Maternally Derived Yolk Hormones Vary in Follicles of the Painted Turtle, Chrysemys picta RACHEL M. BOWDEN, 1,2 * MICHAEL A. EWERT, 1 STEVEN FREEDBERG, 1 AND CRAIG E. NELSON 1,2 1 Department of Biology, Indiana University, Bloomington, Indiana 47405 -3700 2 Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, Indiana 47405 -3700 ABSTRACT The transfer of hormones from a female to her o¡spring is known to occur in egg laying vertebrates, and the potential for these early, maternally derived hormones to in£uence sex de- termination in reptiles with temperature-dependent sex determination is intriguing. In the present study, we examine variation in the concentrations of progesterone, testosterone, and estradiol among three follicle size classes within a female painted turtle (Chrysemys picta) and among females across four periods that span the pre- to post-nesting season. Females were collected, and both follicles and shelled eggs (when present) were harvested for hormone analysis. Progesterone levels did not vary seasonally. However, the concentration of progesterone did vary among and within follicle classes, and was primarily dependent upon ovulatory state: Recently ovulated follicles (as yolks within shelled eggs) contained signi¢cantly more progesterone than unovulated follicles. Concentrations of testoster- one were low and did not vary either among size classes or across the season. Estradiol levels decreased with increasing follicle size and were higher later in the nesting season.Thus, hormone concentrations varied among follicle sizes and states but in patterns that di¡ered among hormones.This variation has the potential to in£uence sex determination. J. Exp. Zool. 293:67^72, 2002. r 2002 Wiley-Liss, Inc. In egg laying vertebrates, hormones can pass from the female to her o¡spring through the trans- fer of yolk. This transfer of maternal hormones could have direct implications for o¡spring pheno- type and ¢tness, but few studies have examined this potential. In red-winged black birds (Agelaius phoe- niceus), increased yolk testosterone has been linked to an increase in the size of the hatching muscle, which in turn could result in decreased hatching time, thus resulting in reduced stress on the hatch- ing and an increase in hatching success (Lipar and Ketterson, 2000). In reptiles with temperature-de- pendent sex determination (TSD), variation in yolk hormone levels among clutches may mediate mater- nal e¡ects on sex determination, perhaps allowing female condition to alter o¡spring sex ratio (Conley et al.,’97; Roosenburg and Niewiarowski,’98; Bow- den et al., 2000, 2001). In eggs from clutches of the painted turtle (Chrysemys picta) incubated at the local pivotal temperature (the temperature that results in a 1:1 sex ratio), we previously demon- strated seasonal variation in clutch sex ratios and in the ratio of estradiol to testosterone. More male- biased clutches were produced early in the season when the estradiol:testosterone ratio was low, and more female-biased clutches were produced late in the season when the ratio was high (Bowden et al., 2000).We have since replicated the correlated seaso- nal shifts in both hormones and sex in a second year (Bowden et al., 2001). Partly in pursuit of an understanding of these seasonal shifts in hormone levels, we previously de- termined that there are hormonally heterogeneous layers within the yolk of C. picta and the red-eared slider turtle, Trachemys scripta elegans (Bowden et al., 2001). In both species, estradiol was more con- centrated in the internal portions of the yolk, while progesterone and testosterone were most concen- trated in the external portion of the yolk. We as- sessed hormone levels across the nesting season in C. picta. Estradiol levels were signi¢cantly lower in all layers of eggs laid early in the nesting season when compared to eggs laid later in the nesting sea- son and, again, estradiol was most concentrated in the inner layers of yolk, but signi¢cantly so only in late season eggs (Bowden et al., 2001). *Correspondence to: Rachel M. Bowden, Department of Zoology & Genetics, Iowa State University, 339 Science II, Ames, IA 50011-3223. E-mail: rbowden@iastate.edu Received 7 June 2001; Accepted 14 January 2002 Published online in Wiley InterScience (www.interscience.wiley. com). DOI: 10.1002/jez.10094 r 2002 WILEY-LISS, INC. JOURNAL OF EXPERIMENTAL ZOOLOGY 293:67–72 (2002)