title: Complex flow in the nasal region of guitarfishes.
abstract: Scent detection in an aquatic environment is dependent on the movement of water. We set out to determine the mechanisms for moving water through the olfactory organ of guitarfishes (Rhinobatidae, Chondrichthyes) with open nasal cavities. We found at least two. In the first mechanism, which we identified by observing dye movement in the nasal region of a life-sized physical model of the head of Rhinobatos lentiginosus mounted in a flume, olfactory flow is generated by the guitarfish's motion relative to water, e.g. when it swims. We suggest that the pressure difference responsible for motion-driven olfactory flow is caused by the guitarfish's nasal flaps, which create a region of high pressure at the incurrent nostril, and a region of low pressure in and behind the nasal cavity. Vortical structures in the nasal region associated with motion-driven flow may encourage passage of water through the nasal cavity and its sensory channels, and may also reduce the cost of swimming. The arrangement of vortical structures is reminiscent of aircraft wing vortices. In the second mechanism, which we identified by observing dye movement in the nasal regions of living specimens of Glaucostegus typus, the guitarfish's respiratory pump draws flow through the olfactory organ in a rhythmic (0.5-2 Hz), but continuous, fashion. Consequently, the respiratory pump will maintain olfactory flow whether the guitarfish is swimming or at rest. Based on our results, we propose a model for olfactory flow in guitarfishes with open nasal cavities, and suggest other neoselachians which this model might apply to.
authors.affiliation: Department of Mechanical Engineering, University of Bath, Bath BA2 7AY, UK.
authors.forename: Mawuli P K
authors.initials: MP
authors.lastname: Agbesi
authors.affiliation: Heron Island Research Station, The University of Queensland, Queensland 4680, Australia.
authors.forename: Sara
authors.initials: S
authors.lastname: Naylor
authors.affiliation: Heron Island Research Station, The University of Queensland, Queensland 4680, Australia.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Perkins
authors.affiliation: Department of Mechanical Engineering, University of Bath, Bath BA2 7AY, UK.
authors.forename: Heather S
authors.initials: HS
authors.lastname: Borsuk
authors.affiliation: Imaging and Analysis Centre, Natural History Museum, Cromwell Road, London SW7 5BD, UK.
authors.forename: Dan
authors.initials: D
authors.lastname: Sykes
authors.affiliation: Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK.
authors.forename: James S
authors.initials: JS
authors.lastname: Maclaine
authors.affiliation: Department of Mechanical Engineering, University of Bath, Bath BA2 7AY, UK.
authors.forename: Zhijin
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Chemistry, University of Bath, Bath BA2 7AY, UK. Electronic address: j.p.l.cox@bath.ac.uk.
authors.forename: Jonathan P L
authors.initials: JP
authors.lastname: Cox
mesh_terms: D000818:Animals; D005399:Fishes / Q000378:metabolism / Q000502:physiology*; D009296:Nasal Cavity / Q000378:metabolism / Q000502:physiology*; D012119:Respiration; D012903:Smell / Q000502:physiology*; D013550:Swimming / Q000502:physiology; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water
keywords: Elasmobranch; Fluid dynamics; Image processing; Olfaction; Ray; Reynolds number; Three-dimensional printing; X-ray microcomputed tomography