Vargula hilgendorfii

Vargula hilgendorfii
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Crustacea
Class:	Ostracoda
Order:	Myodocopida
Family:	Cypridinidae
Genus:	Vargula
Species:	V. hilgendorfii
Binomial name
Vargula hilgendorfii (G. W. Müller, 1890)
Synonyms
Cypridina hilgendorfii

Vargula hilgendorfii, sometimes called the sea-firefly, one of three bioluminescent species known in Japan as umi-hotaru, is a species of ostracod crustacean. It is the only member of genus Vargula to inhabit Japanese waters; all other members of its genus inhabit the Gulf of Mexico, the Caribbean Sea, and waters off the coast of California.^[1] V. hilgendorfii was formerly more common, but its numbers have recently fallen significantly.^[2]

Description

V. hilgendorfii is a small animal, only 3 millimetres long. It is nocturnal and lives in the sand at the bottom of shallow water. At night, it feeds actively.^[2][3]

Bioluminescence

V. hilgendorfii glowing

The luciferin from Vargula hilgendorfii

V. hilgendorfii is known for its bioluminescence. It produces a blue-coloured light by a specialized chemical reaction of the substrate luciferin and the enzyme luciferase.The luciferase enzyme consists of a 555 amino acid long peptide with a molecular mass of 61627 u, while the luciferine vargulin has only a mass of 405.5 u. A suggested biosynthesis for vargulin divides the molecule into a tryptophan, a arginin and a isoleucine subunit.^[1][2]

The maximum in the wavelength of the luminescence is dependent on pH and salinity of the water in which the reaction takes place. It varies between 448 and 463 nm, with the maximum being at 452 nm in sea water.^[4] The substrate oxidizes when ejected from the upper-lip gland, with luciferase as a catalyst. The reaction produces carbon dioxide, oxyluciferin, and blue light. As a intermediate a 1,2-dioxetane ring is formed, this intermediate is also formed in reaction of other bioluminescent lifeforms and also in the chemoluminescence of glow sticks.^[5]

Distribution

V. hilgendorfii is indigenous to the water off of the southern Japanese coast. DNA and RNA analysis indicated that V. hilgendorfii migrated slowly northward after the last ice age. The poor swimming abilities and the fact the eggs are hatched in the uterus and live young are born limit the ability to migrate.^[3]

History

The species was first described by Gustav Wilhelm Müller in 1890. He named the species after the zoologist Franz Martin Hilgendorf (1839–1904). The bioluminescence of V. hilgendorfii was a research topic for a long time; the first research dates back to the year 1917.^[6]

Dried sea-firefly were sometimes used as a light source by the Japanese army during World War II to read maps in the dim light.^[7] In 1962, the name of the species was changed from Cypridina hilgendorfii to Vargula hilgendorfii. It took until 1968 when Japanese scientists were able to determine the structure of the luciferine vargulin.^[8]

References

1. ^ ^{a b} Nakajima, Yoshihiro; et al. (2004). "cDNA Cloning and Characterization of a Secreted Luciferase from the Luminous Japanese Ostracod, Cypridina noctiluca". Japan Science and Technology Information Aggregator, Electronic. http://www.jstage.jst.go.jp/article/bbb/68/3/565/_pdf. 
2. ^ ^{a b c} Thompson, Eric M.; Shigekazu Nagata and Frederick I. Tsuji (1989). "Cloning and expression of cDNA for the luciferase from the marine ostracod Vargula hilgendorfii". Proceedings of the National Academy of Sciences 86 (17): 6567–6571. doi:10.1073/pnas.86.17.6567. JSTOR 34574. PMC 297885. PMID 2771943. http://www.pnas.org/content/86/17/6567.full.pdf+html. Retrieved 8 February 2010. 
3. ^ ^{a b} Ogoh, Katsunori; Ohmiya, Yoshihiro (2005). "Biogeography of luminous marine ostracod driven irreversibly by the Japan Current". Molecular Biology and Evolution 22 (7): 1543–1545. doi:10.1093/molbev/msi155. PMID 15858206. 
4. ^ Shimomura, Osamu (2006). "The ostracod Cypridina (Vargula) and other luminous crustaceans". Bioluminescence: chemical principles and methods. World Scientific. pp. 47–89. ISBN 9789812568014. http://books.google.com/books?id=DNrTfH5PcWoC&pg=PA64. 
5. ^ McCapra, Frank (1976). "Chemical mechanisms in bioluminescence". Accounts of Chemical Research 9 (6): 201–208. doi:10.1021/ar50102a001. 
6. ^ Harvey, E. N. (1916). "Studies on bioluminescence". American Journal of Physiology 42 (2): 318–341. http://ajplegacy.physiology.org/cgi/reprint/42/2/318.pdf. 
7. ^ Wiedenmann, Jörg (2008). "Marine proteins". In Patrick J. Walsh. Oceans and human health: risks and remedies from the seas. Academic Press. pp. 469–495. ISBN 9780123725844. http://books.google.com/books?id=hfrt4KRdNT8C&pg=PA477. 
8. ^ Morin, James G. (2010). "Based on a review of the data, use of the term cypridinid solves the Cypridina/Vargula dilemma for naming the constituents of the luminescent system of ostracods in the family Cypridinidae". Luminescence 26: in press. doi:10.1002/bio.1178.