Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

The Control of the Reptilian Gonad

Ian P. Callard, Stephen W. C. Chan and Marie Anderson Potts
American Zoologist
Vol. 12, No. 2 (May, 1972), pp. 273-287
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/3881616
Page Count: 15
  • Download ($42.00)
  • Subscribe ($19.50)
  • Cite this Item
The Control of the Reptilian Gonad
Preview not available

Abstract

In reptiles, there is adequate evidence to indicate environmental control of the ovarian cycle through hypothalamic pathways and the subsequent release of tropic hormone (s) from the anterior pituitary. The role of the pineal-parietal complex still remains to be elucidated. In the hypothalamus there appear to be steroid sensitive areas, and both progesterone and estrogen appear to have important feedback influences upon gonadal growth, ovulation, and ovarian steroid production. Cytological studies of the reptilian pituitary indicate similar cell types to those observed in mammalian pituitaries, but thus far, two gonadotrophs cannot be identified with any certainty. Chemical and biological studies of the action of mammalian gonadotropins suggest that in reptiles hormones which are FSH-like in mammals are able to stimulate gonadal development, ovulation, and steroid biosynthesis under certain conditions. Preliminary studies of the chemistry of turtle gonadotropins have so far demonstrated only one active principle, which is chemically similar to mammalian LH, but is far more active than the latter hormone in reptilian systems. Further, the hormone also has FSH-like activity in the reptile. Thus, reptilian gonadal development can be stimulated by treatment with a variety of mammalian gonadotropins. Recent studies have indicated an important role for growth hormone, acting in concert with gonadotropin and estrogen in the regulation of vitellogenesis and ovarian growth. Prolactin appears to be an antigonadal agent in reptiles, as does progesterone. The exact manner in which these hormones exert their antigonadal action remains to be clarified, but at least one site of action is the central nervous system; other sites may be the liver and the fat depot. Ovarian tissue from reptiles is able to synthesize and secrete steroid hormones by pathways similar to those present in mammalian ovaries. Circulating levels of estrogen have not been measured, but progesterone levels in the blood show distinct changes associated with pregnancy and the presence of corpora lutea in the ovary.

Page Thumbnails

  • Thumbnail: Page 
273
    273
  • Thumbnail: Page 
274
    274
  • Thumbnail: Page 
275
    275
  • Thumbnail: Page 
276
    276
  • Thumbnail: Page 
277
    277
  • Thumbnail: Page 
278
    278
  • Thumbnail: Page 
279
    279
  • Thumbnail: Page 
280
    280
  • Thumbnail: Page 
281
    281
  • Thumbnail: Page 
282
    282
  • Thumbnail: Page 
283
    283
  • Thumbnail: Page 
284
    284
  • Thumbnail: Page 
285
    285
  • Thumbnail: Page 
286
    286
  • Thumbnail: Page 
287
    287