In terms of cytogenetics, entelegyne araneomorphs are the best studied clade of spiders. The typical karyotype of entelegyne males consists of acrocentric chromosomes, including 2 non-homologous X chromosomes. The present study is focused on the karyotype, nucleolus organising regions (NORs) and sex chromosome behaviour during meiosis of the entelegyne Wadicosa fidelis (Lycosidae). Preparations stained by Giemsa were used to study karyotype and meiosis. NORs were visualised by silver staining and fluorescence in situ hybridisation with 18S rDNA probe. The male karyotype consists of 28 acrocentric elements, including 2 X chromosomes. In contrast to the majority of other spiders, the male sex chromosomes pair during the major part of meiosis. Following an initial period of parallel pairing, the attachment of male sex chromosomes is restricted to centromeric areas and continues until metaphase II. Our study revealed an enormous number of NORs in the population from Galilee and indicates a considerable variability of NOR numbers in this population. The distal regions of 9 or 10 autosomal pairs contain NORs. The obtained data indicate the rapid spread of NORs in the karyotype of W. fidelis, which was presumably caused by ectopic recombinations and subsequent hybridisations of individuals with different NOR genotypes that produced heterozygotes.

Laboratory of Arachnid Cytogenetics Department of Genetics and Microbiology Faculty of Science Charles University Prague Prague Czech Republic

References provided by Crossref.org

Advances in Understanding the Karyotype Evolution of Tetrapulmonata and Two Other Arachnid Taxa, Ricinulei and Solifugae

Karyotype differentiation and male meiosis in European clades of the spider genus Pholcus (Araneae, Pholcidae)

Atypus karschi Dönitz, 1887 (Araneae: Atypidae): An Asian purse-web spider established in Pennsylvania, USA

Insights into the Karyotype Evolution of Charinidae, the Early-Diverging Clade of Whip Spiders (Arachnida: Amblypygi)

Evolutionary pattern of karyotypes and meiosis in pholcid spiders (Araneae: Pholcidae): implications for reconstructing chromosome evolution of araneomorph spiders

Cytogenetics of entelegyne spiders (Arachnida, Araneae) from southern Africa

Morphological and cytogenetic characteristics of Neobisium (Blothrus) slovacum Gulička, 1977 (Pseudoscorpiones, Neobisiidae), the northernmost troglobitic species of the subgenus Blothrus in Europe

Molecular technique reveals high variability of 18S rDNA distribution in harvestmen (Opiliones, Phalangiidae) from South Africa

Comparison of different cytogenetic methods and tissue suitability for the study of chromosomes in Cimex lectularius (Heteroptera, Cimicidae)