What is a ribbon worm?

Ribbon worms are invertebrates belonging to the phylum Nemertea, also called Nemertinea or Rhynchocoela. Most of the approximately 900 species live in marine environments, but some inhabit fresh water or land. Ribbon worms have a circulatory system and a gut with a separate mouth and anus, and they use a muscular, tube-shaped organ called a proboscis to trap prey. Most ribbon worm species have separate sexes, and fertilization occurs externally. They can develop directly or through a ciliated larval stage. All ribbon worms can regenerate lost or damaged body parts, and some reproduce asexually through fragmentation.

Where do ribbon worms live?

Ribbon worms, belonging to the phylum Nemertea, are mostly free-living invertebrates, but some are parasites to crustaceans, mollusks, and sea squirts. The majority of the roughly 900 species live in marine environments, but some can be found in freshwater or on land. They are also called proboscis worms because of their muscular, eversible proboscis, which is a tube-shaped organ that can be used to trap prey or for burrowing.

What does a ribbon worm look like?

Ribbon worms, from the phylum Nemertea, exhibit a diverse array of appearances. While most are less than 20 cm (8 inches) in length, some species, like Lineus longissimus , can reach up to 30 m (100 feet). Their bodies are typically long and slender, capable of significant extension during movement. Though often uniformly colored, many species boast vivid patterns including stripes, bands, speckles, or geometric shapes. Some ribbon worm species that swim in deep water have flat, broad bodies with fin-like appendages. These invertebrates possess a unique proboscis, a muscular, tube-shaped organ often equipped with a needle-like stylet used for trapping prey or burrowing. They are the simplest animals to have a circulatory system and a complete digestive system with a separate mouth and anus.

How do ribbon worms move and eat?

Ribbon worms, belonging to the phylum Nemertea, move using a long, slender body that extends during movement. Some land-dwelling species use their stylet for rapid movement. To eat, ribbon worms use a unique tube-shaped organ called a proboscis, which is housed in a fluid-filled chamber above the gut. Many aquatic species possess a needle-like stylet on the proboscis to trap prey. The stylet can also be used for burrowing.

What do ribbon worms use their proboscis for?

Ribbon worms, belonging to the phylum Nemertea, utilize a muscular, eversible proboscis, housed in a fluid-filled chamber, for several key functions. The primary use of this tube-shaped organ is to trap prey, and in many aquatic species, the proboscis includes a needlelike stylet to aid in prey capture. Additionally, the stylet can be employed for burrowing. In land-dwelling ribbon worms, the proboscis is used for rapid movement.

ribbon worm

Introduction References & Edit History Quick Facts & Related Topics

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Also called:: bootlace worm, proboscis worm, nemertine, or nemertean

Related Topics:: Prostoma; Geonemertes; Lineus longissimus; Eumetazoa

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ribbon worm

invertebrate

Also known as: Nemertea, Nemertinea, Rhynchocoela, bootlace worm, nemertean, nemertine, proboscis worm(Show More)

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What is a ribbon worm?
Ribbon worms are invertebrates belonging to the phylum Nemertea, also called Nemertinea or Rhynchocoela. Most of the approximately 900 species live in marine environments, but some inhabit fresh water or land. Ribbon worms have a circulatory system and a gut with a separate mouth and anus, and they use a muscular, tube-shaped organ called a proboscis to trap prey.

Most ribbon worm species have separate sexes, and fertilization occurs externally. They can develop directly or through a ciliated larval stage. All ribbon worms can regenerate lost or damaged body parts, and some reproduce asexually through fragmentation.
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Where do ribbon worms live?
Ribbon worms, belonging to the phylum Nemertea, are mostly free-living invertebrates, but some are parasites to crustaceans, mollusks, and sea squirts. The majority of the roughly 900 species live in marine environments, but some can be found in freshwater or on land. They are also called proboscis worms because of their muscular, eversible proboscis, which is a tube-shaped organ that can be used to trap prey or for burrowing.
1 Britannica Source
1. ribbon worm
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What does a ribbon worm look like?
Ribbon worms, from the phylum Nemertea, exhibit a diverse array of appearances. While most are less than 20 cm (8 inches) in length, some species, like Lineus longissimus, can reach up to 30 m (100 feet). Their bodies are typically long and slender, capable of significant extension during movement. Though often uniformly colored, many species boast vivid patterns including stripes, bands, speckles, or geometric shapes. Some ribbon worm species that swim in deep water have flat, broad bodies with fin-like appendages.

