Cytogenetic analysis of Australian tiger beetles (Coleoptera : Cicindelidae): chromosome number, sex-determining system and localization of rDNA genes

The chromosomes of four species of Australian tiger beetle are documented. The male meioformulae of three species of Cincindela (tribe Cicindelini) we re determined as follow: Cicindela cardinalba Sumlin 1987. n = 10 + X-1 X-2 X3Y; C. sp. (saetigera group) and Cicindela gillesensis Hudson 1994, n = 1 1 + X1X2X3Y. The male meioformula of Megacephala whelani Sumlin 1992 (tribe Megacephalini) is n = 12 + XY. Fluorescence in situ hybridization (FISH) w as used to localize the 18S-28S ribosomal gene clusters on male mitotic and meiotic chromosomes and nuclei using a polymerase chain reaction-amplified ribosomal probe. Fluorescence in mitosis and meiotic first prophase stages in the three Cicindela species showed that rDNA genes are in two of the fo ur chromosomes that form the sex vesicle. In M. Whelani hybridization in mi tosis and first metaphase stages indicate that rDNA genes are in three, med ium- to small-sized. autosomal pairs. Silver staining of male meiotic nucle i reveals the presence of active nucleolar organizing regions (NORs) in the sex vesicle of the three species of Cicindela. The cytogenetic and evoluti onary implications of these findings are discussed.