Novel Nasal Anatomy Suggests Enhanced Olfactory Acuity in Auchenoglanidid Catfishes (Siluriformes: Auchenoglanididae)

We describe the olfactory chamber and histology of the olfactory epithelium in the auchenoglanidid catfish, Parauchenoglanis punctatus . Unlike the olfactory anatomy of non-auchenoglanidid catfishes, in all auchenoglanidids the olfactory rosette is elevated on a membrane suspended over the anterior portion of a large accessory sac. Scanning electron microscopy and histology show an array of long non-sensory cilia are present, likely maintaining flow of water over the rosette. Microvillar and ciliary sensory cells are regionalized in the folds of the lamellae. Combining dissection with reconstruction of the olfactory chamber, membrane, rosette, and accessory sac using contrast-enhanced CT scanning of soft tissue and supporting osteology suggests a novel “sniffing” mechanism may represent the primary means of drawing water and odorants into the olfactory chamber, and that specializations of the olfactory anatomy in this family function in flow augmentation into and around the olfactory chamber, maximizing the entrainment of odorants over the olfactory epithelium.