Ref ID : 2852
Manfred Wanner; A Review on the Variability of Testate Amoebae: Methodological Approaches, Environmental Influences and Taxonomical Implications. Acta Protozoologica 38:15-29, 1999
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Testate amoebae play an important role in terrestrial and aquatic ecosystems in regards of abundance, biomass, and energy turnover. They respond quickly to alterations in their environment either by changes in community structure or shell morphometry. This paper reviews methodological, ecological, and taxonomical aspects of environmentally influenced shell morphology with emphasis on intraspecific variability. Data from common taxa of testate amoebae, e.g., Arcella spp., Centropyxis spp., Cyclopyxis spp., Difflugia spp., Euglypha spp., and Trinema spp., are presented. It is emphasized that for ecological and taxonomical reasons the range and form ("genetic", "nongenetic") of variability within a given taxon must be known. For this purpose both, morphometrical investigations on field populations and laboratory experiments on clonal cultures will be necessary, to ensure a detailed statistical analysis of reactions, adaptations and interactions to and between several environmental factors (e.g. moisture, food, temperature, fertilizers and pesticides). As an example, it is shown that shell and apertural size of Cyclopyxis kahli is mainly affected by food and temperature. Experimentally induced changes in shell morphometry seem to be highly reversible occurring rapidly after a few binary fissions of the amoeba. In spite of the exceptional experimental conditions, neither pronounced alterations in shell morphology nor an exceeding of the shell size range of the respective "wild" taxon could be observed. This applies to all clones and taxa investigated (e.g. Trinema spp., Euglypha spp., and Cyclopyxis spp.). New possibilities in bioindication may be conceivable based on rapid changes in shell morphometry, but taxonomical problems may arise because separation of closely related taxa depends largely on shell size, demanding for additional taxonomic features for separation.