Ref ID : 2306
O.W. Heal; Observations on the Seasonal and Spatial Distribution of Testacea (Protozoa: Rhizopoda) in Sphagnum. J.Animal Ecology 33:395-412, 1964
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1. Seasonal study shows that for three species of Testacea (Hyalosphenia papilio, Amphitrema flavum and Nebela tincta sensu lato), peak numbers occur between May and October, followed by encystment or death. Hyalosphenia papilio, which contains symbiotic zoochlorellae, has a seasonal curve related to its light requirements. 2. The reproductive rate of large Testacea in laboratory cultures was about one division/8 days and field evidence suggests that they have few, probably much less than ten generations per year. Thus these forms, unlike other Protozoa, are unable to increase rapidly in numbers in response to sudden improvements in environmental conditions. 3. The total number of active individuals for the three species, during summer months, was 30.2x10E6/m2, with biomass, excluding test, of 1.0 g/m2 (live weight). 4. Ninety-eight species and varieties were recorded from six fen and bog sites in central and southern Great Britain. The distribution, similar to that in northern fens and bogs, is shown in Table 2. 5. Field observations, supported by experiments with Difflugia tuberculata, indicate that of the possible factors separating fen and bog-pool species, the chemical composition of the water, particularly pH, is more important than the availability of food or of detritus for the construction of tests.