Phoronidae
The Phoronidae, commonly known as phoronids or horseshoe worms, are a small group of marine animals. They are sedentary, tube-dwelling worms with a unique horseshoe-shaped lophophore, a crown of tentacles used for filter feeding. Phoronids are found in various marine environments worldwide, often burrowing in sediments, attaching to rocks, or living within crevices.
Characteristics
Phoronids are characterized by their distinctive horseshoe-shaped lophophore, which is used to capture food particles from the water. The lophophore is supported by a series of stiff, chitinous rods called "tentacular supports". The body is covered in a chitinous tube, which the animal secretes. The tube is attached to a base, and the animal can withdraw into the tube for protection. Phoronids are bilaterally symmetrical and possess a digestive system with a mouth and anus located at the top of the lophophore. They are typically small, ranging in size from a few millimeters to several centimeters.
Environments
Phoronids are found in a variety of marine environments, including:
- Intertidal zones
- Subtidal zones
- Coral reefs
- Deep-sea trenches
They often live in areas with high water flow to facilitate filter feeding.
Reproduction
Phoronids are typically hermaphroditic, meaning they possess both male and female reproductive organs. Some species may release sperm and eggs into the water column for external fertilization, while others may internally fertilize eggs within the body. Larvae develop into free-swimming organisms, eventually settling and forming a tube.
References
Wikipedia: Phoronida
World Register of Marine Species: Phoronida
National Center for Biotechnology Information: Phoronida