PMC

Gross morphology and histology of the olfactory organ of P. antarcticum. (a) Partially dissected head with the olfactory rosette visible in place in the olfactory chamber. The three white lines indicate the cutting plane in (c,d), and in (asterisk). (b) A dissected olfactory rosette showing the two unequal rows of lamellae. Anteriorly, the slightly lacerated tissue where the rosette was attached dorsally to the roof of the nasal chamber is visible. (c) Histological section of the olfactory chamber (asterisks) with the olfactory rosette, anterior to the opening of the nostril. The olfactory rosette is fused ventrally to the floor of the chamber and dorsally to its roof. The lamellae are not enveloped in a capsule nor fused with the wall of the olfactory chamber. A branch of the accessory nasal sac is visible in the low-right corner of the picture (double asterisk). (d) Histological section of the olfactory chamber with olfactory rosette, at the level of the opening of the nostril. The olfactory rosette is attached only to the floor of the olfactory chamber. FO = fila olfactoria; L = lamellae; N = nostril; ON = olfactory nerve; OR = olfactory rosette; R = raphe.

Developing olfactory epithelium after hatching in P. senegalus (A — 96 h AF, B — 98 h AF, C,D — 120 h AF), TEM. A Olfactory epithelium with primary (placodal) supporting cells (psc) and developing olfactory receptor neurons (orn) with intracellular primary cilia (ipc). B Extension of the primary olfactory cavity of the nasal sac (poc).C Dendritic ending of ciliated olfactory receptor neuron (corn) with projecting cilium. D Disintegrating junctional complex of the olfactory epithelium close to the primary lumen.

Early development of the olfactory placode in P. senegalus. Light Microscopy, semi-thin sections. A,B Early embryo 34 h AF, parasagittal section showing early placode formation. C Cone-shaped ingrowth of the thickened placode in 52 h AF (transversal section). D Formation of the primary nasal sac and internal lumen 72 h AF (transversal section). agl- attachment gland, fb — forebrain, opl — olfactory placode, poc — primary olfactory cavity or lumen of the nasal sac.

The olfactory organ of lungfish stained with HE. (A) Sagittal section of the nasal sac of the lungfish showing many lamellae hanging from the roof. Recesses (arrows) are observed at the base of the lamellae and lined with the recess epithelium. A: anterior, D: dorsal, P: posterior, V: ventral. (B) The lamellar olfactory epithelium covering the lamellae. Neighboring lamellar olfactory epithelia are separated by non-sensory epithelium (asterisk). BC: basal cell, ORC: olfactory receptor cell, SP: supporting cell.