These invertebrates possess a unique proboscis, a muscular, tube-shaped organ often equipped with a needle-like stylet used for trapping prey or burrowing. They are the simplest animals to have a circulatory system and a complete digestive system with a separate mouth and anus.
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2. ribbon worm
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How do ribbon worms move and eat?
Ribbon worms, belonging to the phylum Nemertea, move using a long, slender body that extends during movement. Some land-dwelling species use their stylet for rapid movement.

To eat, ribbon worms use a unique tube-shaped organ called a proboscis, which is housed in a fluid-filled chamber above the gut. Many aquatic species possess a needle-like stylet on the proboscis to trap prey. The stylet can also be used for burrowing.
1 Britannica Source
1. ribbon worm
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What do ribbon worms use their proboscis for?
Ribbon worms, belonging to the phylum Nemertea, utilize a muscular, eversible proboscis, housed in a fluid-filled chamber, for several key functions. The primary use of this tube-shaped organ is to trap prey, and in many aquatic species, the proboscis includes a needlelike stylet to aid in prey capture. Additionally, the stylet can be employed for burrowing. In land-dwelling ribbon worms, the proboscis is used for rapid movement.
1 Britannica Source
1. ribbon worm
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

ribbon worm, any member of the invertebrate phylum Nemertea (sometimes called Nemertinea, or Rhynchocoela), which includes mainly free-living forms but also a few parasites of crustaceans, mollusks, and sea squirts. The majority of the approximately 900 known nemertean species are found in marine habitats. Some, however, live in freshwater or on land. The name proboscis worm derives from the muscular eversible proboscis, which is housed in a fluid-filled chamber above the gut. This tube-shaped organ, which in many aquatic forms has a needlelike stylet, is typically used to trap prey. The stylet may also be used for burrowing; in land-dwelling species it may be used for rapid movement.

The ribbon worms are the simplest animals to possess a circulatory system and a gut with a separate mouth and anus. The body is usually long and slender and is often extended greatly during movement. Most species are less than 20 cm (8 inches) long, but the giant species Lineus longissimus may reach a length of 30 m (100 feet). Some forms that swim in deep water are flat and broad, with finlike appendages. Often uniformly coloured, various species of ribbon worms are vividly patterned with stripes, bands, speckles, or geometric shapes.

Male and female ribbon worms occur in most species, with annual reproduction typical. Usually eggs and sperm are released separately, and fertilization takes place externally. The fertilized egg develops by a process similar to that of flatworms (phylum Platyhelminthes), annelids (phylum Annelida), and mollusks (phylum Mollusca). Ribbon worms can develop in one of two ways: the most common is the direct method, without a larval stage; the other includes a ciliated larval stage, which may be one of two types. One kind, a free-swimming larva of complicated pattern known as the pilidium, is more common; the other type, similar to an adult, is called Desor’s larva. Larvae metamorphose into young ribbon worms after swimming for days or weeks in the plankton. Within the genera Prostoma and Geonemertes, the species may be either dioecious (i.e., separate male and female animals) or hermaphroditic (i.e. male and female reproductive organs in one animal). All ribbon worms have the ability to regenerate lost or damaged parts of their bodies; some species actually break up and form a number of fragments, which then grow into complete individuals. This mechanism provides asexual reproduction.

Sea otter (Enhydra lutris), also called great sea otter, rare, completely marine otter of the northern Pacific, usually found in kelp beds. Floats on back. Looks like sea otter laughing. saltwater otters

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Animal Group Names

The affinities of the nemerteans may lie with the flatworms, although molecular evidence generally fails to support this view; both groups have similar types of embryonic development and the same basic body plan. Unlike the flatworms, however, the ribbon worms have a complete gut and a circulatory system. 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.

Certain bloodworm (q.v.) species of the phylum Annelida are also sometimes known as proboscis worms.

This article was most recently revised and updated by John P. Rafferty.

ribbon worm

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