Karyotype and sex chromosome differentiation in two Nalassus species (Coleoptera, Tenebrionidae)

Abstract

Cytogenetic features of Nalassus bozdagus Nabozhenko & Keskin, 2010 and Nalassus plebejus Küster, 1850 were analysed using conventional and differential staining. Mitotic and meiotic chromosomal analysis revealed the diploid number as 2n = 20 (9+Xyp) in both species. Besides the general resemblance of two Nalassus Mulsant, 1854 karyotypes, important differences related to variations in the number of metacentric/submetacentric chromosomes, localization of highly impregnated regions which are considered as NOR and heterochromatin distribution are clearly observed. The most prominent difference between two species is found related to the X chromosome which is clearly larger in Nalassus bozdagus and has a conspicuous secondary constriction on the long arm. As a result of silver staining, the existence of highly impregnated areas associated with Xyp of Nalassus bozdagus in both prophase I and metaphase I, suggests that NORs are seemingly located on sex chromosomes. On the other hand, the potential NORs of Nalassus plebejus were observed only in prophase I nuclei. With the application of fluorescence dye DAPI, the AT rich chromosome regions and Xyp which forms the parachute configuration were shown in both species.

A New Record of Reduced Chromosome Number in Tenebrionidae (Coleoptera)

“…The heterochromatin in Coleoptera can be detected on pericentromeric regions (Rozek, 1998;Pons et al, 2004;Bione et al, 2005;Lachowska et al, 2005;Şendoğan & Alpagut Keskin, 2016, Çalışan & Alpagut-Keskin, 2023 as well as on telomeric regions (Bione et al, 2005;Colomba et al, 2006;Dutrillaux & Dutrillaux, 2009;Şendoğan et al, 2019). In A. subtricostata pericentromeric blocks were demonstrated with silver nitrate and Giemsa staining.…”