Abstract
Simple SummaryIn wild mammals, chemical senses are crucial to survival, but sensory system information is lacking for many species, including the meerkat (Suricata suricatta), an iconic mammal with a marked social hierarchy that has been ambiguously classified in both canid and felid families. We studied the neuroanatomical basis of the meerkat olfactory and accessory olfactory bulbs, aiming to provide information on the relevance of both systems to the behaviors of this species and contributing to improving its taxonomic classification. The accessory olfactory bulb serves as the integration center of vomeronasal information. When examined microscopically, the accessory olfactory bulb of the meerkat presents a lamination pattern more defined than observed in dogs and approaching the pattern described in cats. The degree of lamination and development in the meerkat main olfactory bulb is comparable to the general pattern observed in mammals but with numerous specific features. Our study supports the functionality of the olfactory and vomeronasal integrative centers in meerkats and places this species within the suborder Feliformia. Our study also confirms the importance of chemical signals in mediating the social behaviors of this species and provides essential neuroanatomical information for understanding the functioning of their chemical senses.We approached the study of the main (MOB) and accessory olfactory bulbs (AOB) of the meerkat (Suricata suricatta) aiming to fill important gaps in knowledge regarding the neuroanatomical basis of olfactory and pheromonal signal processing in this iconic species. Microdissection techniques were used to extract the olfactory bulbs. The samples were subjected to hematoxylin-eosin and Nissl stains, histochemical (Ulex europaeus agglutinin, Lycopersicon esculentum agglutinin) and immunohistochemical labelling (Gαo, Gαi2, calretinin, calbindin, olfactory marker protein, glial fibrillary acidic protein, microtubule-associated protein 2, SMI-32, growth-associated protein 43). Microscopically, the meerkat AOB lamination pattern is more defined than the dog’s, approaching that described in cats, with well-defined glomeruli and a wide mitral-plexiform layer, with scattered main cells and granular cells organized in clusters. The degree of lamination and development of the meerkat MOB suggests a macrosmatic mammalian species. Calcium-binding proteins allow for the discrimination of atypical glomerular subpopulations in the olfactory limbus between the MOB and AOB. Our observations support AOB functionality in the meerkat, indicating chemosensory specialization for the detection of pheromones, as identified by the characterization of the V1R vomeronasal receptor family and the apparent deterioration of the V2R receptor family.
Highlights
The dense network of chemosignals recognized by the olfactory system enables the animal to form a multidimensional rendering of its environment [1], information often used to modulate basic activities, such as reproduction, food-seeking, and the adoption of social, maternal, and sexual behaviors [2]
The sample was directly fixed in formaldehyde, the nasal cavity was cut transversely to observe the topography of the vomeronasal organ, and the anterior part of the skull was removed so that, after removing the frontal lobes, the olfactory bulbs could be examined in situ
The cross-sectioning of the nasal cavity at the level of the first premolar allowed us to appreciate the development of the nasal septum, the dorsal and ventral nasal turbinates, and the presence of the vomeronasal organ (VNO), which is located in the ventral region of the nasal septum on both sides of the vomer bone (Figure 1C)
Summary
The dense network of chemosignals recognized by the olfactory system enables the animal to form a multidimensional rendering of its environment [1], information often used to modulate basic activities, such as reproduction, food-seeking, and the adoption of social, maternal, and sexual behaviors [2]. This environmental rendering is not static but dynamic in space and time. Both organs are distinguished by the anatomical distributions of their sensory neurons, the types of receptors they express, the signaling mechanisms they employ to transduce chemosensory stimuli, the types of chemosensory stimuli they detect, and the axonal targets of their sensory neurons in the rhinencephalon [8]
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