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In addition to the principal B chromosome (B1) in Moroccan populations of the grasshopper Eyprepocnemis plorans, nine B chromosome variants appeared at low frequency. The transmission of five of these rare B chromosome variants through females was analysed in three natural populations. Sixteen controlled crosses provided useful information on the transmission of BM2, BM6 and BM7 in Smir, BM3 and BM6 in SO.DE.A. (Société de Développement Agricole lands near Ksar-el-Kebir city), and BM2 and BM10 in Mechra, all located in Morocco. Since six female parents carried two different B variants, a total of 22 progeny analyses could be studied. Intraindividual variation in B transmission rate (kB) was observed among the successive egg pods in 26.7 % of the females, but this variation did not show a consistent temporal pattern. Only the BM2 and BM6 variants in Smir showed net drive, although variation was high among crosses, especially for BM2. These two variants are thus good candidates for future regenerations (the replacement of a neutralized B, B1 in this case, by a new driving variant, BM2 or BM6) in Smir, the northern population where the B polymorphism is presumably older. The analysis of all crosses performed in the three populations, including those reported previously for the analysis of B1 transmission, showed that the largest variance in kB among crosses stands at the individual level, and not at population or type of B levels. The implications of these findings for the occurrence of possible regeneration processes in Moroccan populations are discussed. Copyright © 2004 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

The persistence of parasitic B chromosomes in natural populations depends on both B ability to drive and host response to counteracting it. In the grasshopper Eyprepocnemis plorans, the B24 chromosome is the most widespread B chromosome variant in the Torrox area (Málaga, Spain). Its evolutionary success, replacing its ancestral neutralized B variant, B2, was based on meiotic drive in females, as we showed in a sample caught in 1992. In females collected six years later, mean B24 transmission ratio (kB) was 0.523, implying a very rapid decrease from the 0.696 observed in 1992. This shows that B24 neutralization is running very fast and suggests that it might most likely be based on a single gene of major effect. Copyright © 2004 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

B chromosome variation in nine Moroccan populations of the grasshopper Eyprepocnemis plorans was analysed for 3 consecutive years. In addition to B1, which was the predominant B chromosome in all nine populations, we found 15 other B variants, albeit at very low frequency. Eight variants were found in adults caught in the wild, four appeared in adults reared in the laboratory and seven were found in embryo progeny of controlled crosses between a 0B male and a B-carrying female. Some variants were found in more than one kind of material. At least the seven B variants that appeared in embryo progeny of females carrying a different B type arose de novo through mutation of the maternal B chromosome. The mutation rate of B chromosomes was 0.73%, on average, which explains the high variety of morphs and banding patterns found. The most frequent de novo mutations observed in these chromosomes were centromere misdivision with or without chromatid nondisjunction, which generates iso-B-chromosomes or telocentric Bs, respectively, as well as transtocations with A and B chromosomes and deletions. But the whole variation observed, including that found in adult individuals, suggests that other mutations such as duplications, inversions and centric fusions do usually affect B chromosomes. Finally, B chromosome mutation rate was remarkably similar in both Moroccan and Spanish populations, which suggests that it might be dependent on B chromosome intrinsic factors. [ABSTRACT FROM AUTHOR]

Analysis of chromosome localization of three molecular markers, 18S-5.8S-28S rDNA, 5S rDNA and a 180 bp satDNA, showed that B chromosomes in the grasshopper Eyprepocnemis plorans originated independently in Eastern (Caucasus) and Western (Spain and Morocco) populations. Eastern B chromosomes are most likely derived from the smallest autosome, which is the only A chromosome carrying the three markers, in coincidence with Caucasian B chromosomes. Western B chromosomes, however, lack 5S rDNA and are most likely derived from the X chromosome, which is the only A chromosome carrying the two remaining markers, always in the same order with respect to the centromere, as the B chromosome. [ABSTRACT FROM AUTHOR]

Examines the transmission of the B[sub1] chromosome through females of Moroccan populations of the grasshopper Eyprepocnemis plorans. Assessment of the transition ratio variation; Performance of intra- individual and inter-individual test; Difference in K[subB] values among egg-pods.