They provide a "natural environment" for experimental and descriptive analyses. Hence in this chapter some specific methodological problems will be highlighted concerning the analysis and interpretation of variabiliy in testate amoebae. The basic methodological tools for collecting, preparation, observation and statistics have been discussed in detail by Bonnet (1964), Schonborn (1966), Laminger (1980), Foissner (1987, 1994), Wanner (1991), Aescht and Foissner (1995), and Dunger and Fiedler (1997). (1988) observed that Testaceafilosa have wider ranges in morphometric variation as compared with Testacealobosea. Based on a biometrical analysis of twenty-four soil testate amoebae, Luftenegger et al. lobose and filose testates) may have a different autecology with individual importance for bioindication. (1992) pointed out that taxa of different origin (e.g. This is supported by community structure and biometric data. At present, naked and testate filose amoebae are grouped within the (revised) phylum Rhizopoda, while naked and testate lobose amoebae are grouped into a separate (revised) sarcodine phylum, the Amoebozoa (Cavalier-Smith 1997). This view is strongly supported by molecular data (Bhattacharya et al. The major characteristics, the shell and the pseudopodia, evolved independently representing only convergent features (Hausmann and Hulsmann 1996). Testate amoebae are a polyphyletic, or at least biphyletic, assemblage. There are four main shell types: proteinaceous (species with a flexible or rigit shell), calcareous (only two genera), siliceous (species which secrete their own regular siliceous shell platelets, so-called "idiosomes"), and agglutinate (species which include extraneous mineral particles in their shell structure, so-called "xenosomes"). A poteinaceous organic matrix is the basic shell component, either solely or functioning as cement, fixing particles in position (Moraczewski 1969 Saucin-Meulenberg et al. The shell encloses the cell plasma and has usually a single aperture for the pseudopodia. On the other hand, a strong influence of environmental factors on shell morphometry would lead to serious taxonomic problems, because classification of closely related testate amoebae is primarily based on these characteristics. Therefore a complete understanding of intraspecific variation is necessary before we are able to separate between possible species." Is for instance the phenomenon of ecomorphosis, the variation caused by the environment (expressed by changes in shell morphology) not only measurable, but also reproducible or even reversible within a few generations? If so, this would give new and fascinating tools for bioindication with testate amoebae, in the laboratory as well as in the field. Furthermore, he stated that "differences between groups of similar specimens ("phena") may reflect either a speices difference or intraspecific variation. As stressed in Mayr (1969), "the underestimation of individual variation may have caused more than 50% of all synonyms". For taxonomical and ecological reasons it is important to estimate the range and form ("genetic", "nongenetic", as defined in Mayr 1969) of variability within a given taxon. Physical limitations, like diffusion-dependent cells size range, surface tension, or biomechanical preconditions of protists skeletons (see Rhumbler 1898 Vogel and Gutmann 1988 Fenchel 1990) and ecological constraints, like habitat adaptation, will also influence the shape of the amoebae shell, resulting in a great variety of different morphs. shell type and shape, spikes, spines, diaphragms, the aperture) has been commonly used of differentiate between genera or species. The shell architecture of testate amoebae (e.g. Wanner and Meisterfeld 1994 Wanner 1994, 1995). They respond to modified conditions by altering abundance or dominance structure (Lousier 1974 Foissner 1987, 1997) and by changing their shell morphometry (e.g. Testate amoebae are particularly suitable for the fundamental question, whether and how an organism responds to changing environments. Review on the Variability of Testate Amoebae Echinopyxis, Homoeochlamys),Įuglyphinopsis Frenzelina Geamphorella, Hedley, "An Atlas of Freshwater Testate Amoebae"Ĭopyright: The Natural History Museum, LondonĪnd we thank following scientists and The Society of Protozoologists (The Journal of Protozoology) for quoting text descriptions from their papers.Ĭentropyxis (Syn. We reproduce the descriptions of morphology from following books Ĭopyright: CHARLES C THOMAS PUBLISHER, LTD., 1966Ĭ.G.
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