Chaetognatha
Chaetognatha,[1] commonly known as arrow worms, are a phylum of small predatory marine animals. They are present in huge numbers in plankton worldwide.
| Arrow worms Temporal range: Lower Cambrian to Recent
| |
|---|---|
| |
| Spadella cephaloptera | |
| Scientific classification | |
| Kingdom: | |
| Superphylum: | Protostomia (disputed)
|
| Phylum: | Chaetognatha Leuckart 1854
|
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.[2] Some species are known to use the neurotoxin tetrodotoxin to subdue their prey.[3]
Chaetognaths appear to have originated in the Cambrian Period. Complete body fossils have been described from China,[4][5] and the Middle Cambrian Burgess Shale of British Columbia.[6]
These animals are usually considered a type of protostome.
Chaetognatha Media
Drawing of ten different chaetognath species, showing morphological similarity and diversity.
The jaw organ of a chaetognath of the genus Sagitta
Anatomy of a chaetognath (Spadella cephaloptera)
Comparison of size between various viruses and the bacteria E. coli
References
- ↑ meaning hair-jaws
- ↑ Bone Q.; et al. (1991). The biology of chaetognaths. London: Oxford University Press.
- ↑ Thuesen, E.V.; et al. (1991), "The tetrodotoxin venom of chaetognaths", in Bone, Q. (ed.), The biology of chaetognaths, London: Oxford University Press, pp. 55–60
- ↑ Chen J.-Y., and D.-Y. Huang. 2002. A possible Lower Cambrian chaetognath (arrow worm). Science 298:187.
- ↑ Hu S.-X. 2005. Taphonomy and palaeoecology of the Early Cambrian Chengjiang Biota from Eastern Yunnan, China. Berliner Paläobiologische Abhandlungen 7:1–197.
- ↑ Szaniawski H. 2005. Cambrian chaetognaths recognized in Burgess Shale fossils. Acta Palaeontologica Polonica 50:1-8.