title: Multivariate morphometric analyses of the predatory ciliate genus Semispathidium (Ciliophora: Litostomatea), with description of S. longiarmatum nov. spec.
abstract: We studied morphometrical variation, species boundaries, and importance of morphometric features for a reliable separation of five African Semispathidium taxa. Altogether, 20 features traditionally used in alpha-taxonomy of the predatory genus Semispathidium were measured or scored on 85 protargol-impregnated interphase specimens, and were analyzed using hierarchical clustering as well as principal component and canonical discriminant analyses. This multivariate approach confirmed that a population found in Botswanan floodplain soil represents a distinct taxon. The new species is described here as S. longiarmatum, using live observation, protargol impregnation, and scanning electron microscopy. Semispathidium longiarmatum strongly resembles S. armatum and S. breviarmatum but it is clearly distinguished from these species by the extrusome pattern. The reliability of S. longiarmatum is also strengthened, according to the canonical discriminant analysis, by several quantitative features, viz., the number of ciliary rows, the length:width ratio of the macronucleus, and the number of dikinetids in brush row 1. Moreover, the present study documents the distinctness of all African Semispathidium species which can be separated by a combination of both qualitative and quantitative (morphometric) features. Consequently, Semispathidium species do not form a continuous complex but fairly discrete clusters in the phenotypic space.
authors.affiliation: Department of Zoology, Faculty of Natural Sciences, Comenius University, Mlynská dolina B-1, SK-842 15 Bratislava, Slovak Republic. Electronic address: vdacny@fns.uniba.sk.
authors.forename: Peter
authors.initials: P
authors.lastname: Vďačný
authors.affiliation: Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 9, SK-845 23 Bratislava, Slovak Republic.
authors.forename: Marek
authors.initials: M
authors.lastname: Slovák
authors.affiliation: FB Organismal Biology, Faculty of Natural Sciences, Salzburg University, Hellbrunnerstrasse 34, A-5020 Salzburg, Austria.
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Foissner
mesh_terms: D016798:Ciliophora / Q000145:classification* / Q000648:ultrastructure*; D048648:Macronucleus / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D015999:Multivariate Analysis; D010802:Phylogeny; D012987:Soil / Q000469:parasitology; D013045:Species Specificity
chemical_list: D012987:Soil
keywords: Africa; Extrusomes; Numerical taxonomy; Resting cyst; Species discrimination