Chaetognatha (Arrow Worms)


Chaetognaths are elongate bilaterally symmetrical marine animals, ranging from 0.2 to 12 cm long. They have a distinct head bearing grasping spines, and a tail fin together with one or two paired fins. The bipartite body and head contain powerful rapidly contracting muscles, but apart from gut and gonads, internal organs are absent; there is no heart or blood system.

Keywords: chaetognath; arrow worm; predator; taxonomic isolation

Figure 1.

Scanning electron micrograph of head showing grasping hooks, mouth and teeth. The base of the grasping hooks is partially covered by the retractable prepuce.

Figure 2.

External appearance of Sagitta.

Figure 3.

Transverse section of a typical chaetognath showing internal anatomy.


Further Reading

Bone Q, Kapp H and Pierrot‐Bults AC (eds) (1991) The Biology of Chaetognaths. Oxford: Oxford University Press.

Shinn GL and Roberts ME (1994) Ultrastructure of hatching chaetognaths (Ferosagitta hispida): phylogenetic implications. Journal of Morphology 219: 143–163.

Telford MJ and Holland PWH (1993) The phylogenetic affinities of the Chaetognaths: a molecular analysis. Molecular Biology and Evolution 10: 660–676.

Telford MJ and Holland PWH (1997) Evolution of 28S ribosomal DNA in Chaetognaths: duplicate genes and molecular phylogeny. Journal of Molecular Evolution 44: 135–144.

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How to Cite close
Bone, Quentin(Apr 2001) Chaetognatha (Arrow Worms). In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0001616]