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

Keywords

• holokinetic chromosomes
• multiple sex chromosomes
• c-banding
• fluorescent-banding
• karyotype evolution
• heteroptera