Quick Dips

Electric Sharks

Getting inside a shark's head might be a scary thought, but it's all in a day's work for an Otago University PhD student and the AgResearch Invermay CT scanning team.

The "InnerVision" CT scanner is more traditionally used for scanning sheep, to identify lean and meaty animals for breeding purposes. It is one of only six scanners in the world being used to measure the body composition of animals, and is now also proving very useful in the study of the electric sense of sharks and the role that this plays in their navigation. Eventually it should provide information on how sharks navigate when they migrate.

It is thought the Earth's magnetic field influences the migration of sharks and other migratory animals such as birds, but little is known about the sensory structures used to detect the field. Sharks possess an electric sense which may have an important role, so research into this may improve understanding of the mechanisms used by other species. To do this, Rachel Berquist needs to examine the "canals" these electric senses use in the shark's head.

CT scanning gives very clear cross-sectional X-ray images of bone and tissue without the need to actually cut into the sample, so Berquist thought she'd try using the InnerVision scanner to see how well the structures in the head could show up in a carpet shark, examining how these canals connect and how they contrast with surrounding tissue.

An exploratory scan gave her a very good reconstruction of the shark's head, including the teeth, and provided interesting information on its structure, which may also be useful to research into shark brains. Further scans using a contrasting agent to highlight the canals will hopefully provide a more detailed look at the components of the shark brain.

"The quality of the image given by a CT scanner is really quite amazing. For instance, using simple adjustments, I was able to zoom in on a particular feature, and rotate it to get a 360^o view," says Berquist. "The possibilities for using this technology to assist research are very promising."