Echiurans: Echiura

Physical characteristics: The female has an egg- or sausage-shaped body measuring up to 5.9 inches (15 centimeters) long. The proboscis is long and notched at the tip and reaches up to 4.9 feet (1.5 meters). The body is dark green. Green bonellia have one pair of hooks underneath the body. The flattened, colorless males are much smaller (0.039 to 0.11 inches; 1 to 3 millimeters) and do not have a proboscis, mouth, anus, or circulatory system. Their body is made up almost entirely of reproductive organs.

Geographic range: Green bonellia are found in the northeastern Atlantic Ocean, the Mediterranean and Red seas, and the Indopacific region.

Habitat: Females live in burrows built by other animals in coarse sand, rocks, or spaces between rocks. They are found at depths of 33 to 328 feet (10 to 100 meters). They often have a variety of Green bonellia eat bits of plants, animals, and microscopic organisms found at the base of plants or in sand between rocks. (Illustration by Bruce Worden. Reproduced by permission.) commensals that live with them. The male lives inside the female's body, like a parasite (PAIR-uh-site).

Diet: Green bonellia eat bits of plants, animals, and microscopic organisms found at the base of plants or in sand between rocks. Males rely on females to provide food for them.

Behavior and reproduction: Females move back and forth in their burrows with the help of their proboscis. Muscular contractions of the body wall bring fresh water in contact with the body to renew the supply of oxygen.

Sexes are separate. Fertilization occurs in the genital sac, where a male often lives. The larvae are free swimming. If the larva settles on ocean floor, it develops into a 3.9-inch (10-centimeter) long female. If the larva settles on a female's body (particularly its proboscis), it develops into a 0.039 to 0.078 inch (1 to 2 millimeter) long adult male in about 1 or 2 weeks. Males live as parasites inside the female and produce a ready supply of sperm.

Green bonellias and people: The skin-coloring chemical bonellin is of interest to scientists because it kills many different kinds of organisms, including bacteria.

Conservation status: Green bonellias are not considered endangered or threatened. ∎