Histology and Ultrastructure of Olfactory and Nasal Respiratory Mucosae in Suckling and Adult African Grasscutters (Thryonomys swinderianus- Temminck, 1827)

Abstract

Abstract Glasscutters (GRCs) are hystricognath rodents that predominate West African countries where they are captured and bred in captivity as “microlivestock” and for research. Consequently, research priority has, of late, shifted to aspects of GRC biology particularly with regard to morphofunctional aspects of its body systems. The olfactory system plays critical roles in regulating social, sexual, maternal and feeding behaviors. This study examines, histologically and ultrastructurally, the pattern and magnitude of remodeling of the GRC olfactory mucosa (OM) and nasal respiratory mucosa (NRM) between suckling and adult ages and compares these with what is documented for other mammals. In the adults, tubular-type Bowman’s glands, olfactory receptor neuron (ORN) axon bundles and blood vessels were uniformly distributed in the OM lamina propria contrary to sucklings where acinar-type Bowman’s glands lay superficially and the bundles relatively deeper. Apically in the adult NRM epithelium, ciliated and non-ciliated cells were uniformly distributed contrary to the sucklings where linearly arranged ciliated cell separated large numbers of non-ciliated cells. Quantitatively between the suckling and adult ages, respective increment values (%) were 28.2, 23.0, 28.1 and 52.9 for OM epithelial thickness, axon bundle diameter, ORN packing density and cilia number/ ORN dendritic knob. Age-related increment in volume density (%) was 53.9, 31.6, 19.4 and 46.3 for Bowman’s glands, axon bundles, OM vessels and NRM glands respectively. We conclude that microstructural refinement of the OM and NRM varies in qualitative and quantitative detail depending on age and species and that phenotypic plasticity in these structures suggests environmentally driven morphology.