Anatomy and chromosomes of two intersexual dasyurid marsupials
P. A. Woolley A D , N. Guedelha B E and J. A. M. Graves B CA Department of Zoology, La Trobe University Bundoora, Vic. 3086, Australia.
B Department of Genetics, La Trobe University Bundoora, Vic. 3086, Australia.
C Present address: Research School of Biological Sciences, The Australian National University, Canberra, ACT 2601, Australia.
D To whom correspondence should be addressed. email: p.woolley@latrobe.edu.au
E *N. Guedelha’s contribution to this paper was the investigation of the Sminthopsis douglasi karyotypes.
Reproduction, Fertility and Development 15(5) 293-301 https://doi.org/10.1071/RD03045
Submitted: 4 July 2003 Accepted: 2 September 2003 Published: 2 September 2003
Abstract
The intersexual phenotypes of marsupials with XXY and XO chromosome constitutions imply that not all sexual dimorphisms are under the control of testicular hormones and, ultimately, the SRY gene on the Y chromosome. It has been hypothesised that there is a gene on the X chromosome that determines whether either a scrotum will form (one copy of the gene) or a pouch with teats (two copies of the gene). Here, we describe the anatomy and chromosomes of two intersexual dasyurid marsupials. One, a Dasyuroides byrnei, had a pouch, but the reproductive tract was essentially male. The other, a Sminthopsis douglasi, had a hemipouch and a hemiscrotum and the reproductive tract was essentially female. The S. douglasi was a mosaic for cells with an apparently normal 2n = 14, XX female karyotype and cells with 2n = 14 plus (usually) two dot-like supernumerary elements 2n = 14, XX + 2B. The D. byrnei cells examined also had a 2n = 14, XX + 2B karyotype. In fibroblasts from the male and female sides of the S. douglasi, it was possible to assign the 2n = 14, XX karyotype to the male side and the 2n = 14, XX + 2B to the female side.
Extra keywords: chromosome abnormalities, pouch/scrotum differentiation.
Acknowledgments
This work was performed with financial support from La Trobe University, the Living Together Foundation (to P.A.W.) and the Australian Research Council (to J.A.M.G.) and with La Trobe University Animal Ethics Committee approval (no. LSB96/4/V3). We thank Harold Attwood for provision of photographs of the chromosomes of the intersexual D. byrnei, Michael Westerman for the photograph of the chromosomes of the normal male D. byrnei, Iole Barbieri for S. douglasi cell culture, Frank Gruetzner for help with imaging of S. douglasi chromosomes, Alan Wright for photomicrography and Trevor Phillips for preparation of the illustrations.
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