The brain of the African wild dog. II. The olfactory system

Abstract

Employing a range of neuroanatomical stains, we detail the organization of the main and accessory olfactory systems of the African wild dog. The organization of both these systems follows that typically observed in mammals, but variations of interest were noted. Within the main olfactory bulb, the size of the glomeruli, at approximately 350 μm in diameter, are on the larger end of the range observed across mammals. In addition, we estimate that approximately 3,500 glomeruli are present in each main olfactory bulb. This larger main olfactory bulb glomerular size and number of glomeruli indicates that enhanced peripheral processing of a broad range of odorants is occurring in the main olfactory bulb of the African wild dog. Within the accessory olfactory bulb, the glomeruli did not appear distinct, rather forming a homogenous syncytia‐like arrangement as seen in the domestic dog. In addition, the laminar organization of the deeper layers of the accessory olfactory bulb was indistinct, perhaps as a consequence of the altered architecture of the glomeruli. This arrangement of glomeruli indicates that rather than parcellating the processing of semiochemicals peripherally, these odorants may be processed in a more nuanced and combinatorial manner in the periphery, allowing for more rapid and precise behavioral responses as required in the highly social group structure observed in the African wild dog. While having a similar organization to that of other mammals, the olfactory system of the African wild dog has certain features that appear to correlate to their environmental niche.

Neuroanatomical and Immunohistological Study of the Main and Accessory Olfactory Bulbs of the Meerkat (Suricata suricatta)

“…AOB principal cells showed no immunostaining for either calcium-binding protein, similar to observations reported for the opossum [ 80 ], mouse [ 56 ], rat [ 126 ], and African wild dog, although in AOB of the latter species only CR expression was studied [ 46 ]. Overall, the anti-CR staining pattern observed in the AOB meerkat was similar to those observed in the rat [ 126 ], opossum [ 80 ], and African wild dog [ 46 ], whereas the pangolin displays a higher density of cellular elements and fibers, especially in the granular layer [ 47 ]. Anti-CB labelling observed in the surface layers of the AOB revealed more significant interspecies differences than anti-CR labelling.…”

“…The relevance of chemical communication in meerkats indicates the importance of obtaining accurate neuroanatomical information regarding the structures of the meerkat MOS and VNS, which can be contrasted with available information for domestic carnivores, such as the cat [ 43 ] and dog [ 44 , 45 ]; wild carnivores, such as the African wild dog [ 46 ]; and with species belonging to the order Pholidota, a sister order to Carnivora, such as the pangolin [ 47 ]. We performed a comprehensive morphological, histological, and immunohistochemical study of meerkats with the aim of characterizing the neuroanatomical features of the first neural integrative centers of olfactory and vomeronasal information, the OB, and its main and accessory components.…”

The brain of the African wild dog. III. The auditory system

“…The sections used for myelin staining were refrigerated for 2 weeks in 5% formalin then mounted on 1.0% gelatin‐coated slides and stained with a modified silver stain (Gallyas, 1979). Full details of the immunostaining protocol, and the characterization and specificity of the antibodies used in the current study are provided in an early publication (Chengetanai, Bhagwandin, et al, 2020b) and are not repeated here (see Table 1 for a synopsis of antibody characterization and use in the current study).…”

“…The observations made to date regarding auditory abilities in the African wild dog (see above) hint at the potential for specialization of this system, such as relatively enlarged regional auditory complexes (e.g., Oelschläger, Ridgway, & Knauth, 2010), additional parcellation within nuclear (e.g., Maseko, Patzke, Fuxe, & Manger, 2013) or cortical regions (e.g., Kössl, Hechavarria, Voss, Schaefer, & Vater, 2015), increased neuronal densities within certain regions/areas/nuclei (e.g., Collins, Airey, Young, Leitch, & Kaas, 2010), or overt changes in the neurochemistry (e.g., Hof, Glezer, Nimchinsky, & Erwin, 2000). The current study therefore aimed to provide a detailed systems‐level description of the morphology, parcellation, and aspects of the chemical neuroanatomy of the auditory pathway in the African wild dog, as part of our survey of the structure of the African wild dog brain (Chengetanai, Tenley, et al, 2020a; Chengetanai, Bhagwandin, et al, 2020b), and to assess whether any systems‐level specializations of the auditory system is present in this species.…”

The brain of the African wild dog.IV. The visual system

“…The sections used for myelin staining, were refrigerated for 2 weeks in 5% formalin then mounted on 1% gelatine coated slides and stained with a modified silver stain (Gallyas, 1979). Full details of the immunostaining protocol, and the characterization and specificity of the antibodies used in the current study are provided in an early publication (Chengetanai et al, 2020a) and are not repeated here (see Table 1 for a synopsis of antibody characterization and use in the current study).…”