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Arrow worm facts for kids

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Arrow worms
Temporal range: Lower Cambrian to Recent
Spadella cephaloptera
Scientific classification
Protostomia (disputed)

Leuckart 1854

Chaetognatha, commonly known as arrow worms, are a phylum of small predatory marine animals. They are present in huge numbers in plankton worldwide.

About 20% of the known species are benthic and can attach to algae or rocks. They are found in all marine waters from surface tropical waters and shallow tide pools to the deep sea and polar regions. Most chaetognaths are transparent and are torpedo shaped, but some deep-sea species are orange. They range in size from 2 to 120 millimetres (0.079 to 4.724 in).

Despite the huge numbers, there are only about 120 modern species in 20 genera. Some species are known to use the neurotoxin tetrodotoxin to subdue their prey.

Chaetognaths appear to have originated in the Cambrian Period. Complete body fossils have been described from China, and the Middle Cambrian Burgess Shale of British Columbia.

These animals are usually considered a type of protostome.

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See also

Kids robot.svg In Spanish: Chaetognatha para niños

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