There are a lot of strange jobs out there, but "shark-intestine tapeworm hunter" may just take the cake. Parasitologists Kirsten Jensen and Janine Caira have been working on a decade-long project to inventory all the tapeworm species on the planet, according to the Verge. And they do it by dissecting dead sharks.
Why look for tapeworms in sharks?
Jenson and Caira are in charge of finding tapeworms in sharks and rays, but they're part of a larger team that's looking for tapeworms in all different species, including birds, mammals and reptiles.
There is, however, a good reason to look for tapeworms in sharks specifically. As larvae, tapeworms start off by infecting small animals like crustaceans, which slurp up the tapeworm eggs.
When the crustacean is eaten by a fish, the tapeworm has found a new, bigger host where it can grow. This process continues until the adult tapeworm is an home in an apex predator.
Because sharks are at the top of the food chain in many ecosystems, finding a tapeworm in a shark is a sign the the food chain is healthy.
Where do you find specimens?
You don't want to kill a shark just to cut it open to see if it has a tapeworm inside it. But foraging for sharks that died of natural causes isn't a great method either, because tapeworms don't live long after the host dies.
To solve this problem, Jenson and Caira partnered with fishermen. They offered to clean fresh catches in exchange for keeping the shark and ray intestines. Once the intestines were acquired, they dissected them as soon as possible.
Because the pair is traveling all the time, they've had to improvise a lot. They've dissected on boats and in parking lots.
Once, in Vietnam, they brought ray guts back to their hotel room and dissected them on their balcony.
Are tapeworms harmful to sharks?
In humans, tapeworms can cause B-12 deficiency, anemia, intestinal blockage and other problems. But what do they do to sharks?
According to Caira, tapeworms don't cause sharks very much damage. The relationship between tapeworm and shark could be considered commensalism rather than parasitism, but the question of whether true commensalism exists is still up for debate. The tapeworms that live in sharks cannot live in humans.
How many tapeworm species are there?
Jensen and Caira have catalogued 5,000 species of tapeworm, 215 of which were newly discovered. But they said there are probably 20,000 different species out there. Who knew there was so much diversity among terrifying parasites?