The reproductive strategy, called broadcast spawning, is found here and there throughout the animal kingdom. Corals (cnideria) and abalone (mollusca) are also examples. Spawning for Chaetoptera begins when worms eject either eggs or sperm, which meet up and become fertilized in the water column. When a worm ejects male or female gametes, neighboring worms are triggered to follow suit. The strategy’s success is attributed to the close-knit community tube worms subscribe. The clusters of tubes can measure tens to hundreds of feet across.
Group living is a relative concept for Chaetoptera because each lives singly in a rigid, U-shaped tube composed of parchment-like material mixed with sand grains. Since the body is too fragile to survive outside the tube, the critter is invisible to divers. Worms that might be curious about the outside world can’t leave anyway since the body is anchored to the tube’s interior, and the two potential exits are too narrow for the animal to squeeze through. Growth, then, would seem to pose a predicament to an animal stuck in a leathery tube but the worm has it figured out. Chaetoptera belong to the family of polychaete (bristle) worms, and they do in fact have bristles (chaetae). The chaetae are employed to make slices on the tube to stretch it out. At the same time, material is secreted to fill in the cracks. Voila, the tube is made wider, and its integrity is maintained.
Eating is a sticky affair for these worms. Let’s just say they aren’t called mucus-bag feeders for no reason. As they fan water through their tube with three pistonlike segments, two wing-like legs simultaneously hold the mucus bag across the current to filter the water. Once the bag is clogged (around five minutes) with tiny algal and mud particles, they eat the bag, then secrete a new one. The mucus traps minuscule organisms, which the worm eats wrapped in its own spit.
There is yet another interesting development surrounding these worms. They are bioluminescent. Why a housebound, hermit worm needs light is unknown but presently under study. That will be a story for another day.
— Judith Lea Garfield, naturalist and underwater photographer, has authored two natural history books about the underwater park off La Jolla Cove and La Jolla Shores. Send comments to firstname.lastname@example.org.