Marine Worms

From leeches to peanut worms to bristle worms, marine worms are some of the most unique worm species on the planet. After all, they need more than the earth’s rich soil to survive – they need water! The water, however, must be mixed sand or soil to create a nice “muddy” space for the worm to inhabit. Marine worms come in a variety of shapes and sizes. They may be long and thin, plumb and short, flattened and floppy, bright and colorful or dull and dark.

Marine worms are grouped in many different categories or “phyla” ranging from annelids to sipunculids (Sipuncula). Some marine worms live underneath boulders and rocks in the sea while others burrow underneath rocks and boulders in mud or sand. Marine worms include but are not limited to: peanut worms, ribbon worms, flatworms, ringed or segmented worms, tube-making worms, and burrow-dwelling worms. Continue reading to learn more about several marine worm species and where to find them.

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About Peanut Worms

There are an estimated 300 to 500 species of peanut worms in existence today. A peanut worm, phylum Sipuncula, is shaped like a cylinder or peanut, but it still has worm-like movements and habits. Much like earthworms, peanut worms prefer to live in moist, dark places. Many peanut worms burrow themselves under rocks and boulders that can be found in the mud or sand or they make their home in reef.

The peanut worm has a fat, round section that grows into a long, retractable head extension with a mouth at the end (proboscis). The section has the ability to turn inside out. The peanut worms body is tan or brownish in color with black rings on the proboscis and black blotches on the body.

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Unlike other types of worms like apple tree worms, which actually eat apples, and pecan tree worms, that actually eat holes in pecans, peanut worms do not eat peanuts. They eat organic matter found in their favorite places to be – the sand and mud.

Ribbon Worm

The ribbon worm, also called proboscis worm, bootlace worm, nemertean, or nemertine, is any member of the phylum Nemertea. Nemertea is also called Nemertinea or Rhynchocoela. There are more than 900 Nemertea species, including free-living forms as well as parasites of sea squirts, crustaceans, and mollusks. Most Nemertea are found in marine habitats, but some may live on land (terrestrial) or in freshwater.

There are 13 known terrestrial ribbon worm species recorded worldwide. Four exist in Australia (Argonemertes: australiensis; dendyi; hillii; stocki) and they are from the Argonemertes genus. Land-dwelling nemerteans need dark, damp, and cool habitats to live. They can be found under rotting logs, in leaf litter or under large rocks or stones. They are typically found in lands where the climate is calm and damp

Ribbon worms have muscular eversible (able to be turned inside out) proboscis (tubular feeding and sucking organ), housed in a fluid-filled enclosure above the belly or gut. This area is used to trap prey and it is used for burrowing. Land-dwelling ribbon worms may use it for fast movement. At a minimum of 8 inches long, the ribbon worms body is long and lean with finlike appendages. Some giant ribbon worm species or ‘Lineus longissimus’ may reach up to 100 feet long.

Ribbon worms reproduce annually. Fertilization occurs externally, and the eggs and sperm are released separately. Ribbon worms develop by either the direct method or ciliated larval stage. The direct method does not include a larval stage and the ciliated larval stage is either a free-swimming larva called the pilidum or the Desor’s larva, which is similar to an adult. The larvae transform into ribbon worms in several days to several weeks after swimming among plankton.

Ribbon worms have several unique abilities and traits. Some may have separate male and female organs (dioecious) while others may have both male and female organs (hermaphroditic). Ribbon worms can regenerate chopped or damaged parts of their body. In fact, ribbon worms may break up into pieces on their own and the pieces will grow into new worms.

According to Encyclopedia Britannica,, “in general, the ribbon worms are regarded as a distinct phylum at the highest point of acoelomate (without a body cavity) development; however, some evidence suggests that one proboscis cavity, or rhynchocoel, may be a true coelom. The important features used to classify the ribbon worms include the position of the brain relative to the mouth, the presence or absence of a stylet (or stylets) on the proboscis, and the position of the lateral nerves relative to the muscle layers.

For pictures or video of the giant ribbon worm or an average size ribbon worm in action, visit: or

1 Comment

  1. Don Geiszler

    I was recently shown a picture of what were called sand worms.I was told that they live under the rocks that are close to the shore.The picture was in color and they appeared to be similar in color to earth worms.I was told that they have pincers that can inflict pain.What are they and does one have to dig them or do they just reside on top of the sand and under the rocks?

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