Phoronida
The phylum Phoronida is a small group of marine worms that are characterized by their horseshoe-shaped lophophore, a crown of tentacles used for filter feeding. They are sedentary animals that live in tubes they secrete, often in shallow coastal waters. Phoronids are closely related to brachiopods and bryozoans, and together they form the lophotrochozoan clade.
Common Names
Phoronids are commonly referred to as "horseshoe worms" due to their distinctive horseshoe-shaped lophophore. Other names include "phoronid worms" and "tube worms," although the latter term is also used for other worm-like animals that live in tubes.
Characteristics
Phoronids possess several unique characteristics, including:
- Horseshoe-shaped lophophore: This feeding structure consists of a ring of tentacles that surround the mouth and are used to filter food particles from the water.
- U-shaped gut: The digestive system is bent into a U-shape, with the mouth and anus located near each other.
- Sedentary lifestyle: Phoronids are sessile, meaning they are attached to a substrate and do not move freely.
- Tube dwelling: They live in tubes that they secrete from their body wall, providing protection and a stable environment.
- Dioecious reproduction: Phoronids are sexually dimorphic, with separate male and female individuals.
Environments
Phoronids are found in a variety of marine environments, typically in shallow coastal waters. They are often found attached to rocks, shells, or other hard substrates. Some species live in mud or sand, while others may be found in deeper waters, up to several hundred meters below the surface.
References
For further information on Phoronida, please refer to these reliable sources: