Chromosoma

, Volume 84, Issue 3, pp 413–430

Karyotype evolution and sex chromosome differentiation in schistosomes (Trematoda, Schistosomatidae)

  • Abraham I. Grossman
  • Robert B. Short
  • George D. Cain
Article

DOI: 10.1007/BF00286030

Cite this article as:
Grossman, A.I., Short, R.B. & Cain, G.D. Chromosoma (1981) 84: 413. doi:10.1007/BF00286030

Abstract

The morphology of C-banded metaphase chromosomes has been studied in two hermaphroditic and ten gonochoristic digenetic trematodes (schistosomes). Comparison of numbers and morphology of chromosomes indicates that the karyotype of primitive trematodes probably was composed of 10 (or 11) pairs of telocentric or subtelocentrie chromosomes, and reduction of chromosome numbers in advanced species resulted from centromeric fusion rather than elimination of chromosomes. Observation of heteromorphic chromosomes in a hermaphroditic trematode (Spirorchis) suggested a differentiation of “pre-sex” chromosomes in species ancestral to dioecious trematodes which possess distinctly differentiated sex chromosomes. Our results indicate that differentiation of Z and W chromosomes in the gonochoristic trematodes resulted from: (a) partial constitutive heterochromatinization of the W chromosome (Schistosoma mansoni and S. haematobium complexes, African schistosomes), (b) deletion of part of the W (S. japonicum and S. mekongi, Asian schistosomes), and (c) translocation of part of one sex chromosome onto another (Schistosomatium douthitti and Heterobilharzia americana, American schistosomes) with subsequent heterochromatinization of the W in H. americana.

Copyright information

© Springer-Verlag 1981

Authors and Affiliations

  • Abraham I. Grossman
    • 1
  • Robert B. Short
    • 1
  • George D. Cain
    • 2
  1. 1.Department of Biological ScienceFlorida State UniversityTallahasseeUSA
  2. 2.Department of ZoologyUniversity of IowaIowa CityUSA
  3. 3.Department of Human Genetics, School of MedicineUniversity of PennsylvaniaPhiladelphiaUSA