Karyotype and male meiosis in Spartocera batatas and meiotic behaviour of multiple sex chromosomes in Coreidae (Heteroptera)

María José Franco,María José Bressa,Alba Graciela Papeschi

doi:10.14411/eje.2006.002

Abstract

The Coreidae (Heteroptera) have holokinetic chromosomes and during male meiosis the autosomal bivalents segregate reductionally at anaphase I while the sex chromosomes do so equationally. The modal diploid chromosome number of the family is 2n = 21, with a pair of m-chromosomes and an X0/XX sex chromosome system. A 2n = 24/26 (male/female) and an X1X20/X1X1X2X2 sex chromosome system were found in Spartocera batatas (Fabricius). C-banding and fluorescent-banding revealed the presence of AT-rich heterochromatic bands medially located on all the autosomes, and one telomeric band on both the X1 and X2 chromosomes. This banding pattern differed from the telomeric heterochromatin distribution found in most other heteropteran species. The X1 and X2 chromosomes were intimately associated during male meiosis and difficult to recognize as two separate entities. Based on a comparison with the behaviour of sex chromosomes in other coreids and other heteopterans with multiple sex chromosomes it is suggested that the particular behaviour of X1 and X2 chromosomes in coreid species with multiple sex chromosome systems evolved as an alternative mechanism for ensuring the proper segregation of the sex chromosomes during meiosis.

Highlights

The Coreidae include at least 250 genera and 1800 species, which are distributed worldwide, but are more abundant in the tropics and subtropics
The X1 and X2 chromosomes were very intimately associated from pre-meiotic interphase until telophase II, making their recognition as two different entities difficult
In the first meiotic division, the autosomal bivalents were arranged on the metaphase plate in a ring configuration, with the m pseudo-bivalent located at its center and the X1-X2 chromosomes lying outside the ring (Fig. 2g)

Summary

Introduction

The Coreidae include at least 250 genera and 1800 species, which are distributed worldwide, but are more abundant in the tropics and subtropics. The diploid chromosome number of the family ranges from 13 to 28 with the modal number of 2n = 21, which is present in 47 out of the 106 species cytogenetically analyzed (44.3%) (Fig. 1) (Ueshima, 1979; Manna et al, 1985; Papeschi & Bressa, in press). The Coreidae are characterized by a pair of m-chromosomes, which are found in 80.4% of the species This chromosome pair differs in behaviour from the autosomes and sex chromosomes; i.e., the m-chromosomes are achiasmatic, associate in a pseudobivalent at metaphase I and segregate pre-reductionally at anaphase I (Ueshima 1979; Bressa et al, 2001; Cattani et al, 2004; Cattani & Papeschi, 2004; Bressa et al, 2005). One exception to this meiotic behaviour is described in Coreus marginatus Linnaeus by Nokkala (1986) and Suja et al (2000), who reported that the m-chromosomes were present as a bivalent in some cells. Three species of Acanthocephala Laporte are reported as having an XY/XX system (Wilson, 1907, 1909) and a multiple system of X1X2X30 in males has been ascribed to one population of Coreus marginatus (Xavier, 1945)

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Conclusion