Possible autosomal origin of macro B chromosomes in two grasshopper species.
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.
Loreto
Vilma
V
Unidade Acadêmica de Garanhuns, Universidade Federal Rural de Pernambuco, Recife, PE, Brazil. vloreto@bol.com.br
Cabrero
Josefa
J
López-León
Maria Dolores
MD
Camacho
Juan Pedro M
JP
Souza
Maria José
MJ
D000818:Animals; D002875:Chromosomes / Q000737:chemistry / Q000502:physiology*; D005260:Female; D049810:Genetic Speciation; D006110:Grasshoppers / Q000235:genetics*; D007621:Karyotyping; D008297:Male