When we think of “worms,” we often picture the brown-pink, slimy earthworm. You know, the ones that emerge in droves after a big rain storm or the ones favored by some anglers.

No offense to earthworms, but their marine cousins are very different from the drab-colored terrestrial version. Today we’re going to dig in (so to speak) on marine worms.

Worms: The Basics

Many of the “worms” we are most familiar with are in the phylum Annelida, also known as segmented worms. There are worms throughout the animal kingdom, including the flatworms in phylum Platyhelminthes, parasitic worms in phylum Nematoda and ribbon worms in phylum  Nemeratea (all delicious topics for another time).

Segmented worms are easily distinguished by their (unsurprisingly) segmented bodies—picture the rings on an earthworm, which show the connection of two segments. There are more than 12,500 species of Aannelid worms, 70% of which are polychaete (pronounced poly-keet) worms.

Almost all of the animals in the class polychaeta are found in the ocean from shallow tide pools to the deep, deep trenches. They have many small bristles and are often also called bristle worms. Many polychaetes will use a long appendage called a proboscis to push aside sand and burrow into sediment to stay safe from predators.

Types of Polychaete Worms

There are a wide variety of polychaetes in our ocean, but there are a few that beach-goers, snorkelers and divers might be familiar with. Here are some examples:

• Bearded fireworms (Hermodice carunculate): Recognized by their bright orange coloring, fireworms are fierce predators of corals and anemones. They are found on reefs and in seagrass beds throughout the tropical Atlantic, Gulf of Mexico, Caribbean and Mediterranean. Their bristles, also known as chaeta, are packed with venom that is unleased on anyone unlucky enough to come into contact with it. They get their name for the “fiery” burn caused by the toxins.
• Feather duster worms (family Sabellidae): At first glance, feather duster worms don’t look like worms. They look, well, … like feather dusters. These worms build a hard tube around their bodies, made of secreted proteins and sand, that helps protect from predators. Then, they stretch out their feathery tentacles to eat and breathe, allowing the ocean currents to bring them the resources they need. If threatened, the worm will quickly retract the tentacles to the safety of the tube.
• Riftia tubeworms (Riftia pachyptila): Found in the deep sea, these worms are among the few species that can survive near harsh hydrothermal vents. These worms can grow to eight feet long and have a symbiotic relationship with the chemosynthetic bacteria. The tube worm absorbs oxygen and hydrogen sulfide through its bright red appendage called a plume, which the bacteria then use in the process of chemosynthesis. In turn, the worm receives energy from the bacteria.

Polychaete worms are some of the most abundant, yet underappreciated, animals in the sea. And with 80% of the ocean yet to be explored, there are certainly more to be discovered.

Can’t get enough weird and wonderful ocean critters? Check out the tongue-eating louse, the flamingo-tongue snail and the hagfish. Then, head to Ocean Conservancy’s Action Center to help protect these incredible animals and the ocean they depend on.