Morphology of a Shark Nose

Overview

The gross morphology of the nasal region of a fish determines how flow behaves in this region, and therefore has an important influence on the fish's olfactory abilities (sense of smell). Life-sized rapid prototype models were generated from a 200 µm resolution CT scan which enabled the functional morphology to be investigated within a flow tank. This allowed researchers to explore how the different channels and grooves effect the water circulation within the nasal cavities.

Characteristics:

  • Using CT to accurately build physical models featuring internal features
  • Creation of highly accurate STL files representing the shark head and nasal cavities
  • Rapid prototyping was used to create plastic models which could be used with in a flow tank

Thanks to

Natural History Museum, London: R. Abel, J. Maclaine • University of Cambridge: T. Nickels, T. Clark • University of Bath: Z. Wang, J. Cox

Image Acquisition

After removal of the specimen from the preservative it was mounted for CT scanning. Scanning was performed using an HMXST 225 CT system (Metris X-Tek, Tring, UK). The X-rays were generated from a tungsten target using a voltage and current of 180 kV and 105 µA, respectively. The radial projections were reconstructed into a three-dimensional matrix of 1897×1830×630 (L×W×H) 124.5 µm cubic voxels.

STL Generation

The DICOM images were imported into ScanIP. The Floodfill segmentation tool was used to fill unwanted internal cavities whilst preserving the nasal cavity. Some features in the olfactory chamber were manually refined using the Paint tool. To generate the STL file, volume and topology preserving smoothing was utilised to smooth the segmentation without losing the small features of the lamellae.

Simulation

The resulting plastic models created from the STL files were then placed in a water flow tank. Varying water flow rates were used to investigate how the features of the sharks head affected the direction of the water flow into the nasal cavities. A dye was used to help visualise the flow. It was found that the exterior channels and grooves directed water into the nasal cavity which then circulates before exiting from a different opening. Videos