PM11 Wildlife Ecotoxicology
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(PM176) Window of sensitivity when the phenotypic sex of male fence lizards can be altered.

Talent, L1, Cooper, N1, Redick, M1, Janz, D2, 1 Oklahoma State University, Stillwater, Oklahoma, USA2 University of Saskatchewan, Saskatoon, Saskatchewan, Canada

ABSTRACT- Lizards have potential as laboratory models for evaluating the effects of estrogenic, androgenic, and thyroid affecting chemicals on reptiles. We are evaluating eastern (Sceloporus undulatus) and western fence lizards (S. occidentalis) as candidates for a laboratory reptile model. Prior research determined that the phenotypic sex of male fence lizards can be feminized by in ovo exposure to an estrogenic chemical. This research was designed to determine the age when development of secondary sex characteristics (i.e. presence of enlarged post-anal scales) in male embryos could be prevented by in ovo exposure to an estrogenic chemical. Eggs were collected from a laboratory population of fence lizards on the day of oviposition and incubated on moist perlite at 30°C. Starting on day two of incubation and continuing on all even numbered days until day 34, eggs were injected with amounts of 17-ethinylestradiol that ranged from 0.00001 to 0.0001 g/egg. For each day of incubation that eggs were injected, 20 eggs of both species were injected for each amount of 17-ethinylestradiol used. Treated eastern and western fence lizard embryos responded similarly. The phenotypic sex of males could be changed until embryos were about 22 days into incubation. The most sensitive incubation stage for both species was between day 10 and 16 of incubation. The window of sensitivity to an estrogenic chemical will probably vary for other endpoints such as behavior, gonadal development, and hemipenal development.

Key words: estrogenic chemical, reptiles, lizard, phenotypic sex

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