Other Free Encyclopedias » Animal Life Resource » Mollusks, Crustaceans, and Related Species » Echiurans: Echiura - Physical Characteristics, Habitat, Behavior And Reproduction, Echiurans And People, Green Bonellia (bonellia Viridis): Species Account - GEOGRAPHIC RANGE, DIET, CONSERVATION STATUS

Echiurans: Echiura - Physical Characteristics

body proboscis trunk reach

Echiurans (eh-key-YUR-enz) are sea creatures sometimes known as spoon worms or fat innkeepers. They have bilateral symmetry (bye-LAT-er-uhl SIH-muh-tree) and can only be divided into similar halves along one plane. Their sausage-shaped bodies are soft, unsegmented, and have two distinct regions, the proboscis and body trunk. The proboscis (pruh-BAH-suhs) is a long, flexible, tubelike snout. The trunk may reach 15.75 inches (40 centimeters) in length, but the proboscis is much longer and can reach up to 3.28 to 6.56 feet (1 to 2 meters). The flexible and muscular proboscis is used to gather food. The lower surface is covered with hairlike cilia (SIH-lee-uh) that help move food toward the mouth located at the base of the proboscis. The proboscis can be extended or retracted, but not withdrawn inside the trunk. It is usually white, pink, green, or brown and can be short or long, scoop- or ribbonlike, and flat or fleshy and spoonlike. The tip may be squared off or notched.

The surface of the thick body trunk is smooth or rough and is gray, dark green, brown, pinkish, or reddish in color. Most species have a pair of hooks on the underside of the body, near the front of the trunk. Some also have one or two rings of bristles around the anus (AY-nuhs), or the opening of the digestive tract at the end of the body. The body wall is wrapped in layers of muscles that run around the body, along its length, or at an angle different from the other muscle groups. The body is supported from the inside by a large, fluid-filled body cavity, or coelom (SIGH-lum). A closed circulatory system may or may not be present. Pairs of kidneylike organs remove wastes from the body's fluid and expel waste from the body.


Echiurans: Echiura - Habitat [next]

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