Meet the tapeworm hunters scouring shark guts for these 'beautiful little' parasites

Hunting for the tapeworms that infest shark and ray guts has made Kirsten Jensen and Janine Caira pros at dissecting on the fly. The two parasitologists have extracted fish entrails in parking lots, on moving boats, and on hotel room balconies. They have to act quickly, because tapeworms don’t survive for long in the bowels of a dead host. Wait too long and “the worms tend to rot because they’re delicate little creatures,” Caira says. “Tiny, delicate, beautiful little creatures.”

Tapeworms are bizarre parasites that latch onto the lining of animals’ guts — yeah, yours, too — and soak up the nutrients floating by. With no heads and no intestines of their own, these living noodles can stretch from a hundredth of an inch to 100 feet in length. For nearly a decade, Jensen at the University of Kansas and Caira at the University of Connecticut have spearheaded an international effort to inventory all of the tapeworms on Earth. Now, the team has reported on nearly 5,000 species of tapeworm in a massive paper published by the University of Kansas Museum of Natural History, including 215 species that are newly discovered.

The project began as part of a larger push by the National Science Foundation to survey the planet’s biodiversity — particularly for less-loved creatures. It’s important work, because tapeworms are the nightmare versions of canaries in the coal mine. These parasites travel up the food chain as they mature: in the ocean, for instance, tapeworm eggs are slurped up by tiny crustaceans, which then get eaten by bigger creatures, like fish. The tapeworm larvae develop in this new host until a larger animal, like a shark, eats it. And that’s how full-grown tapeworms end up in the guts of sharks. It’s the circle of life. So the presence of adult tapeworms in an ecosystem means that the food chain is healthy and intact (if gross).

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