Marine Worms, Pacific Northwest
There are all kinds of marine worms, some are harmless, some are beautiful and some can sting with powerful toxins.
Phylum platyhelminthes are the flat worms. These are among the simplest of animals, consisting of essentially a flattened tube of muscle and a simple digestive system with a single opening that serves as both mouth and anus. It has no true body cavity, nor does it have the distinct body segments that characterize more complex worms. The vast majority of species in this phylum are parasites.
The ribbon marine worms are slightly more complex. While they also have a flattened shape, they have a one-way digestive system with separate mouth and anus and a simple blood vascular system. Ribbon Worms are carnivores that prowl the bottom for prey.
The annelids are the segmented worms, in other words, made up of segments that are formed by subdivisions that partially transect the body cavity. Also included are the feather duster worms.
The chaetognatha is a relatively unknown group of worms. Chaetognatha are known as arrow worms, they are tiny marine predators that locate their prey by detecting vibrations produced by zooplankton, they use sharp hooks and teeth at the front of the body to grab their victims and immobilize them with neurotoxins.
The horseshoe worms are an exclusively marine group of lophophorate animals, the phoronida are one of the smallest and least familiar of the marine worms, there are about twelve species of these worms.
There are more worms than these but these are the most common worms on our coast, they are all quite fascinating to observe if you take the time to locate them.