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

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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.