- INVITED REVIEW - Evolutionary cytogenetics in Heteroptera ALBA GRACIELA PAPESCHI* and MARIÁ JOSÉ BRESSA Laboratorio de Citogenética y Evolución, Departamento de Ecologèa, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina Abstract In this review, the principal mechanisms of karyotype evolution in bugs (Heteroptera) are discussed. Bugs possess holokinetic chromosomes, i.e. chromosomes without primary constriction, the centromere; a pre-reductional type of meiosis for autosomes and m-chromosomes, i.e. they segregate reductionally at meiosis I; and an equational division of sex chromosomes at anaphase I. Diploid numbers range from 2n=4 to 2n=80, but about 70% of the species have 12 to 34 chromosomes. The chromosome mechanism of sex determination is of the XY/XX type (males/females), but derived variants such as an X0/XX system or multiple sex chromosome systems are common. On the other hand, neo-sex chromosomes are rare. Our results in heteropteran species belonging to different families let us exemplify some of the principal chromosome changes that usually take place during the evolution of species: autosomal fusions, fusions between autosomes and sex chromosomes, fragmentation of sex chromosomes, and variation in heterochromatin content. Other chromosome rearrangements, such as translocations or inversions are almost absent. Molecular cytogenetic techniques, recently employed in bugs, represent promising tools to further clarify the mechanisms of karyotype evolution in Heteroptera.   < back .