Abstract
We present the results of the first study on the karyotypes of four European species of Roncus: Roncus alpinus L. Koch, 1873, Roncus lubricus L. Koch, 1873, Roncus transsilvanicus Beier, 1928 and Roncus sp. The diploid number was 2n = 23 in Roncus sp., 2n = 43 in R. alpinus and R. transsilvanicus and 2n = 45 in R. lubricus. Telocentric autosomes predominate in species with a high chromosome number and metacentric autosomes in Roncus sp. We assume that the ancestral situation for this genus is a high number of chromosomes. A low number of chromosomes is very likely a consequence of centric fusions, which have possibly played a very important role in karyotype evolution in the genus Roncus. All the species analyzed have the X0 sex chromosome system. The X chromosome is metacentric and is the smallest element in the karyotypes of all the species analyzed.
Highlights
Pseudoscorpions are an ancient phylogenetic lineage of arachnids that had developed most of their typical morphological features by the Middle Devonian (Schawaller et al, 1991)
Our study provides further information on the cytogenetics of the pseudoscorpion genus Roncus (Neobisiidae) based on a study of another four species, which extends the previous work on this genus that was based on eight species (Troiano, 1990, 1997; Zaragoza & Šťáhlavský, 2008)
The great variability in karyotype characteristic of Roncus has been recorded for several other pseudoscorpion families, e.g. Atemnidae, Chthoniidae, Chernetidae, Geogarypidae and Olpiidae (e.g. Šťáhlavský & Král, 2004; Šťáhlavský et al, 2005, 2006, 2009, 2012)
Summary
Pseudoscorpions are an ancient phylogenetic lineage of arachnids that had developed most of their typical morphological features by the Middle Devonian (Schawaller et al, 1991). With the currently recognized 25 families and more than 3500 described species they represent the fourth largest order of arachnids (Harvey, 2011) Despite this diversity, we have still only fragmentary information about the cytogenetics and karyotype evolution in this group. There are karyotype data for 49 species from 8 families (Šťáhlavský, 2013) and it is evident that there is considerable variation in number of diploid chromosomes in pseudoscorpions ranging from 7 in males of Olpium turcicum and Indolpium sp. Troiano, 1990, 1997; Zaragoza & Šťáhlavský, 2008) (Table 1) This genus of pseudoscorpions includes 138 named species and is endemic to Europe, North Africa and the Caucasus region (Harvey, 2011). The aim of this study is to add more information about Roncus chromosomes from other European regions, which will help us to better understand the overall diversity and karyotype evolution in these arachnids
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