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Ultrastructural Observations on the Origin and Differentiation of Somatic Cells during Gonadal Development in the Frog Rana nigromaculata
Author(s) -
TANIMURA AKIHIKO,
IWASAWA HISAAKI
Publication year - 1988
Publication title -
development, growth and differentiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 66
eISSN - 1440-169X
pISSN - 0012-1592
DOI - 10.1111/j.1440-169x.1988.00681.x
Subject(s) - biology , medulla , gonad , medullary cavity , cortex (anatomy) , ovarian cortex , anatomy , sexual differentiation , endocrinology , microbiology and biotechnology , embryo , neuroscience , cryopreservation , biochemistry , gene
The process of gonad development in the frog Rana nigromaculata was observed using the electron microscope. The gonadal medulla was formed by the proliferation and displacement of the epithelial cells within the primordial gonad, and a distinct continuity was observed between the cortical and medullary cells. Sex differentiation of the gonad occurred directly from the sexually indifferent primordial gonads. In the rudimentary testes, the continuity between the cortical and medullary regions increased closer, and the intermingling of cortical and medullary cells was evident. The inner region of the cortex developed into a cord‐like structure and subsequently differentiated into rudimentary seminiferous tubules. The medulla differentiated into the testicular rete and efferent duct. In the rudimentary ovaries, the cortex and medulla were separated and the ovarian cavity was formed in the medullary region. In the cortex, the cortical cells surrounding oocytes which had reached the diplotene stage, differentiated into follicular cells. The intrusion of mesenchymal or blastemal cells derived from extragonadal regions into the cortex or medulla was never observed. These findings do not support Witschi's cortico‐medullary antagonistic theory of sex differentiation.