Kinetic activity of the sex chromosomes of Mormidea paupercula (Heteroptera: Pentatomidae)

Pablo Javier Rebagliati,Liliana María Mola

doi:10.14411/eje.2010.040

Abstract

In Mormidea paupercula (n = 6 + XY in males), the presence of a CMA3-bright band in the telomeric regions on both sex chromosomes allowed the analysis of the kinetic activity of the sex univalents and XY pseudobivalent at the first and second meiotic divisions, respectively. The separation of the sister chromatids of the sex chromosomes occurs from a pair of telomeric regions (with or without a band), with opposite telomeric regions remaining associated with each other at meiosis I; the behaviour of both sex chromosomes differs, on the X chromosome both telomeric regions are similarly active, while on the Y chromosome the telomeric region without a band is more frequently active. At the second division, the most frequent associations in the pseudobivalent occur between the telomeric regions of both sex chromosomes with bands or without bands. Therefore, in both meiotic divisions, the same telomeric region on the sex chromosomes could lead the migration, in contrast to that observed usually in autosomal bivalents. These results provide evidence that the sex chromosomes of Heteroptera show more than one pattern of attachment to the spindle.

Highlights

A distinctive trait of the suborder Heteroptera is the presence of holokinetic chromosomes, i.e., with nonlocalised centromeres, as opposed to monocentric chromosomes, which are found in most organisms (Ueshima, 1979)
At metaphase I, the autosomal bivalents are arranged in a ring-shaped figure in the equatorial plane, while the sex chromosomes are usually part of the ring or the Y chromosome lies at its centre (Fig. 1b, e–h)
The selection of the kinetically active telomeric region is independent between sister chromatids of the X chromosome in Graphosoma italicum and Triatoma infestans

Summary

Introduction

A distinctive trait of the suborder Heteroptera is the presence of holokinetic chromosomes, i.e., with nonlocalised centromeres, as opposed to monocentric chromosomes, which are found in most organisms (Ueshima, 1979). The autosomes and sex chromosomes of most Heteroptera exhibit different types of meiosis; the autosomal bivalents usually have a terminal chiasma, are oriented with their long axes parallel to the polar axis at metaphase I, and divide reductionally at the first meiotic division and equationally at the second division. The sex chromosomes are achiasmatic, behave as univalents and divide equationally at the first meiotic division, while the X and Y chromosomes show the so-called touch-and-go pairing at the second meiotic division, forming a pseudobivalent, which divides reductionally (Ueshima, 1979)

Methods

Results

Conclusion