Vargula hilgendorfii
Encyclopedia
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
. V. hilgendorfii was formerly more common, but its numbers have recently fallen significantly.
. 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.
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. 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.
(1839–1904). The bioluminescence of V. hilgendorfii was a research topic for a long time; the first research dates back to the year 1917.
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. 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
.
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
as umi-hotaru, is a species of ostracod
Ostracod
Ostracoda is a class of the Crustacea, sometimes known as the seed shrimp because of their appearance. Some 65,000 species have been identified, grouped into several orders....
crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
. It is the only member of genus Vargula to inhabit Japanese waters; all other members of its genus inhabit the Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
, the Caribbean Sea
Caribbean Sea
The Caribbean Sea is a sea of the Atlantic Ocean located in the tropics of the Western hemisphere. It is bounded by Mexico and Central America to the west and southwest, to the north by the Greater Antilles, and to the east by the Lesser Antilles....
, and waters off the coast of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
. V. hilgendorfii was formerly more common, but its numbers have recently fallen significantly.
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.Bioluminescence
V. hilgendorfii is known for its bioluminescenceBioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
. It produces a blue-coloured light by a specialized chemical reaction of the substrate luciferin
Luciferin
Luciferins are a class of light-emitting biological pigments found in organisms that cause bioluminescence...
and the enzyme luciferase
Luciferase
Luciferase is a generic term for the class of oxidative enzymes used in bioluminescence and is distinct from a photoprotein. One famous example is the firefly luciferase from the firefly Photinus pyralis. "Firefly luciferase" as a laboratory reagent usually refers to P...
.The luciferase enzyme consists of a 555 amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
long peptide with a molecular mass of 61627 u
Atomic mass unit
The unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...
, while the luciferine vargulin
Vargulin
Vargulin, or cypridina luciferin, is the luciferin found in the ostracod Cypridina hilgendorfii also named Vargula hilgendorfii....
has only a mass of 405.5 u. A suggested biosynthesis for vargulin divides the molecule into a tryptophan
Tryptophan
Tryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...
, a arginin and a isoleucine
Isoleucine
Isoleucine is an α-amino acid with the chemical formula HO2CCHCHCH2CH3. It is an essential amino acid, which means that humans cannot synthesize it, so it must be ingested. Its codons are AUU, AUC and AUA....
subunit.
The maximum in the wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
of the luminescence is dependent on pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
and salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
of the water in which the reaction takes place. It varies between 448 and 463 nm
Nanometre
A nanometre is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre .The nanometre is often used to express dimensions on the atomic scale: the diameter...
, with the maximum being at 452 nm in sea water. The substrate oxidizes when ejected from the upper-lip gland, with luciferase as a catalyst. The reaction produces carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
, 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.
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.History
The species was first described by Gustav Wilhelm Müller in 1890. He named the species after the zoologist Franz Martin HilgendorfFranz Martin Hilgendorf
Franz Martin Hilgendorf was a German zoologist and paleontologist. Hilgendorf's research on fossil snails from the Steinheim crater in the early 1860s became a palaeontological evidence for the theory of evolution published by Charles Darwin in 1859.-Life and work:Franz Hilgendorf was born...
(1839–1904). The bioluminescence of V. hilgendorfii was a research topic for a long time; the first research dates back to the year 1917.
Dried sea-firefly were sometimes used as a light source by the Japanese army during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
to read maps in the dim light. 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
Vargulin
Vargulin, or cypridina luciferin, is the luciferin found in the ostracod Cypridina hilgendorfii also named Vargula hilgendorfii....
.