TitleThe influence of sex steroids on the sexual size dimorphism in the red-spotted garter snake, Thamnophis sirtalis concinnus
Publication TypeJournal Article
Year of Publication2001
AuthorsLerner, DT, Mason, RT
JournalGeneral and Comparative Endocrinology
Volume124
Pagination218-225
Type of ArticleJournal Article
ISSN0016-6480
Abstract

The red-spotted garter snake exhibits adult size dimorphism in which females are the larger sex. To understand which hormones may influence differential growth in this species, growth curves and hormone profiles of estradiol-17 beta (E-2) and testosterone (T) were constructed in male and female neonates. Growth was manipulated via implantation of exogenous hormones and hormone antagonists. Female neonates are heavier or longer beginning at either 20 or 24 weeks of age, respectively. Although low circulating levels of E-2 and T were present in males and females from birth through 15 weeks of age, these levels were not significantly different between the sexes. Differences in the growth curves of the treated and untreated snakes were significant after 24 weeks of age. Antiestrogen produced male-like growth in females but had no effect on males. Antiandrogen had no effect on either males or females. Exogenous T reduced female growth to that observed in males, and E-2 reduced male growth. These results suggest that a basal level of either E-2 or T is sufficient in males to retain typical male growth patterns. Similar endogenous levels of E-2 appear to have growth-promoting effects in females. Endogenous T does not appear to play a role in female growth. (C) 2001 Academic Press.

URL<Go to ISI>://WOS:000172078100009
DOI10.1006/gcen.2001.7695