title: Chromosomes of Heterobilharzia americana (Digenea: Schistosomatidae), with ZWA sex determination, from Louisiana.
abstract: Mitotic chromosomes of Heterobilharzia americana from Louisiana are described from parasite material that was dissected from snails, air-dried on slides, and stained with conventional Giemsa and C-band methods. As in other schistosomes, the female is the heterogametic sex. This Louisiana strain, however, differs from a Texas strain and other schistosome species in that the male and female have different diploid numbers of chromosomes (male, 20; female, 19), and the strain has a ZZ male/ZWA female sex-determining mechanism. The chromosomes of the male resemble those of the Texas strain in number and morphology with the Z chromosomes being metacentric and the largest elements in the karyotype. The others form a series decreasing in size to very small number 10's. Chromosomes 2,3, and 4 are subtelocentric; 5 is subtelocentric to acrocentric and is satellited; 6 is submetacentric to subtelocentric; 7 is submetacentric; 8 is subtelocentric to submetacentric; 9 is metacentric to submetacentric; and 10 is metacentric. The female complement differs from the male of this strain in having only 1 normal chromosome 5. The other number 5 and most of the original W apparently have fused tandemly to form the WA chromosome (a "neo-W").
authors: Department of Biological Science, Florida State University, Tallahassee 32306-2043.
authors: R B
authors: RB
authors: Short
authors: W H
authors: WH
authors: Teehan
authors: J D
authors: JD
authors: Liberatos
mesh_terms: D000818:Animals; D002503:Centromere; D002875:Chromosomes / Q000145:classification / Q000648:ultrastructure*; D004171:Diploidy; D005260:Female; D007621:Karyotyping; D008145:Louisiana; D008297:Male; D008938:Mitosis; D012551:Schistosomatidae / Q000235:genetics*; D012730:Sex Chromosomes / Q000145:classification / Q000648:ultrastructure; D012732:Sex Determination Analysis; D012908:Snails; D013781:Texas