CYTOGENETIC STUDY IN SAND SPIDERS (SICARIIDAE) FROM THE BRAZILIAN CAATINGA: SEX CHROMOSOME SYSTEM DIVERSITY IN CLOSELY RELATED SPECIES

In this study, we investigated the chromosomes of three species Sicarius spiders from Brazilian Caatinga, using classical and molecular cytogenetic techniques. Based on phylogenetic approach, also discussed about variation diploid number, types sex chromosome system changes in localization ribosomal genes Scytodoidea. are Synspermiata that together with genera Loxosceles Hexophthalma constitute family Sicariidae. group, available data showed a low number range (2n♂=18 to 2n♂=23) presence only multiple systems (X1X2Y X1X20). Mitotic metaphase cells exhibited 2n♂=16+X1X2Y for cariri S. ornatus, 2n♂=18+XY tropicus. these species, silver impregnation revealed nucleolar organizer region (Ag-NOR) terminal pair 1. ornatus tropicus, results obtained fluorescent situ hybridization (FISH) 18S rDNA probe were similar Ag-NOR, however cariri, sites localized X1 chromosome. work, presented first description simple Sicariidae, helping understand how XY evolved X1X2Y system. Additionally, FISH incongruous Ag-NOR indicate studies Sicariidae allow investigating relation between karyotype evolution distribution activity genes. Key words: karyotype, mitosis, region, rDNA,