Nemertea

Nemertea is a phylum of mostly marine invertebrates called ribbon worms. Its members capture prey with a muscular proboscis that can be everted from a fluid-filled cavity.

Proboscis: A tubular or elongated organ that can extend from an animal’s body, often for feeding or sensing. Nemerteans use an eversible proboscis to seize or entangle prey.
Bilateria: The animal group whose members develop bilateral symmetry and three germ layers. Nemerteans belong to this broad lineage of bilaterally organized animals.
Platyhelminthes: A phylum of flatworms that includes free-living and parasitic species. Flatworms lack nemerteans’ separate proboscis cavity and usually lack an anus.
Cerebratulus lacteus: A North Atlantic ribbon worm known for its long, flattened body and mucus production. This species illustrates the size and defensive secretions found among nemerteans.
Hoplonemertea: A nemertean group whose proboscis typically bears a stylet. Its characteristic armature helps define one major branch of ribbon worms.
Rhynchocoel: A fluid-filled cavity that houses the proboscis in nemertean worms. Its pressure helps drive the proboscis outward during prey capture.
Acoelomate: An animal lacking a fluid-filled body cavity between the gut and body wall. Nemerteans lack a true coelom, though they possess a rhynchocoel.
Annelida: A phylum of segmented worms, including earthworms, leeches, and bristle worms. Annelids are segmented; nemerteans generally have unsegmented bodies.
Lineus longissimus: A marine ribbon worm capable of growing to exceptional lengths when extended. Its extreme length demonstrates the body form’s capacity for elongation.
Palaeonemertea: A traditionally recognized group of nemerteans with comparatively simple anatomical features. It represents an early-diverging lineage in many classifications.

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LophotrochozoaBroader topic: Ribbon worms represent another distinct animal lineage placed within Lophotrochozoa.