Friday October 21, 2022
Science Alert —
Imagine you’re a big yellowfin tuna, miles from shore out in the blue, swimming around carefree, until you start to feel a little itch near your eye. Maybe it’s just a scratch that’s healing, or maybe it’s a tiny crustacean nibbling into your skin.
What do you do? You don’t have hands to pick it off. You don’t have cleaner wrasses nearby to carefully pluck it off for you like you might on a coral reef.
While poring over thousands of hours of video showing the denizens of the open ocean going about their lives, we discovered how tunas and other fishes solve this problem. The answer might be the last thing you’d think of: sharks.
Big fish prefer rubbing shoulders with sharks
In new research published in PLOS One, we found fishes living in the open ocean, like tunas, use sharks to scratch against.
The scratching is likely to remove parasites, dead skin, and other irritants. These fishes are hosts to a diverse array of parasites, but their environment provides them few options for removal.