in their tests are found mainly in fens. The number of Testacea in a Sphagnum sward is estimated at 16,000,000 per m2 with a biomass of about 1 gr/m2. About 20,000,000 dead individuals (empty tests) per m2 were recorded.

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