Meeting Abstract

P2.47  Friday, Jan. 4  Hydrodynamic flow through the nasal cavity of sharks TIMM, L.L.*; FISH, F.E.; West Chester University; West Chester University lori_timm@yahoo.com

The nasal cavity of sharks is a blind capsule. Water is envisioned to flow through the cavity in a smooth, continuous flow pattern. To understand the hydrodynamic flow through the nasal cavity, morphometric data were collected on several shark species from various habitats (i.e., pelagic vs. benthic). External morphological characteristics of the head were measured, as well as, internal measurements of the nasal cavity. The structure of the nostrils showed variation between habitats. Benthic species had a wider anterior nasal flap width than pelagic species. Pelagic species had a greater mouth to snout distance than benthic species. Examination of the hydrodynamic flow through the nasal cavity of the spiny dogfish (Squalus acanthias) was documented with flow tank experiments. The nasal cavity was exposed by dissection and a glass plate was glued on top of the cavity, allowing a complex, three-dimensional hydrodynamic flow to be observed. Water entered the incurrent nostril, flowed through the lamellae, crossed over and under the nasal valve (i.e., projection from the posterior nasal flap), and circulated around two points on the valve before exiting through the excurrent nostril. When the valve was removed, stalling and backflow of water were observed. The valve has a hydrodynamic function that allows for a discrete streamline of water to flow through the cavity without flow disruption. Continuous flow is provided by the valve in the nasal cavity for increased olfactory acuity. Head morphology is related to ecology, and in addition to the hydrodynamic flow through the nasal cavity, may give more insight to the evolutionary history of sharks.