Sex chromosome polymorphism in a species of Belostoma (Belostomatidae, Heteroptera)

• Autores: Papeschi, A.G.
• Año de publicación: 1996
• Idioma: inglés
• Tipo de recurso: artículo
• Fuente: HEREDITAS 1996;124(3):269-274
• Materia: animal cell; article; chromosome polymorphism; chromosome variant; female; Hemiptera; karyotype; male; metaphase chromosome; nonhuman; sex chromosome; species; X chromosome; Y chromosome; Animalia; Belostoma; Belostomatidae; Hemiptera; Heteroptera
• Institución: Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales

A population of Belostoma sp. polymorphic for the sex chromosome determining system has been analyzed. The fundamental karyotype of the species is 2n = 16 = 14 + XY (male), and at different times individuals 2n = 17 have been encountered in a low frequency (27% and 16%, respectively). Sex chromosome area measurements confirm that the original X chromosome of the XY system has fragmented into two unequal-sized chromosomes (X1 and X2). At male metaphase II, the sex univalents associate in a pseudotrivalent that can show different arrangements (in a chain, in a double-plate, or in other transitional arrangements). Their frequency varies among individuals. The present polymorphic population represents a direct evidence of a multiple sex chromosome system originating through fragmentation of the single X. The different kinds of arrangement of the three sex chromosomes at male metaphase II, and their frequency within each individual suggest that some forces are acting to achieve a double plate arrangement and a regular meiotic behaviour. The maintenance of the polymorphism during more than three years seems to indicate that the new chromosomal variant is neutral, or even could be selectively advantageous.
Fil:Papeschi, A.G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.