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| The bobbit worm's pincers are horizontal below its antennae. Jenny Huang, CC by 2.0 (adjusted). |
One of the creepiest denizens of the seabed is the bobbit worm, named after the somewhat infamous couple, who—after the husband mistreated his wife—she taught him a rather severe lesson, and by her actions coined the word “Bobbittize”. This just adds to the horror of this worm’s terrifying appearance.
This bristle worm digs a tunnel down into the sand that’s long enough to comfortably fit its body with its hard exoskeleton, which can get up to nearly ten-feet (3 m) in length, although most are about three-feet long (1 m), with a diameter of one inch (2.5 cm).
They have two eyes, but are practically blind, so it uses its five antennae to sense its surroundings. During the day, with just its antennae and two pairs of pincers—retractable mandibles—poking out of its burrow, it waits for an unsuspecting fish, shrimp, snail, sea star, or worm to cruise by, or anything else edible that’s the appropriate size. The antennae move like worms, attracting prey. At night it extends a bit of its body out of the burrow and actively hunts.
When the prey gets close enough, with lightning-fast speed it extends up like a jack-in-the-box and seizes its prey with its sharp pincers, sometimes so strongly that it cuts its victim in half. When the prey remains intact, it injects venom through its teeth that stuns the prey, preventing it from struggling. Then it drags the victim down into its mucus-coated L-shaped burrow. Still, the victim can struggle enough to collapse the burrow’s entrance.
But in spite of all this, these worms aren’t carnivores—they’re omnivores—and they can live on seaweed, or algae and detritus they filter out of the water, or they will scavenge. If they feel threatened, they split themselves into a number of segments, each of which can regrow into a full worm. This is also one of the ways they reproduce, so they don’t mind.
When one of a shoal of fish, such as a bream, spots the worm’s antennae or if one is attacked, it swims vertically above the worm and spits streams of water at it, making the worm retract. Other fish—sometimes including fish of different species—may also join in, firing jets of water at the burrow. This makes them aware of the worm’s location, and might mark the burrow as a danger spot. It’s usually the juvenile breams that do this, not the adults, as they’re a bit more solitary, so it might be an educational lesson for the young.
Such mobbing behavior where prey team up to launch a coordinated attack against a predator is usually seen in birds, but also in some bovines, meerkats, ground squirrels, bees, ants, and freshwater bream called bluegills, which mob turtles, partly to drive them away from their nesting colonies. Humpback whales also mob orcas.
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