Gross and histological study of nasal and brain olfactory structures in the grasscutter (Thryonomys swinderianus, Temminck)

Abstract

The major drawback of the efforts currently being made to domesticate grasscutters (GRCs) is the paucity of data on their biology particularly in connection with sensory related reactions. We investigated, both grossly and histologically, the qualitative and quantitative features of the GRC nasal and brain olfactory components with a view to understanding their morphofunctional adaptations. At the caudal roof of the nasal cavity, the olfactory mucosa (OM), whose basic histology was similar to that of other mammals, covered a set of five cylindrical-shaped ethmoturbinates. Olfactory bulb (OB) and olfactory brain components (OBC) (i.e., OB, olfactory tract and stria) constituted 0.55 and 1.26% of the entire brain volume respectively. Relative to the cerebral hemispheres, respective proportions for lengths and breadths were 72.23% for OBC and 34.38% for OB. Regarding the OM, epithelial height and axon bundle diameters were 76.3 ± 5.4 µm and 70.6 ± 8.6 µm respectively while volume fractions were 31.2 ± 4.4% for the bundles and 49.7 ± 5.1% for Bowman’s glands. These findings reveal that the anatomical design of the GRC OM and OBC follows the general patterns observed in other mammals and are refined to levels that appear to correspond to demands in olfactory function vis-à-vis behavior and ecology.