Ref ID : 2133
O.W. Heal; The Abundance and Micro-Distribution of Testate Amoebae (Rhizopoda: Testacea) in Sphagnum. OIKOS 13(1):35-47, 1962
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1. Thirty species of Testacea were shown to have an extremely patchy horizontal distribution within a relatively uniform sward of Sphagnum recurvum, but to have a well-defined vertical distribution which was not a seasonal phenomenon. There was no indication of a correlation between the vertical distribution of Testacea on Sphagnum plants 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. 2. Three species possessed zoocholorellae. Two of these, Hyalosphenia papilio and Amphitrema flavum, were largely restricted to the upper 6 cm of the 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. 3. Of the forms without zoocholorellae, Assulina muscorm occurred mainly in the top 6 cm, Nebela tincta was fairly evenly distributed on the Sphagnum and the remaining twenty-five species all showed maxima in the lower levels. 4. Evidence suggests that H. papilio and N. tincta react to adverse environmental conditions by encysting rather than by migrating. 5. Peat and mineral particles on the 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 test are found mainly in fens. 6. 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.