The American spiny-cheek crayfish, Orconectes limosus, was first introduced into European waters in 1890. The first literature record about the occurrence of O. limosus on the territory of the Czech Republic was published almost 100 years later -in 1989. The presence of this species in Czechia, however, was first recorded already in the 1960s, when crayfish were observed in the dead arms and pools adjacent to the river Elbe (Labe) in Central Bohemia. In the following few decades the spiny-cheek crayfish has spread into several larger rivers of the Elbe watershed and some of their smaller tributaries. The eastern part of the country (mostly belonging to the watershed of the river Morava) has not yet been colonised by this species. O. limosus can be found in lower reaches of a number of watercourses of a low stream order, but does not seem to penetrate far upstream in such localities. Its distribution in standing waters is largely the result of intentional humanmediated translocations. The long-term coexistence of Orconectes and native crayfish species has not yet been recorded, although both introduced and native crayfish at least occasionally come into contact. As O. limosus is a major carrier of the crayfish plague on the Czech territory, and crayfish plague outbreaks have been recently recorded, the dynamics of Orconectes invasion deserves careful monitoring in the future. Key-words:Orconectes limosus, spiny cheek crayfish, invasive species, distribution, crayfish plague, Czech Republic. DISTRIBUTION DE L'ÉCREVISSE INVASIVE (ORCONECTES LIMOSUS) EN RÉPUBLIQUE TCHÈQUE. PASSÉ ET PRÉSENT RÉSUMÉL'écrevisse américaine, Orconectes limosus, a été introduite en Europe en 1890. Les premiers écrits relatant la présence d'O. limosus sur le territoire de la République tchèque ont été publié presque 100 ans plus tard, en 1989. Cette espèce a déjà été observée en Tchéchie cependant, dans les années 60, dans les bras morts et les plans d'eau adjacents à la rivière Elbe (Labe) en Bohème centrale. Dans les décennies suivantes, l'écrevisse américaine a colonisé d'autres grands cours d'eau du bassin de l'Elbe, et quelques-uns de leurs plus petits affluents. La partie orientale du pays (correspondant principalement au bassin de la rivière Morava) n'a pas encore été colonisée par cette espèce. O. limosus est présente dans les parties les plus basses d'un certain nombre de cours d'eau d'ordre hydrographique faible, mais elle ne semble pas remonter très en amont des cours d'eau. Sa répartition dans les eaux calmes est largement le résultat des transports effectués par l'homme. La coexistence au long-terme d'Orconectes et des espèces natives d'écrevisse n'a pas encore été établie, bien que les écrevisses natives et les écrevisses introduites se retrouvent au moins occasionnellement en contact. L'écrevisse O. limosus étant le principal vecteur de la peste de l'écrevisse sur le territoire tchèque, et des cas de peste de l'écrevisse ayant été récemment enregistrés, la dynamique de l'invasion de l'Orconectes doit être soigneuseme...

The objective of this article is the regional differentiation of rural space in Czechia, which is defined as the territory of rural municipalities of up to 3,000 inhabitants. The ultimate determination of particular types of rural space is realized at the level of authorized municipal authorities. Current socioeconomic characteristics of rural municipalities in Czechia are compiled and used for analysis. These characteristics were selected on the basis of their potential to represent important socioeconomic phenomena, processes and factors that are typical for the Czech countryside and that influence the development of rural municipalities. Four statistically significant components are identified through the statistical analysis of the indicated data at the level of authorized municipal authorities, namely: size, growth, human potential and housing. Different combinations of these components enable us to define eight main types of rural space, in terms of potential for development. This provides evidence to confirm our affirmation that rural space in Czechia is not homogenous. The results of the statistical analyses conducted also show that the basic differentiation of the Czech countryside is determined by the geographical location of particular areas.

The refractive index of the ternary compound Hg1–xCdxTe is measured over a large energy region for several alloy compositions x between x = 0.18 and 1.0 at room and liquid nitrogen temperatures. The experimental results are compared with two theoretical models and with the Sellmeir equation. The analytical expression describing the compositional dependence of the refractive index is derived by fitting the compositional dependence of Sellmeir coefficients.

Abstract