GOTTA SCAN ’EM ALL

An American researcher has embarked on a project to scan the inner structures of every species of fish known to science – all 33,000 of them. Here’s what he’s uncovered

There is a small lab on Friday Harbour, San Juan Island, just off the US state of Washington. Here, marine biologist Adam Summers spends much of his time painstakingly loading fish after fish into a CT scanner to produce detailed images that reveal their intricate skeletons and inner structures. The project began inauspiciously several years ago when Summers would pay covert night-time visits to local hospitals, begging to use their CT scanners during periods of downtime. “We would stuff dead sharks and rays and things into bags, so nobody could tell what they were,” he says.

After amassing a library of several successful scans, he began sharing his results on Twitter. To his surprise he got a huge response, with many biologists asking him to scan their favourite fish. “I jokingly replied that I was going to #ScanAllFish,” he says. At the time, he didn’t really believe that would happen because it was taking 12 hours to scan three or four fish, and there are more than 33,000 species to get through. But with the current total of scans standing at 3,827 he reckons the project could be completed in as little as two years, though they may have to skip a few of the biggest, rarest fish.

Thanks to the success of his images, Summer applied for a grant for his own CT scanner, which has been installed in his labs. Every scan is immediately posted online for anyone to use, with Summers not asking for any credit. The project has already racked up more than half a million downloads, with everyone from scientists and engineers to artists and teachers using the images. “We’re exposing our data to a world of people who have great brains and will do far better things with it than we ever could,” he says.

Anyone can use the scanner to scan their favourite species, provided they make the data freely available. “If you come to the island you can bring a suitcase full of dead things and CT them,” says Summers. He is also collaborating with museums worldwide to scan their collections. It is hoped that these ‘digital dissections’ will allow people to see inside fish and manipulate them in ways that is just not possible with preserved specimens.

As well as CT scans, Summers also makes fish skeletons visible through their skin using dyes that stain bone red and cartilage blue. He bleaches the fish white with hydrogen peroxide and dissolves its flesh with the digestive enzyme, trypsin, leaving only skin and connective tissue. The fish is then photographed while immersed in glycerine, which renders the unstained parts invisible. 2