Phylum Phoronida: The Horseshoe Worms (And a Summary of Lophophorata)
Lophophorata and Phoronida Overview
This section provides an in-depth look at the phylum Phoronida, focusing on their anatomy, physiology, reproduction, and unique characteristics within the clade Lophophorata.
Anatomy and Physiology of Phoronida
- Phoronida filter-feed using a lophophore, living in tough chitinous tubes. Their body wall includes a cuticle, epidermis, and muscular system. An ampulla at the bottom end anchors them in the tube.
- The lophophore of Phoronida has two parallel ridges forming a horse-shoe shape for feeding. Their gut runs from mouth to stomach to intestine and ends at the anus located outside the lophophore.
Respiration and Circulatory System
- Due to residing in oxygen-deprived sediment, Phoronida use their lophophores for gas exchange as well as respiration. They lack a heart but have a circulatory system with hemoglobin-containing blood cells.
- Oxygenated blood is carried away from the lophophore through contraction of major blood vessels. Nervous system components include nerve rings and plexus. Most are monoecious with some capable of asexual reproduction.
Reproduction and Larval Development
- Phoronida reproduce sexually by releasing gametes during breeding season for fertilization. Eggs are brooded internally until hatching into free-swimming actinotroch larvae that undergo metamorphosis into adults after about twenty days.
Comparative Analysis of Lophophorata Phyla
This segment offers a comparative review of the four phyla within Lophophorata concerning coelom presence, support structures, tentacle characteristics, colonial behavior, feeding mechanisms, and concludes our study on Lopohoratans.
Comparative Analysis
- All four phyla possess a coelom except Entoprocta. Support structures vary from erect tubes in phoronida to valves in brachiopoda to mineralized forms in bryozoans while entoproctans lack support.
- Tentacles across phyla are hollow except for Entoprocta. Anus locations differ among species with variations in colonial behavior observed; most bryozoans and entoprocta are colonial while brachiopods are not.