LOVERN, M.B.*; WADE, J.; Michigan State Univ., East Lansing; Michigan State Univ., East Lansing: Relationship among sex steroid levels in breeding female plasma, yolk, and embryonic tissue in green anole lizards

Sex steroids have been documented in the egg yolks of numerous birds and reptiles, but why they are there remains an open question. Steroids may be present in yolk simply as a byproduct of the hormonal regulation of maternal physiology, due to passive uptake during yolk formation. Alternatively, yolk steroids may have been selected because of some advantage conferred to the offspring. If mothers have the ability to actively regulate yolk steroid deposition, then steroid profiles in maternal circulation and in yolk need not be associated, and therefore may be independently selected for their roles in maternal physiology and offspring development. To explore this possibility, we examined testosterone (T) and estradiol (E) concentrations in the plasma and yolking follicles of breeding female green anoles, and in whole embryos and yolks at several developmental stages, by radioimmunoassay. Our initial results indicate that plasma and yolk concentrations of T and E are not correlated. Furthermore, in adult females plasma T levels are less than half those of E, whereas in both yolk and embryos T levels are more than double those of E. These results demonstrate that steroid levels to which adult females and their embryos are exposed can be uncoupled, thereby revealing a potential mechanism that allows steroid levels to maximally benefit both mother and offspring.