Beyond Terrestrial Carnivores: Olfactory Bulb Anatomy in a Semi-Aquatic Mammal

The Asian small-clawed otter (Aonyx cinereus) has a highly developed, well-laminated main olfactory bulb but a small, poorly laminated accessory olfactory bulb.

• Why it matters: Olfactory system organization is poorly known in mustelids, especially lutrines adapted to semiaquatic habitats, limiting understanding of how chemosensory pathways evolve.
• What they did: The authors examined serial transverse and sagittal sections of the main and accessory olfactory bulbs using Nissl and Tolivia staining, a panel of lectins, and neuronal/olfactory immunohistochemical markers.
• The result: The accessory bulb’s glomerular-like structures were supported by selective Ulex europaeus agglutinin binding and strong Gi2 immunoreactivity, with weak Go labeling, indicating a retained but structurally reduced vomeronasal pathway.

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