title: Motion-driven flow in an unusual piscine nasal region.
abstract: Fishes have several means of moving water to effect odorant transport to their olfactory epithelium ('olfactory flow'). Here we show that olfactory flow in the adult garpike Belone belone (Belonidae, Teleostei), a fish with an unusual nasal region, can be generated by its motion relative to water (swimming, or an external current, or both). We also show how the unusual features of the garpike's nasal region influence olfactory flow. These features comprise a triangular nasal cavity in which the olfactory epithelium is exposed to the external environment, a papilla situated within the nasal cavity, and an elongated ventral apex. To perform our investigation we first generated life-like plastic models of garpike heads from X-ray scans of preserved specimens. We then suspended these models in a flume and flowed water over them to simulate swimming. By directing filaments of dye at the static models, we were able to visualise flow in the nasal regions at physiologically relevant Reynolds numbers (700-2,000). We found that flow of water over the heads did cause circulation in the nasal cavity. Vortices may assist in this circulation. The pattern of olfactory flow was influenced by morphological variations and the asymmetry of the nasal region. The unusual features of the nasal region may improve odorant sampling in the garpike, by dispersing flow over the olfactory epithelium and by creating favourable conditions for odorant transport (e.g. steep velocity gradients). Unexpectedly, we found that the mouth and the base of the garpike's jaws may assist the sampling process. Thus, despite its apparent simplicity, the garpike's nasal region is likely to act as an effective trap for odorant molecules.
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: Department of Mechanical Engineering, University of Bath, Bath, BA2 7AY, UK.
authors.forename: Heather S
authors.initials: HS
authors.lastname: Borsuk
authors.affiliation: Jeremy Hunt Design, Unit A6, 66 Norlington Road, London, E10 6LA, UK.
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Hunt
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: Imaging and Analysis Centre, Natural History Museum, Cromwell Road, London, SW7 5BD, UK.
authors.forename: Richard L
authors.initials: RL
authors.lastname: Abel
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: Nikon Metrology, Icknield Way, Tring, Hertfordshire HP23 4JX, UK.
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Ramsey
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 / Q000033:anatomy & histology* / Q000502:physiology*; D006257:Head; D008953:Models, Anatomic; D009666:Nose / Q000033:anatomy & histology* / Q000502:physiology*; D012903:Smell; D013550:Swimming; D014872:Water Movements
keywords: Beloniform; Fluid dynamics; Needlefish; Olfaction; X-ray microcomputed tomography