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Spiders represent one of the most studied arachnid orders. They are particularly intriguing from a cytogenetic point of view, due to their complex and dynamic sex chromosome determination systems. Despite intensive research on this group, cytogenetic data from African spiders are still mostly lacking. In this study, we describe the karyotypes of 38 species of spiders belonging to 16 entelegyne families from South Africa and Namibia. In the majority of analysed families, the observed chromosome numbers and morphology (mainly acrocentric) did not deviate from the family-level cytogenetic characteristics based on material from other continents:   Tetragnathidae   (2n♂ = 24),   Ctenidae   and   Oxyopidae   (2n♂ = 28),   Sparassidae   (2n♂ = 42),   Gnaphosidae  ,   Trachelidae   and   Trochanteriidae   (2n♂ = 22), and   Salticidae   (2n♂ = 28). On the other hand, we identified interspecific variability within   Hersiliidae   (2n♂ = 33 and 35),   Oecobiidae   (2n♂ = 19 and 25),   Selenopidae   (2n♂ = 26 and 29) and   Theridiidae   (2n♂ = 21 and 22). We examined the karyotypes of   Ammoxenidae   and   Gallieniellidae   for the first time. Their diploid counts (2n♂ = 22) correspond to the superfamily   Gnaphosoidea   and support their placement in this lineage. On the other hand, the karyotypes of   Prodidominae   (2n♂ = 28 and 29) contrast with all other   Gnaphosoidea  . Similarly, the unusually high diploid number in    Borboropactus    sp. (2n♂ = 28) within the otherwise cytogenetically uniform family   Thomisidae   (mainly 2n♂ = 21–24) supports molecular data suggesting a basal position of the genus in the family. The implementation of  FISH  methods for visualisation of rDNA clusters facilitated the detection of complex dynamics of numbers of these loci. We identified up to five loci of the 18S rDNA clusters in our samples. Three different sex chromosome systems (X0, X 1 X 2 0 and X 1 X 2 X 3 0) were also detected among the studied taxa.

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