Loreto Vilma, Cabrero Josefa, López-León Maria Dolores, Camacho Juan Pedro M, Souza Maria José
Unidade Acadêmica de Garanhuns, Universidade Federal Rural de Pernambuco, Recife, PE, Brazil.
Chromosome Res. 2008;16(2):233-41. doi: 10.1007/s10577-007-1188-0. Epub 2007 Dec 21.
The acrocentric macro B chromosomes of Rhammatocerus brasiliensis (Acrididae, Gomphocerinae) and Xyleus discoideus angulatus (Romaleidae, Romaleinae) are highly similar to the X chromosome in each species in terms of morphology, size, and pycnosis. However, the results of FISH experiments using 45S and 5S rDNA probes suggest that in both species the B chromosomes are most likely of autosomal origin. In R. brasiliensis, the B chromosome presented 5S rDNA but not 45S rDNA, in resemblance to the L(2), L(3), M(5) and S(11) autosomes, but the X chromosome lacks both rDNA families. In X. d. angulatus, 45S rDNAs is absent from the B chromosome, whereas the X chromosome contains one of the two 45S rDNA clusters in the genome. The occurrence of B chromosomes in all nine R. brasiliensis populations analyzed indicates that they are widely distributed in Northeastern Brazil, and the small amount of interpopulation variation found for B chromosome prevalence suggests the existence of high gene flow, presumably due to the abundance of this grasshopper species on several types of vegetation and its relatively high flight capability.
巴西角蝗（蝗科， gomphocerinae亚科）和盘状突角蝗（瘤蝗科，瘤蝗亚科）的近端着丝粒大B染色体在形态、大小和固缩方面与每个物种的X染色体高度相似。然而，使用45S和5S rDNA探针进行的荧光原位杂交实验结果表明，在这两个物种中，B染色体很可能起源于常染色体。在巴西角蝗中，B染色体呈现5S rDNA，但不呈现45S rDNA，这与L(2)、L(3)、M(5)和S(11)常染色体相似，但X染色体缺乏这两个rDNA家族。在盘状突角蝗中，B染色体不存在45S rDNA，而X染色体包含基因组中两个45S rDNA簇之一。对所有九个巴西角蝗种群的分析表明，B染色体广泛分布于巴西东北部，并且发现B染色体流行率的种群间差异较小，这表明存在高基因流，可能是由于这种蝗虫在几种植被上数量丰富以及其相对较高的飞行能力。
