T. Rhen et al., Effects of testosterone on sexual behavior and morphology in adult female leopard geckos, Eublepharis macularius, HORMONE BEH, 36(2), 1999, pp. 119-128
The leopard gecko, Eublepharis macularius, is a species in which testostero
ne (T) is the primary circulating sex hormone in adults of both sexes. Ther
e are, however, sex differences in T physiology. Whereas males have prolong
ed periods with high T levels, T levels cycle in accord with follicular dev
elopment in females. Specifically, T concentration increases during vitello
genesis, drops after ovulation, and then remains at previtellogenic levels
until eggs are laid and the next follicular cycle begins. To determine the
function of T in females, we manipulated both the level and the duration of
T elevation using Silastic implants in intact, adult female leopard geckos
. Females had low (similar to 1 ng/ml), medium (similar to 100 ng/ml), or h
igh (similar to 200 ng/ml) T levels for either a short (8 days) or a long (
35 days) duration. Behavior tests with males were conducted on days 1-5 in
the short-duration group or on days 29-33 in the long-duration group. For b
oth short- and long-duration groups, T treatment decreased attractivity in
females with medium and high T levels compared to females with low T levels
. In contrast, females with a medium T level were more receptive than femal
es with a low T level in the short-duration group. Females in the long-dura
tion group were unreceptive regardless of T level. Females treated for a lo
ng duration also displayed more aggression toward and evoked more aggressio
n from males than short duration females. Short-duration T treatment had no
masculinizing effect on female morphology, whereas medium and high T level
s for a long duration induced development of hemipenes. Overall, these resu
lts suggest that T can both increase and decrease sexual behaviors in the f
emale leopard gecko. (C) 1999 Academic Press.