Urechis

Urechis is a genus of spoon worms in the family Echiuridae, within the phylum Annelida. These marine, wormlike animals are natural burrowers of soft sediments in shallow coastal waters and are found in temperate to tropical regions around the world. The body is elongated and soft, with the anterior region bearing a large, spoon-shaped proboscis used for feeding, and the posterior region forming a relatively simple, unsegmented trunk. They lack the paired bristles (chaetae) that characterize many other annelids.

Ecology and morphology: Urechis species live in U-shaped or straight burrows lined with mucus in mud or sand. The burrow system often has two openings, and the animal can extend its proboscis into the water to capture organic particles. Feeding is primarily detritivorous and suspension-based, relying on mucus nets and ciliated surfaces to trap and ingest microorganisms and particulate matter from the surrounding water.

Distribution and species: The genus includes several described species with regional distributions. Notable examples are Urechis caupo on the Pacific coast of North America and Urechis unicinctus in East Asia. Other species occur in various marine habitats across oceans, reflecting a broad, though regionally diverse, distribution.

Reproduction and development: Urechis species are typically dioecious, releasing eggs and sperm into the water for external fertilization. The resulting free-swimming larvae undergo development characteristic of annelids before settling to form burrows.

Human interactions: Some species, particularly Urechis unicinctus, are harvested as seafood in East Asia and are consumed in various preparations, sometimes as raw or lightly processed delicacies. The worms are also used as bait in some fishing contexts.