![]() ![]() This unique head morphology provides a wide lateral separation between olfactory organs that may be used by the shark to resolve spatial gradients in odorant concentration, resulting in enhanced bilateral sampling for olfactory tropotaxis. Externally, one of the most distinguishable features of the Sphyrnidae family is the broad, flat head known as a cephalofoil. Such studies – have provided insight into how different anatomical structures may contribute to olfaction. The olfactory chamber of the hammerhead shark is an extremely complex organ that to date has largely been studied on a morphological basis. Consequently, the hammerhead shark appears to utilize external (major and minor nasal grooves) and internal (apical gap) flow regulation mechanisms to limit water flow between the olfactory lamellae, thus protecting these delicate structures from otherwise high flow rates incurred by sampling a larger area. Internal hydrodynamic flow patterns are also revealed, where we show that flow rates within the sensory channels between olfactory lamellae are passively regulated by the apical gap, which functions as a partial bypass for flow in the olfactory chamber. Further, both the major and minor nasal grooves redirect some flow away from the incurrent nostril, thereby limiting the amount of fluid that enters the olfactory chamber. The major (prenarial) nasal groove along the cephalofoil is shown to facilitate sampling of a large spatial extent (i.e., an extended hydrodynamic “reach”) by directing oncoming flow towards the incurrent nostril. Computed external flow patterns elucidate the occurrence of flow phenomena that result in high and low pressures at the incurrent and excurrent nostrils, respectively, which induces flow through the olfactory chamber. Computational fluid dynamics simulations of water flow in the reconstructed model reveal the external and internal hydrodynamics of olfaction during swimming. Here we investigate the hydrodynamics of olfaction in Sphyrna tudes based on an anatomically-accurate reconstruction of the head and olfactory chamber from high-resolution micro-CT and MRI scans of a cadaver specimen. Thus, odorant transport from the aquatic environment to the sensory epithelium is the first critical step in olfaction. Functionally, for the shark to detect chemical stimuli, water-borne odors must reach the olfactory sensory epithelium that lines these lamellae. The olfactory chambers, located at the distal ends of the cephalofoil, contain numerous lamellae that increase the surface area for olfaction. The hammerhead shark possesses a unique head morphology that is thought to facilitate enhanced olfactory performance. ![]()
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