Urechis
Urechis is a genus of marine spoon worms in the family Urechidae. These burrowing invertebrates are commonly known as “fat innkeeper worms“, “penis worms“, or “sea potatoes“, due to their distinctive cylindrical shape and fleshy appearance. Their range extends from the Pacific coast of North America to East Asia.
Characteristics
Urechis species are characterized by their elongated, sausage-shaped bodies, which lack any appendages or external segmentation. They typically range in size from 10 to 20 centimeters in length, and their bodies are covered in a thin, slimy cuticle. They possess a prominent proboscis, a fleshy, retractable structure used for burrowing and feeding. Their digestive system is looped, with the anus located near the mouth. They also possess a unique pair of nephridia, which function as excretory organs.
Habitat and Ecology
Urechis species are burrowing invertebrates found in intertidal and subtidal zones along sandy or muddy bottoms. They create distinctive U-shaped burrows in the sediment, which they use for feeding and protection. They are deposit feeders, consuming sediment and organic matter. Their burrows can also provide shelter for other marine organisms, earning them the nickname "fat innkeeper worms".
Reproduction
Urechis worms are dioecious, meaning they have separate sexes. Reproduction involves external fertilization, with the release of sperm and eggs into the water. The fertilized eggs develop into planktonic larvae, which eventually settle to the bottom and burrow into the sediment.
Species
The genus Urechis currently includes three recognized species:
- Urechis caupo (The most common species found along the Pacific coast of North America)
- Urechis unicinctus (Found in East Asia)
- Urechis novaezealandiae (Found in New Zealand)
Importance
Urechis worms play an important role in marine ecosystems. Their burrowing activities help to aerate the sediment and enhance nutrient cycling. They are also an important food source for a variety of marine animals, including fish, crabs, and birds. Additionally, in some cultures, Urechis species are considered a delicacy.
References
World Register of Marine Species
A molecular phylogeny of the echiuran worm genus Urechis