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

Recent studies have suggested that the relatively large size of the vomeron asal 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), captur ed between June and August, 1998. The heads were prepared histologically fo r serial sectioning at 10-16 mum, and stained with hematoxylin and eosin. S ections were examined by light microscopy, and the VNNE was quantified for each specimen using a computer 3-dimensional reconstruction technique. Rece ptor cells also were quantified with a Leica photomicroscope using an ocula r grid calibrated by a stage micrometer. No (P > 0.05) differences occurred between species for length or volume of the VNNE when expressed as absolut e measures or as ratios of somatic measures. No (P > 0.05) differences occu rred in receptor population between species. Although testicular weight see med to show a positive allometric relationship with body size, no such asso ciation was seen for VNNE measurements. Our results do not support the hypo thesis that VNNE size is associated negatively with the level of parental c are 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.