Meeting Abstract
38.3 Friday, Jan. 4 Experimental manipulation of prenatal sex ratio using photoperiod in Siberian hamsters NAVARA, Kristen J.*; WORKMAN , Joanna L.; NELSON, Randy J.; The University of Georgia; The Ohio State University; The Ohio State University knavara@uga.edu
Natural selection should favor maternal control over the sex ratio of offspring, allowing females to tailor sex ratios to environmental cues. Seasonal fluctuations in resource availability create energetic challenges that influence reproductive strategies employed by females. Thus we would expect seasonal variation in sex ratios, which is supported by studies in several species. The mechanisms behind such control remain unclear and the first step is isolating one cue by which females adjust offspring sex. Siberian hamsters (Phodopus sungorus) are seasonal animals that base much of their physiology on a predictor of seasonal change � photoperiod. We hypothesized that female hamsters would skew offspring sex ratio towards males when maintained in short, winter-like day lengths (8h light:16h dark)(SD), which is predictive of low food availability, compared to hamsters in long, summer-like day lengths (16h light:8h dark)(LD). In experiment 1, hamsters born in LDs were paired and either maintained in LDs (25 pairs) or immediately transferred to SDs (25 pairs). Weanlings were collected from two consecutive litters and sexed by dissection. Sex ratios of offspring conceived after initial pairing were not skewed in either group. However, sex ratios of offspring conceived approximately 25 days after transfer were significantly skewed towards males in the SD group, but not the LD group. In experiment 2, the 25 pairs in SDs were allowed to conceive again, after which pregnant females were killed and fetuses collected and molecularly sexed. Fetal sex ratios were significantly skewed towards males, suggesting that sex ratio adjustment occurs before birth in this species and in response to a single environmental cue. Potential mechanisms will be discussed.
