Regularities and restrictions governing C-band variation in acridoid grasshoppers

New hypotheses about the origin of supernumerary chromosome segments in grasshoppers

“…On the one hand, the paracentromeric C-bands are absent from some chromosomes of Ch.vagans and Ch.brunneus. Because the presence of paracentromeric C-bands is the norm in gomphocerine chromosomes (Cabrero and Camacho, 1986a) and given that there is no change in morphology or size of these chromosomes (as would be expected in the case of a deletion), we propose that these paracentromeric C-bands have been lost by means of a process of transformation of heterochromatin into euchromatin, similarly to that reported for the paracentromeric C-bands in the neo-Y chromosome of the grasshopper Slenacatantops angustifrons (King and John, 1980). On the other hand, the existence of euchromatic extra segments in the M6 chromosomes of Chorthippus binotatus (this paper) and Omocestus bolivari (Camacho et a!., 1984) contradicts all the existing hypotheses for the origin of extra segments.…”

Karyotype characterization of planthopper species Hysteropterum albaceticum Dlabola, 1983 and Agalmatium bilobum (Fieber, 1877) (Homoptera: Auchenorrhyncha: Issidae) using AgNOR-, C- and DAPI/CMA3 -banding techniques

“…The species can diverge considerably in this pattern: some display a lot of C-heterochromatin; some show prominent C-bands of different size in separate chromosomes; and in other species C-heterochromatin appeared to avoid detection due to its presence in small or minute amounts. Actually, this happens also with monocentric groups, in which some species are known to have a large amount of C-heterochromatin but some species not (King, John, 1980;Hoshiba, Imai, 1993;Graphodatsky, Fokin, 1993;Swarça et al, 2003;Rozek et al, 2004). This allows suggestion that holokinetic chromosomes in fact differ slightly or not at all in constitutive heterochromatin amount from monocentric chromosomes.…”

Equilocality and heterogeneity of constitutive heterochromatin: in situ localization of two families of highly repetitive DNA in Dociostaurus genei (Orthoptera)

“…These usually correspond to regions of constitutive heterochromatin that are revealed by C-banding (John, 1988). Other banding methods prove that these sequences are homogenized when they occupy identical chromosome distribution within a given complement (equilocality) and are different in distinct chromosome domains (heterogeneity) (King & John, 1980;Greilhuber & Loidl, 1983;Schweizer et aL, 1983;Bella et al, 1986).…”