Bone-eating worm

Natural history

The bone-eating worm’s body and feeding strategy is very different from those of most animals. This worm has no eyes, legs, mouth, or stomach, but does have colorful feathery plumes and green “roots.” The reddish plumes extend into the water and act as gills. They connect to a muscular trunk, which can be withdrawn into a transparent tube when the worm is disturbed.

At the other end of the trunk, hidden inside the whale bone, the body widens to form a large egg sac. The green roots, branching off from the egg sac, secrete acid into the bone to dissolve it. Symbiotic bacteria then digest the dissolved organic material, providing a food source for the worm.

Conservation

Whale carcasses—or whalefalls—add a massive amount of food to the food-limited environment of the deep sea. One whalefall can provide as much organic material as thousands of years of marine snow, the organic debris that drifts down from surface waters to sustain life in the deep.

Many whale populations are estimated to be only 10 to 25 percent of their historical levels despite the 1982 International Whaling Commission's moratorium on commercial whaling. Fewer whales means fewer whalefalls, and less habitat for whale-fall species such as bone-eating worms.

Cool facts

• Whale skeletons support so much life because they contain an enormous amount of oil. Large whale bones can be more than 60 percent oil by weight. For example, a 90-ton whale is estimated to have 5 tons of oil in its bones—a veritable feast for oil-eating bacteria.
• Scientists who discovered these tube worms were puzzled by the lack of male tube worms until a close examination of female worms revealed microscopic males living within their bodies. They looked as if they had never developed past their larval stage but they contained copious amounts of sperm. As many as 50 to 100 males may reside in one female. Females may continuously recruit new males. MBARI scientist Robert Vrijenhoek said, “These worms appear to be the ecological equivalent of dandelions—a weedy species that grows rapidly, makes lots of eggs and disperses far and wide.”
• After a whale skeleton has been consumed, all the bone-eating worms at that site will die off. Before this happens, they must release enough eggs or larvae so that some tiny proportion will be transported by the ocean currents and survive until they can find and colonize another whale carcass. Adult bone-eating worms will release gametes continuously throughout their lives to ensure the success of their offspring.