Beard Worms: Pogonophora

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BEARD WORMS: Pogonophora

NORWEGIAN TUBEWORM (Siboglinum fiordicum): SPECIES ACCOUNT

PHYSICAL CHARACTERISTICS

Beard worms live in tubes made out of chitin (KYE-tehn) and protein. Chitin is a substance similar to fingernails that makes up the outer skeleton of some animals. The tubes are mostly below the surface of the ocean bottom, with just the upper end exposed. The yellowish, brownish, or black tubes are not branched. They are sometimes distinctly fringed, flared, segmented, or have a ringed pattern.

Most beard worm species are 3.94 to 29.53 inches (100 to 750 millimeters) in length, but are less than 0.039 inches (1 millimeter) thick. Their bodies have up to 200 tentacles on the head region. Each tentacle has tiny branches. The long, slender body trunk is followed by a small, segmented tail. The body is covered with a flexible, skinlike cuticle (KYU-tih-kuhl) that is covered with thick parts that create various patterns. Cuticle, unlike skin, is a body covering that is not made up of individual cells. Some beard worms have a collarlike ridge that rests on the rim of the tube when the worm's body is extended beyond the tube opening.

The nervous system includes a mass of nerves toward the head, a nerve cord running along the underside of the body, and a network of small nerve fibers. All of these are completely inside the skin. Under the skin is a thick layer of muscles that runs along the length of the body. The coelom (SIGH-lum), or main body cavity, is made up of a small cavity in the head region that connects to cavities inside each of the tentacles. A pair of cavities is found inside the body trunk. The segments of the tail also have a series of cavities inside, each separated by a layer of muscles.

Adults do not have a mouth or digestive system. Instead, they absorb bits of food from the water and mud directly through their tentacles and body trunk. They also have special tissues on their body trunk that contain bacteria that help to process food. The circulatory system is made up of parallel blood vessels along both their upper and undersides that run nearly the entire length of the body. The circulatory system is closed, with blood moving throughout the body inside the vessels.

GEOGRAPHIC RANGE

Beard worms live on the bottom of the Norwegian fjords and in the Atlantic, Caribbean, Pacific, Indian, Arctic, and Antarctic oceans.

HABITAT

Beard worms live on the ocean floor on continental slopes and in deep ocean trenches. Some species are found only on decaying wood near deep sea geysers at depths of 328 to 32,808 feet (100 to 10,000 meters). These deep sea geysers are called hydrothermal vents.

DIET

Most organisms depend on sunlight to produce or acquire food. The conversion of sunlight to simple sugars and other compounds that can be used as food is called photosynthesis (FO-to-SIN-thuh-sihs). Beard worms, especially those living in total darkness, must rely on billions of bacteria living in them to make food. The worms provide the bacteria with carbon dioxide produced by their own bodies and hydrogen sulfide collected from water coming through the hydrothermal vents. As the bacteria convert these chemicals into energy for themselves, they produce simple sugars and other compounds that the worms can absorb as food. The conversion of chemical reactions into food is called chemosynthesis (KEY-moh-SIN-thuh-sihs).

BEHAVIOR AND REPRODUCTION

The tentacles of the beard worm are extended from their tube opening, but the worms can withdraw quickly into their tubes when threatened by crabs or other predators.

Males and females must mate to reproduce. The males of some species release sperm packets into the water. They eventually settle on or near the tube openings of female worms. The packets break down, and sperm is released. The sperm find their way into the reproductive ducts of the females, and the eggs are fertilized inside their bodies. The eggs apparently develop inside the tube. The larvae (LAR-vee), or early stage of the animal, are free-swimming, but eventually settle into the mud and begin producing their own tubes and acquiring bacteria.

BEARD WORMS AND PEOPLE

Beard worms are of great scientific interest because some species live in extreme environments.

STAY TUNED!

The classification of beard worms has been debated by scientists for years. Although treated here as a separate phylum, many scientists consider them to be a group within the phylum Annelida. Certain physical features, plus analysis of their DNA, support this relationship. Some scientists, however, consider beard worms a specialized group. Views of their relationships will continue to change as scientists learn more about these unusual sea creatures.

CONSERVATION STATUS

No beard worms are considered endangered or threatened.

NORWEGIAN TUBEWORM (Siboglinum fiordicum): SPECIES ACCOUNT

Physical characteristics: The body of a Norwegian tubeworm grows up to 11.8 inches (300 millimeters) in length and 0.009 inches (0.25 millimeters) thick. The smooth tube is patterned with gray or brown rings. This tubeworm has only one tentacle.

Geographic range: The Norwegian tubeworm lives only in Norway.

Habitat: Norwegian tubeworms live on the sandy or muddy bottoms of fjords, at depths ranging from 82 to 656.7 feet (25 to 200 meters).

Diet: The Norwegian tubeworm relies mostly on bacteria to produce food.

Behavior and reproduction: This worm uses its tail to burrow into the mud or sand.

Norwegian tubeworms and people: Norwegian tubeworms are one of the most easily studied beard worms because they live at relatively shallow depths.

Conservation status: The Norwegian tubeworm is not considered endangered or threatened. ∎

FOR MORE INFORMATION

Books:

Desbruyéres, D., and M. Segonzac, eds. Handbook of Deep-Sea Hydrothermal Vent Fauna. Brest, France: IFREMER, 1997.

Van Dover, C. L. The Ecology of Deep-Sea Hydrothermal Vents. Princeton, NJ: Princeton University Press, 2000.

Periodicals:

McMullin, E. R., S. Hourdez, S. W. Schaeffer, and C. R. Fisher. "Phylogeny and Biogeography of Deep Sea Vestimentiferan Tubeworms and Their Bacterial Symbionts." Symbiosis 34 (2003): 1-41.