n Sitogenetiese ondersoek van Suider-Afrikaanse korthoringsprinkane

Abstract

A cytogenetic survey was carried out on a number of Southern African short horned grasshopper species (OR.TBOPTKR.A), the aim being to expand the existing limited information. New methods of analysis were developed, while existing methods were improved. 438 individuals of 116 species (7 families) were studied. Surprisingly many cytogenetic variations were found. To simplify the analysis, a bivalent type analysis was done. From this analysis mean chiasma frequencies and chiasma localization could be determined. To simplify comparisons between species, the bivalent types are presented in the form of histograms. The male zygotic chromosome numbers of the following families are: ACRIDIDAK, CBAR.ILAIDAK, Lentulidae and LKNTULIDAK 2n6"=23(XO); PAIIPBAGIDAE and PYR.GOIIOIPBIDAK 2n~l 9(XO); KUIIASTACIDAK 2n~l 7(XO). Their karyotypes consist mostly of acrocentric chromosomes. Pericentric inversion polymorphisms were found in 3 ACRIDIDAK species. One Lentulidae species is polytypic for centric fusion translocations. Supernumerary heterochromatin is present in the form of autosomal segments and B-chromosomes. The segments were found in 13 species being most prevalent in the genera 0edaleus and Acrotylus. They are found in the smaller bivalents in either the homozygotic of heterozygotic state. They are located in the chromosomes as follows: distal (67,70%), proximal (12,12%), interstitial (9,09%) and extrinsic (9,09%). B chromosomes were found only in 8 species appearing in two sizes; small (smaller than the smallest chromosome) and large (three quarters the size of the X-chromosome). Chiasma localization and/or lowered chiasma frequency occurred in 7 ACR.IDIDAE species. The frequency is limited in some species, as is the position to the proximal or distal regions of the bivalents. In there’s the chiasmata restricted to the proximal and distal parts of the bivalents without having any inf1uence on the chiasma, frequency. Crossing over in the short arm is particularly rare, but overall relatively frequent in 8 genera. It is clear that a fair amount of cytogenetic variation exists in Southern African short horned grasshoppers. A few species groups could be identified, warranting further study.