Ovarian Histology of Two Xo Murid Rodents From Australia

Abstract

Summary. Single XO individuals of Rallu.s liinneyi and Mesemhriomys (Rodentia: Muridae) proved to be phenolypic females. Comparisons of the ovaries of these mdividuals with XX controls revealed that the R nmncyi washistologically nonnal. whereas the M. goiildii was histologicaliy unusual. The results are discussed in relation to the Lyon and Hawker hypothesis which relates fertility of XO mammals to shortness of life-span. INTRODUCTIONIn mammals, the Y-chromosome is male-determining so that XO individuals are phenotypic females. However, in most cases, the XO condition leads to sterility, e.g. humans (Lyon and Hawker, 1973), pig (Nes, 1968. cited in Lyon and Hawker, 1973, horse (Payne, Ellsworth and Degroot, i968;Chandley £^/a/., 1975; Bruere e/a/.. 1978;Blue, Bruere and Dewes, 1978), rhesus monkey (Weiss e/a/., 1973), and the marsupial tammar (Shannan et al., 1970).The XO condition is known to be fertile only in the rodents Mus musculus (Lyon and Hawker. 1973), Akodon azarae (Bianchi and Contreras, 1967), and Microius oregoni (Ohno, 1964). However, XO is the normal female condition in A. azarae and M. oregoni, and in these species probably represents an extension of X-inactivation (Fredga, 1970). Therefore, fertility of XO individuals in these two species can hardly be used to support the general statement that XO rodents are fertile. Ovarian histology of XO Mus musculus indicates that follicles mature and form corpora iutea, but a premature loss of oocytes takes place (Lyon and Hawker, 1973). Other rodent species where an occasional XO individual has been reported are Rattus rattus (Yong, 1971;Prakash and Aswathanarayana. 1977;Yosida, 1977) and the Indian mole rate (Sharma and Raman, 1971). However, the gonads of these XO individuals apparently have not been examined histologicaliy. Thus,

Chromosome evolution in Australian Rattus ? G-banding and hybrid meiosis

“…G-banding showed that these individuals, both of which were female, possessed a full complement of autosomes, but only a single X-chromosome and no Y-chromosome. The G-banded karyotype and ovarian histology of one such individual has been published elsewhere (Baverstock et al, 1980).…”