Size of the vomeronasal neuroepithelium in two species of Microtus with differing levels of paternal behavior

Abstract

Recent studies have suggested that the relatively large size of the vomeronasal neuroepithelium (VNNE) in the male mammal may be related inversely to the amount of parental care contributed. We tested this hypothesis using 2 species of Microtus that differ in reproductive strategies and in level of care of the offspring. We studied the nasal tissues of 8 male meadow voles (Microtus pennsylvanicus) and 8 male prairie voles (M. ochrogaster), captured between June and August, 1998. The heads were prepared histologically for serial sectioning at 10-16 μm, and stained with hematoxylin and eosin. Sections were examined by light microscopy, and the VNNE was quantified for each specimen using a computer 3-dimensional reconstruction technique. Receptor cells also were quantified with a Leica photomicroscope using an ocular grid calibrated by a stage micrometer. No (P > 0.05) differences occurred between species for length or volume of the VNNE when expressed as absolute measures or as ratios of somatic measures. No (P > 0.05) differences occurred in receptor population between species. Although testicular weight seemed to show a positive allometric relationship with body size, no such association was seen for VNNE measurements. Our results do not support the hypothesis that VNNE size is associated negatively with the level of parental care by male voles. Multiple factors may influence size of the VNNE in wild Microtus, which likely include an interaction of the genome, behavior, and environment.