Thesis Title

Investigating the Effects of Vinclozolin on Reproduction in Three Generations of Sigmodon Hispidus

Date of Graduation

Summer 2004


Master of Science in Biology



Committee Chair

Thomas Tomasi


vinclozolin, cotton rat, Sigmodon hispidus, antiandrogren, reproduction

Subject Categories



Sigmodon hispidus (n=48) were trapped from four locations in Southwest Missouri. They were housed in cages in environmental chambers so that seasons could be simulated, inducing breeding. Their offspring (the PG eneration) were given the same food, but their water bottles were "spiked" with vinclozolin, an antiandrogenic fungicide. There were four treatment groups: a high-, medium-, and low-dose group, and a control group that drank distilled water. Each generation bred with non-littermates within the same treatment. The P's gave rise to the F1 generation, which bred to produce the F2 generation. Comparisons were made between generations (as the P was exposed to treatment only upon weaning, whereas the F1 and F2 generations were exposed in utero, as well as the remainder of their lives), between treatment groups, and between genders. Free and total plasma testosterone levels were compared. Sperm production in the seminiferous tubules of the testes (collected during necropsy, embedded, sectioned, and placed on slides for examination) allowed a sperm index for comparison. Other comparisons included body mass on days 2, 14, 30, 45, 60, and 75. Additional comparisons included mother's age and litter sizes, mean pup mass, total reproductive mass (TRM), paired gonad mass (PGM), paired testes volume (PTV) and anogenital distance. The following significant differences (P<0.05) were noted: the F2 were born in larger litters than the P generation; F2 animals had lower PGM and PTV than the F1 cotton rats; and lower TRM than both the P and F1 generations, and the F1 and F2 generations had lower sperm indeces than the P animals. Significant treatment effects were on growth, inclding medium-dose having lower mass than the control group at day 14, and lower mass than both the high-dose and control groups at days 30 and 75. All other findings were statistically insignificant.


© Barbara J. Hannah