Karyotype evolution in Reduviidae (Insecta: Heteroptera) with special reference to Stenopodainae and Harpactorinae

Heteropteran insects are characterized by holokinetic chromosomes, and, in most species, the post-reductional meiotic division of sex chromosomes and the presence of one chiasma per bivalent. The Reduviidae have a modal diploid autosomal number of 20 with a range between 12 to 34, and both simple and multiple sex chromosome systems (XY/XX, X0/XX, XnY/XnXn). Within this family cytogenetic reports on 127 species belonging to 11 subfamilies are available. Stenopodainae (10 species) have a diploid autosomal number of 20/22 plus different multiple sex chromosome systems; in Harpactorinae 33 species belonging to 18 genera have been cytogenetically analysed, and the modal diploid number of the subfamily is 2n=28=24+X1X2X3Y (male). In the present work we analyse the karyotype and male meiosis of Stenopoda cinerea Laporte, 1833 (2n=25=20+X1X2X3X4Y) (male) (Stenopodainae); Zelus sp. prope leucogrammus (Perty, 1834) (2n=26=24+XY) (male), Apiomerus lanipes (Fabricius, 1803) (2n=24=22+XY) (male), Cosmoclopius nigroannulatus (Stål, 1860) and C. poecilus (Herrich-Schaeffer, 1848) (2n=28/30=24+X1X2X3Y/24+X1X1X2X2X3X3) (male/female) (Harpactorinae). Considering the cytogenetic characteristics of Reduviidae two evolutionary trends can be observed within the family: a reduction in the number of autosomes through fusion mechanisms, and an increase in the number of sex chromosomes through fragmentations (multiple systems). Furthermore, the presence of multiple sex chromosome systems is much more frequent in Harpactorinae and Stenopodainae than in the other subfamilies. These cytogenetic trends support a previously proposed phylogeny based on morphological, ecological and behavioural traits (Ambrose, 1999).