Exploring sharks' sens of smell with Jonathan Cox

Sharks have really sensitive noses – they can smell a drop of blood from almost 1km away – but how they’re able to do this has always been a puzzle. Laboratory News speak to the man who’s been studying hammerhead sharks in the hope of finding how the fish can smell so well

Using the latest technology and a scale model of a hammerhead shark, Dr Jonathan Cox – a lecturer in the department of chemistry at the University of Bath – has been looking into how sharks sniff out their prey. His research is the first to use a detailed model of the hammerhead shark to explore the creatures amazing sense of small, and has led Dr Cox to collaborate with the University of Cambridge and the Natural History Museum.

Sharks can smell blood from up to a kilometre away – how? Just why are their noses so sensitive?

Well, the kilometre thing is probably dependent on things like the direction of the current and the amount of blood. But shark noses are at least as sensitive as their canine counterparts. And the sensitivity almost certainly stems from the large sensory surface area compacted into the nose – the nasal surface of a small hammerhead is postcard-sized. But the question is, how are smells delivered efficiently to this surface area? In other words, how is thorough irrigation of these areas achieved? And that's what we're interested in.

We know you didn’t use a real shark, so how were you able to find this out?

We used a model! The model was generated from a CT scan of a hammerhead's head in the Natural History Museum's collections. It was collected by Ro McConnell in a scientific expedition off the coast of South America over 50 years ago.

Two very nice fellows from the Natural History Museum helped get the scan: James Maclaine picked out the specimen for me in the first place and Richie Abel did the CT scan. A company called Simpleware magically transformed the scan into a virtual head, which was then converted into a plastic model with a 3D printer. The model was put in water tunnels in Cambridge and Bath with a spot of dye to help see what was going on flow-wise in the nose. Tim Nickels (Cambridge University) and Zhijin Wang (University of Bath) helped a lot with these experiments.

What prompted your interest in this area?

A desire to make a super-sensitive artificial sniffing device. I started looking at fish noses as possible models for such devices after reading an article by a US scientist called Gary Settles. He pointed out that fish noses are very compact and, unlike are own, which get side-tracked by air-conditioning chores, do only one thing: smell. Eventually, after the dropping of many pennies, I turned to the shark's nose, the gold-standard for underwater olfaction

What are the practical applications of this research?

Other than super-sensitive underwater sniffing devices, the applications are endless: detection of explosives, underwater energy sources, pollutants; monitoring the health of the oceans; bench-top devices for medical applications, and so on.

Tell us about what else you do at the University Bath?

If you mean what else besides research, teaching and administration. If you mean what other research, fluid flow in fish noses in general. With over 30,000 species of fish, many of which have different types of nose, there is no shortage of subject matter...