Chiasma Frequency and Distribution in Males and Females of Metaleptea Bremcomis Adspersa (Acridinae, Acrididae) with and without B. Chromosomes

摘要

Previous studies on the South American grasshopper Metaleptea brevicomis adspersa revealed the existence of a widespread polymorphism for a large B chromosome with isochromosome characteristics. In this work, we analyse the frequency and distribution of chiasmata in OB and IB males and females belonging to two populations in Misiones province (Argentina), from the localities of Wanda and Eldorado. The comparative analysis of meiosis in both sexes revealed significant differences between OB males and females, the latter having significantly lower chiasma frequencies. Chiasma distribution is also significantly different. M. b. adspersa is thus a new example of “two-track heredity” where the homogametic and not the heterogametic sex is the one that shows limited recombination. The B chromosome present in both populations tends to increase chiasma frequency slightly in both sexes.