INTRODUCTION The Coreidae include at least 250 genera and 1800 spe- cies, which are distributed worldwide, but are more abun- dant in the tropics and subtropics. Coreids are all phy- tophagous; most species feed on the vascular systems of plants and some are of economic importance (Schuh & Slater, 1995). Spartocera batatas (Fabricius) (subfamily Coreinae, tribe Spartocerini) causes damage to sweet potato Ipomoea batatas (Linnaeus) in Puerto Rico and Jamaica, and is also encountered in Brazil and Argentina (Schaefer & Panizzi, 2000). From a cytogenetic point of view, the Coreidae possess holokinetic chromosomes and the males show a pre- reductional type of meiosis for the autosomes and post- reductional for the sex chromosomes. Autosomal bivalents with terminal chiasmata segregate reductionally at anaphase I and divide equationally at anaphase II, while the sex chromosomes divide into chromatids during the first meiotic division and segregate reductionally in the second. 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 cyto- genetically analyzed (44.3%) (Fig. 1) (Ueshima, 1979; Manna et al., 1985; Papeschi & Bressa, in press). The Coreidae are also 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 pseudo- bivalent 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). However, 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. The most common sex chromosome system of the family is X0/XX (male/female) (63.3%) followed by the multiple system X1X20/X1X1X2X2 (32.7%) (Ueshima, 1979; Pape- schi et al., 2003, Cattani et al., 2004; Cattani & Papeschi, 2004; Bressa et al., 2005). Three species of Acantho- cephala 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). Most reports on C-positive heterochromatin distribution in Heteroptera describe the C-bands as terminally located, but in a few species interstitial blocks have been observed (Camacho et al., 1985; Panzera et al., 1995; Grozeva & Nokkala, 2001; Grozeva et al., 2004; Ituarte & Papeschi, 2004; Bressa et al., 2005). Heterochromatin characteriza- tion has shown that C-bands are generally DAPI bright and CMA dull, and in the few species, in which CMA bright bands were detected they correspond to nucleolus organizing regions (González-García et al., 1996; Pape- schi & Bressa, 2002; Papeschi et al., 2003; Rebagliati et al., 2003; Cattani & Papeschi, 2004). A previous report on species belonging to the tribe Spartocerini refer to Spartocera fusca (Thunberg), a spe- cies with a diploid number 2n = 20 + 2m + X0/ XX (male/female) (Cattani & Papeschi, 2004). In the present Eur. J. Entomol. 103: 9–16, 2006 ISSN 1210-5759 Karyotype and male meiosis in Spartocera batatas and meiotic behaviour of multiple sex chromosomes in Coreidae (Heteroptera) MARÍA JOSÉ FRANCO 1 , MARÍA JOSÉ BRESSA 1, 2 and ALBA GRACIELA PAPESCHI 1, 2 * 1 Laboratorio de Citogenética y Evolución, Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina; e-mail: alpape@ege.fcen.uba.ar 2 Members of the Carrera del Investigador Científico (CONICET) Keywords. Holokinetic chromosomes, multiple sex chromosomes, C-banding, fluorescent-banding, karyotype evolution, Heteroptera 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 heterop- teran 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 chromo- some systems evolved as an alternative mechanism for ensuring the proper segregation of the sex chromosomes during meiosis. 9 * Corresponding author.