Y Chromosome Research (2006) 14:859 880 # Springer 2006 DOI: 10.1007/s10577-006-1095-9 Evolution of the karyotype and sex chromosome systems in basal clades of araneomorph spiders (Araneae: Araneomorphae) Jirˇ´ı Kra´l1*, Jana Musilova´1, Frantisˇek Sˇt_a´hlavsky´1,2, Milan Rˇ eza´cˇ1,2,Zu¨beyde Akan3, Robert L. Edwards4, Frederick A. Coyle5 & Carles Ribera Almerje6 1Laboratory of Arachnid Cytogenetics, Department of Genetics and Microbiology, Faculty of Sciences, Charles University in Prague, Vinicˇna´ 5, CZ-128 44, Prague 2, Czech Republic; Tel: +420-221-951-737; Fax: +420- 221-951-724; E-mail:
[email protected]; 2Department of Zoology, Faculty of Sciences, Charles University in Prague, Vinicˇna´ 7, CZ-128 44, Prague 2, Czech Republic; 3Department of Biology, Faculty of Art and Science, Gaziantep University, 27310 S¸ahinbey, Gaziantep, Turkey; 4Box 505, Woods Hole, MA, 02543, USA; 5Department of Biology, Western Carolina University, Cullowhee, NC, 28723, USA; 6Departament de Biologia Animal, Facultat de Biologia, Universitat de Barcelona, Avinguda Diagonal, 645, E-080 28, Barcelona, Spain *Correspondence Received 2 July 2006. Received in revised form and accepted for publication by Herbert Macgregor 20 October 2006 Key words: Araneae, diffuse stage, holocentric, karyotype evolution, meiosis, sex chromosomes, spiders Abstract Concepts of spider karyotype evolution are based mostly on advanced and most diversified clade, the entelegyne lineage of araneomorph spiders. Hence the typical spider karyotype is supposed to consist exclusively of acrocentric chromosomes including the multiple X chromosomes. However, our data show considerable diversity of chromosome morphology and sex chromosome systems in basal clades of araneomorphs. Karyotypes of basal araneomorphs consist of holocentric (superfamily Dysderoidea) or normal chromosomes with localized centromere.