title: Cytosystematics of five North American Dermacentor (Acari: Ixodidae) species.
abstract: The karyotypes of five species of Dermacentor ticks found in North America were examined for the presence and location of constitutive heterochromatin (C-bands) and the location of the nucleolar organizing regions (NORs). All specimens examined had 20 autosomes and an XX:XO sex-determining system; the X was the largest element in the karyotype. Except as noted, the autosomes of all species were acrocentric, and heterochromatin was restricted to the centromeric region. The one-host species D. nitens and D. albipictus were distinguished from the three-host species by a lack of additional bands of heterochromatin and by having a subtelocentric X chromosome. However, some individuals of D. albipictus were observed to have acrocentric X chromosomes. D. nitens differed from D. albipictus in having two subtelocentric autosomal pairs (pairs 1 and 8). A single pair of NORs was noted for the one-host species; however, heterochromatin was not associated with the NORs. Among the three-host species, D. occidentalis showed a band of heterochromatin proximal to the centromere in autosomal pairs 1 and 8, and D. andersoni had similar bands in autosomal pairs 1, 3, 7, and 9. D. variabilis displayed heterochromatic bands in autosomal pairs 3, 7, and 9. All three-host species displayed a single pair of NORs, which was associated with the band of heterochromatin on pair 9. Indications of some genetic incompatibility between the two recognized forms of D. albipictus are discussed.
authors.affiliation: Knipling-Bushland U.S. Livestock Insects Laboratory, USDA-ARS, Kerrville, Texas 78029.
authors.forename: S J
authors.initials: SJ
authors.lastname: Gunn
authors.forename: L R
authors.initials: LR
authors.lastname: Hilburn
mesh_terms: D000818:Animals; D001096:Arachnid Vectors / Q000235:genetics*; D002871:Chromosome Banding; D003870:Dermacentor / Q000235:genetics*; D005260:Female; D006570:Heterochromatin / Q000032:analysis; D007621:Karyotyping; D008297:Male; D013045:Species Specificity; D013987:Ticks / Q000235:genetics*; D014960:X Chromosome
chemical_list: D006570:Heterochromatin