Anoplans and Enoplans: Nemertea
ANOPLANS AND ENOPLANS: NemerteaNO COMMON NAME (Oerstedia dorsalis): SPECIES ACCOUNT
Anoplans (an-OH-pluhns) and enoplans (en-OH-pluhns), also called ribbon worms, have an extremely long snout. The main difference between anoplans and enoplans is that enoplans have a sharp, needlelike structure at the tip of their snout. Anoplans have separate openings for the mouth and snout, but enoplans have one opening for both. Many anoplans are colorful, but most enoplans are drab. Most anoplans and enoplans have toxic substances in their bodies that protect them from predators. Anoplans are several feet (meters) long, the longest growing to 98 feet (30 meters). Most enoplans are about 0.4 inch (1 centimeter) to 4 inches (10 centimeters) long.
Anoplans and enoplans live all over the world.
Most anoplans and enoplans live in the sea near shore— anoplans on soft bottoms and enoplans among algae. Algae (AL-jee) are plantlike growths that live in water and have no true roots, stems, or leaves. Some species live in deep, open water. A few species live in freshwater or on land. The land-dwelling species usually live on tropical islands in damp places under rocks and in rotting wood.
Anoplans eat worms, mollusks, crustaceans, and insect larvae. Mollusks (MAH-lusks) are animals with a soft, unsegmented body that may or may not have a shell. Crustaceans (krus-TAY-shuns) are water-dwelling animals that have jointed legs and a hard shell but no backbone. Larvae (LAR-vee) are animals in an early stage that change form before becoming adults.
BEHAVIOR AND REPRODUCTION
Most anoplans and enoplans live alone. They glide with the help of hairlike fibers on their belly and mucus they produce. Some species swim with wavy movements, but only for a short time. Most anoplans and enoplans have separate sexes. They reproduce by releasing their eggs and sperm into the water. Fertilization (FUR-teh-lih-ZAY-shun), or the joining of egg and sperm to start development, takes place and larvae develop outside the body. In some species fertilized (FUR-teh-lyzed) eggs are deposited in a jelly-like cocoon in which the larvae develop. In a few species eggs are fertilized inside the female, and the young are born looking like small adults rather than as larvae.
ANOPLANS, ENOPLANS, AND PEOPLE
Some of the toxins made by anoplans and enoplans have been studied for use in drugs that help the memory of people with Alzheimer's disease.
WORMS IN A BUCKET
An easy way to collect anoplans and enoplans is to place seaweed and smaller algae in a bucket of seawater. In a few hours to a couple of days any worms in the seaweed will crawl to the sides of the bucket and be easy to see.
WRESTLING FOR DINNER
When prey, such as a crab, comes along, an enoplan hiding in the sand sticks out its long snout, rapidly wraps it around the crab, and injects immobilizing toxins and digestive enzymes into the prey. When the crab stops struggling, the worm pulls in its snout, comes out of its hole, and enters the prey, whose tissues are drained from the shell in about an hour.
The World Conservation Union (IUCN) lists two species of anoplans and enoplans as Vulnerable and one as Lower Risk/Near Threatened. Vulnerable means facing high risk of extinction in the wild. Low Risk/Near Threatened means at risk of becoming threatened with extinction in the future.
Physical characteristics: Oerstedia dorsalis worms are 0.4 to 0.6 inch (10 to 15 millimeters) long and 0.04 to 0.08 inch (1 to 2 millimeters) wide. They have four eyes. Most of these worms are brown to reddish brown and have a white stripe on the back. Some have light or dark brown speckles; some have yellowish dots; some are cream colored without spots; and some have dark bands on a light background. The belly usually is paler than the back.
Habitat: O. dorsalis worms live in the sea close to shore. They usually live among algae.
Diet: O. dorsalis worms eat small crustaceans and worms.
Behavior and reproduction: Scientists do not know how O. dorsalis worms behave. The sexes are separate. Fertilization takes place outside the body after the worms release eggs and sperm into the water.
Oerstedia dorsalis and people: O. dorsalis worms have no known importance to people.
Conservation status: O. dorsalis worms are not considered threatened or endangered. ∎
FOR MORE INFORMATION
Carson, Rachel. The Edge of the Sea. 1955. Reprint, Boston: Mariner, 1998.
Niesen, Thomas M. The Marine Biology Coloring Book. 2nd ed. New York: HarperResource, 2000.
Shimek, Ronald L. "Tie A Yellow Ribbon (Worm) around the Old Reef Rock." Reefkeeping.http://www.reefkeeping.com/issues/2004-01/rs/ (accessed on February 9, 2005).