The chromosome system in three species of the genusArcypteraII. Unstable B-chromosomes inA. fusca(Pall.)
✍ Scribed by C. López-Fernández; J. Gosálvez
- Publisher
- Springer Netherlands
- Year
- 1983
- Tongue
- English
- Weight
- 666 KB
- Volume
- 62
- Category
- Article
- ISSN
- 0016-6707
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✦ Synopsis
Different populations of the grasshopper Arcypterafusca located through a small valley of the Pyrenees present an unstable B-chromosome system. Frequencies of individuals carrying Bs ranged from 11% to 50%. In the testes of these males the number of Bs varied among the different follicles ranging from 0 to 4 with 2 being the number most commonly found. The variation in the number of supernumeraries probably resulted from their preferential non-disjunction in the earl3; mitosis prior to the differentiation of the follicles.
The meiotic behaviour of Bs depends on their number within each follicle. When two or more Bs are present they usually pair and segregate regularly; B univalents divide in anaphase I and segregate without further division in anaphase II in 75% of the cells observed.
The presence of Bs does not affect the chiasma frequency, however, the males with Bs had fewer follicles in their testes; this event could be related with the non-existence of follicles with more than 4 Bs.