# Caecosagitta

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Species of worm

Caecosagitta Scientific classification Kingdom: Animalia Phylum: Chaetognatha Class: Sagittoidea Order: Aphragmophora Family: Sagittidae Genus: Caecosagitta Tokioka, 1965[2] Species: C. macrocephala Binomial name Caecosagitta macrocephala (Fowler, 1904)[1]

***Caecosagitta macrocephala*** is a deep sea marine [chaetognath](/source/Chaetognatha) that is distributed in meso- and bathypelagic layers. It has a very wide distribution that ranges from the Subantarctic to Subarctic Ocean. [3] Cecosagitta macrocephalas have large heads, hence their name “macro-cephala”. Within their eyes are photoreceptive regions that allow them to catch weak light at bathypelagic depths.[3] Along with their eyes, their gut or intestine has orange pigmentation and a luminous organ that gleams due to bioluminescence unlike some other species of Sagittidae.[4] To be more precise, the luminescent organ is located on the ventral edge of each anterior lateral fin.[4] It is the only member of the genus ***Caecosagitta***, and only one of the two known species of bioluminescent chaetognath, the other being the distantly related *[Eukrohnia fowleri](/source/Eukrohnia_fowleri)*.[2] *C. macrocephala* has a secreted bioluminescence that is thought to be [coelenterazine](/source/Coelenterazine) based.[2] The luciferase is highly unstable, being unable to survive a single freeze-thaw, and is rapidly inactivated at ice-cold temperatures.

*Caecosagitta macrocephala'*s bioluminescent organs consist of hexagonal chambers containing elongate ovoid particles—the organelles holding bioluminescent materials. No other luminous organism is known to use hexagonal packing to hold bioluminescent materials. [4]

*Caecosagitta macrocephala* found in the north-western Pacific and centre-east to south Atlantic Oceans, were found to consists of at least two cryptic species due to "speciation of the bathypelagic species from a mesopelagic precursor."[3]

## References

1. **[^](#cite_ref-Fowler_1-0)** Fowler, G. H. (1905). Biscayan plankton. Part III.—The Chætognatha. *Transactions of the Linnean Society of London*, (2)10, 55–87.

1. ^ [***a***](#cite_ref-Tokioka_2-0) [***b***](#cite_ref-Tokioka_2-1) [***c***](#cite_ref-Tokioka_2-2) Tokioka, T. (1965). The taxonomical outline of Chaetognatha. *Publications of the Seto Marine Biological Laboratory*, 12(5), 335–357.

1. ^ [***a***](#cite_ref-Miyamoto_et_al._3-0) [***b***](#cite_ref-Miyamoto_et_al._3-1) [***c***](#cite_ref-Miyamoto_et_al._3-2) Miyamoto, H., Machida, R. & Nishida, S. (2010). Genetic diversity and cryptic speciation of the deep-sea chaetognath *Caecosagitta macrocephala* (Fowler, 1904). *Deep-Sea Research Part II: Topical Studies in Oceanography*, 57(24–26), 2211--2219.

1. ^ [***a***](#cite_ref-Thuesen_et_al._4-0) [***b***](#cite_ref-Thuesen_et_al._4-1) [***c***](#cite_ref-Thuesen_et_al._4-2) Thuesen, E. V., Goetz, F. E. & Haddock, S. H. (2010). Bioluminescent organs of two deep-sea arrow-worms, *Eukrohnia fowleri* and *Caecosagitta macrocephala*, with further observations on bioluminescence in chaetognaths. *Biological Bulletin*, 219(2), 100–111.

Taxon identifiers Caecosagitta Wikidata: Q19359054 Wikispecies: Caecosagitta CoL: 84M22 EoL: 64867 GBIF: 2306914 IRMNG: 1199910 ITIS: 158754 NBN: NHMSYS0020787334 NCBI: 648570 Open Tree of Life: 249384 WoRMS: 105404 Caecosagitta macrocephala Wikidata: Q2678160 CoL: 69566 EoL: 512009 EUNIS: 25431 GBIF: 2306915 IRMNG: 10982826 ITIS: 158755 NBN: NHMSYS0020752066 NCBI: 648572 OBIS: 105431 Open Tree of Life: 249388 SeaLifeBase: 60607 WoRMS: 105431

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