Abstract
In the present work, we analysed the male meiosis, the content and distribution of heterochromatin and the number and location of nucleolus organizing regions in Microtomus lunifer (Berg, 1900) by means of standard technique, C- and fluorescent bandings, and fluorescent in situ hybridization with an 18S rDNA probe. This species is the second one cytogenetically analysed within the Hammacerinae. Its male diploid chromosome number is 31 (2n=28+X1X2Y), including a minute pair of m-chromosomes. The diploid autosomal number and the presence of m-chromosomes are similar to those reported in Microtomus conspicillaris (Drury, 1782) (2n=28+XY). However, Microtomus lunifer has a multiple sex chromosome system X1X2Y (male) that could have originated by fragmentation of the ancestral X chromosome. Taking into account that Microtomus conspicillaris and Microtomus lunifer are the only two species within Reduviidae that possess m-chromosomes, the presence of this pair could be a synapomorphy for the species of this genus. C- and fluorescent bandings showed that the amount of heterochromatin in Microtomus lunifer was small, and only a small CMA3 bright band was observed in the largest autosomal pair at one terminal region. FISH with the 18S rDNA probe demonstrated that ribosomal genes were terminally placed on the largest autosomal pair. Our present results led us to propose that the location of rDNA genes could be associated with variants of the sex chromosome systems in relation with a kind of the sex chromosome systems within this family. Furthermore, the terminal location of NOR in the largest autosomal pair allowed us to use it as a chromosome marker and, thus, to infer that the kinetic activity of both ends is not a random process, and there is an inversion of this activity.
Highlights
Reduviidae is the largest family of predaceous land Hemiptera and includes about 6500 species and subspecies in 930 genera and 22 subfamilies
C- and fluorescent bandings showed that the amount of heterochromatin in M. lunifer was small, and only a small chromomycin A3 (CMA3) bright band was observed in the largest autosomal pair at one terminal region
Within Hammacerinae, Microtomus lunifer constitutes the second species cytogenetically analysed, and its diploid autosomal number and the presence of a minute pair of autosomes agree with the previous report in M. conspicillaris (2n=30=28+XY/XX) (Piza 1957)
Summary
Reduviidae is the largest family of predaceous land Hemiptera and includes about 6500 species and subspecies in 930 genera and 22 subfamilies. All hemipteran species possess holokinetic chromosomes, i.e. chromosomes without primary constrictions and, without localized centromeres This order is unique in that the autosomes, m-chromosomes and sex chromosomes have different meiotic behaviours. Several reports provide evidence that kinetic activity during meiosis is restricted to the chromosome ends where no kinetochore structures are observed, and the chromosomes can be regarded as telokinetic (Motzko and Ruthmann 1984) Both chromosome ends can show kinetic activity in such a way that the chromosome end which was inactive at the first meiotic division become active during the second one (Camacho et al 1985, Nokkala 1985, Pérez et al 1997, Cattani et al 2004, Viera et al 2009)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
