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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 2032

Wilfried Schonborn and Theodor Peschke; Biometric Studies on Species, Races, Ecophenotypes and Individual Variations of Soil-inhabiting Testacea (Protozoa, Rhizopoda), Including Trigonopyxis minuta n. sp. and Corythion asperulum n. sp. Arch.Protistenk 136:345-363, 1988

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In a raw humus soil (GDR, Thuringia) the testacean genera of Trigonopyxis, Assulina, Valkanovia and Corythion were investigated biometrically. The analyses referred essentially to measurements of shells and quantitative features of the shape of shells. With the help of significance tests and the analyses of size frequency distributions, two new species, Trigonopyxis minuta and Corythion asperulum were discovered as well as the presence of Assulina collaris Kufferath, which until now had been overlooked. (Corythion asperulum is also qualitatively characterized by fine spines). Comparisons of biometric analyses between geographically separated populations led to distinction of geographic races in Trigonopyxis arcula and Corythion dubium (statistically significant differences). In addition to geographic races ecological variations were also examined. Soil-inhabiting populations of Euglypha ciliata have shorter spines than lake-inhabiting individuals. This variation, however, is reversible (modification) and has an adaptive value: ecophenotypes. Furthermore, the analyses showed that there are size-monomorphic and size-polymorphic Testacea. Between these extremes exist many transitions. The biometric method, however, permits separation of new species or geographic races only within monomorphic genera. It could be shown that even slight genetic shifts within the range of a monomorphic character can lead to a new shell type (at the height of aperture of Trinema lineare). Directives on analyses and classifications of quantitative variations are given. Individual variations are: insignificant differences, all forms of feature spectrum of polymorphic species and also quantitative and qualitative aberrations found only a few times. Instead of naming these variations it may be better to put together a phenospectrum of the population examined. The genetic causes of the various variations are discussed.