Pericentric Inversion Polymorphism inAiolopus Strepens(Orthoptera: Acrididae): Effects on Chiasma Formation

Abstract

Seven out of 61 males and five out of 48 females from a Spanish population of Aiolopus strepens were heterozygous for a pericentric inversion in the smallest member of the complement (S₁₁). The inverted segment occupied about 50% of total length of the chromosome which was present either as a telocentric (standard) or a metacentric (inverted) element. Mean chiasma frequency was similar in both standard homozygous and in heterozygous males. However, the pattern of chiasma localization in the three S-bivalent was different in these two types of males. In S₁₁ bivalents heterozygous for the inversion the single chiasma was always terminally located, while in the standard homozygous bivalents the chiasma was sited interstitially in about 30% of diplotene cells. Furthermore, in males heterozygous for the S₁₁-inversion the S₉ and S₁₀ bivalents also show a single terminal chiasma at a higher frequency than that present in males homozygous for the standard S₁₁.