Motyxia
Encyclopedia
Motyxia, or the Sierra luminous millipedes, is a genus of cyanide-producing millipedes in the order Polydesmida
endemic to the southern Sierra Nevada, Tehachapi
, and Santa Monica
mountain ranges of California. Members of this genus are blind and produce cyanide (like most species in the order Polydesmida). One of the most remarkable features of these millipedes is their ability to glow at a peak wavelength of 495 nm. This is the only known instance of bioluminescence
in the entire millipede class Diplopoda, occurring only in eight species of the genus Motyxia.
, Kern
, and Tulare
). All 8 species of Motyxia are bioluminescent. Motyxia sequoiae is the brightest and Motyxia pior the darkest. Light is emitted from the exoskeleton of the millipede continuously (the light intensifies when the millipede is handled). Emission of light is uniform across the exoskeleton, and all the appendages (legs, antennae) and body rings emit light. The internal organs and viscera do not emit light. Luminescence is generated by a biochemical process in the millipede's exoskeleton. The light originates by way of a photoprotein, which differs from the photogenic molecule luciferase
in firefly beetles.
Another creature that produces light from a photoprotein is the jellyfish Aequorea victoria
, which is notable for green fluorescent protein
(GFP) and widely used as a biomarker in molecular biology.
Motyxias photoprotein contains a porphyrin
and is about 104 kDa
in size. However, the structure of the luminescent photoprotein remains uncertain, and its homology
to molecules of closely related arthropods is unknown.
Scientists familiar with Motyxia were at odds over the function of bioluminescence in Motyxia. Various functions were suggested: a nighttime aposematic warning signal, that it had no function at all, or that it inadvertently attracted predators. A field study tested the hypothesis that bioluminescence acts as a warning signal. Based on the results of the field experiment conducted in California, in a spot where Motyxia are native, researchers found that bioluminescence strongly deterred nocturnal mammalian predators.
and giant sequoia forests, and notably also in meadows. The presence of xystodesmid millipedes in meadows is atypical for the family. Most species are observed under canopies of broad-leaf deciduous forests. All Motyxia species are exclusively nocturnal. During the day, individuals are burrowed beneath the soil. At night, they emerge (by an unknown mechanism not related to light since they're blind) and feed on decaying vegetation. Individuals of the species M. sequoiae have been observed climbing on tree trunks, possibly consuming algae and lichens adhering to the bark.
near Crystal Cave
. The southernmost population is of the species Motyxia monica in the Santa Monica Mountains near Los Angeles. The holotype
of M. monica, collected in 1944, was recorded from Sherman Oaks in Los Angeles County, California. A dubious historical record indicates a Riverside County
locality; however, recent collections in the area have not confirmed this.
Polydesmida
Polydesmida is the largest order of millipedes, with more than 2,700 species in more than 170 genera, including all the millipedes reported to produce hydrogen cyanide .-Description:...
endemic to the southern Sierra Nevada, Tehachapi
Tehachapi Mountains
The Tehachapi Mountains , regionally also called The Tehachapis, are a mountain range in the Transverse Ranges system of California in the Western United States...
, and Santa Monica
Santa Monica Mountains
The Santa Monica Mountains are a Transverse Range in Southern California, along the coast of the Pacific Ocean in the United States.-Geography:...
mountain ranges of California. Members of this genus are blind and produce cyanide (like most species in the order Polydesmida). One of the most remarkable features of these millipedes is their ability to glow at a peak wavelength of 495 nm. This is the only known instance of bioluminescence
Bioluminescence
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...
in the entire millipede class Diplopoda, occurring only in eight species of the genus Motyxia.
Bioluminescence
Motyxia, which are the only known bioluminescent species in the millipede class Diplopoda (about 12,000 known species), are restricted to three counties in California (Los AngelesLos Angeles County, California
Los Angeles County is a county in the U.S. state of California. As of 2010 U.S. Census, the county had a population of 9,818,605, making it the most populous county in the United States. Los Angeles County alone is more populous than 42 individual U.S. states...
, Kern
Kern County, California
Spreading across the southern end of the California Central Valley, Kern County is the fifth-largest county by population in California. Its economy is heavily linked to agriculture and to petroleum extraction, and there is a strong aviation and space presence. Politically, it has generally...
, and Tulare
Tulare County, California
Tulare County is a county located in the Central Valley of the U.S. state of California, south of Fresno. Sequoia National Park is located in the county, as are part of Kings Canyon National Park, in its northeast corner , and part of Mount Whitney, on its eastern border...
). All 8 species of Motyxia are bioluminescent. Motyxia sequoiae is the brightest and Motyxia pior the darkest. Light is emitted from the exoskeleton of the millipede continuously (the light intensifies when the millipede is handled). Emission of light is uniform across the exoskeleton, and all the appendages (legs, antennae) and body rings emit light. The internal organs and viscera do not emit light. Luminescence is generated by a biochemical process in the millipede's exoskeleton. The light originates by way of a photoprotein, which differs from the photogenic molecule 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...
in firefly beetles.
Another creature that produces light from a photoprotein is the jellyfish Aequorea victoria
Aequorea victoria
Aequorea victoria, also sometimes called the crystal jelly, is a bioluminescent hydrozoan jellyfish, or hydromedusa, that is found off the west coast of North America. This species is thought to be synonymous with Aequorea aequorea of Osamu Shimomura, the discoverer of green fluorescent protein . ...
, which is notable for green fluorescent protein
Green fluorescent protein
The green fluorescent protein is a protein composed of 238 amino acid residues that exhibits bright green fluorescence when exposed to blue light. Although many other marine organisms have similar green fluorescent proteins, GFP traditionally refers to the protein first isolated from the...
(GFP) and widely used as a biomarker in molecular biology.
Motyxias photoprotein contains a porphyrin
Porphyrin
Porphyrins are a group of organic compounds, many naturally occurring. One of the best-known porphyrins is heme, the pigment in red blood cells; heme is a cofactor of the protein hemoglobin. Porphyrins are heterocyclic macrocycles composed of four modified pyrrole subunits interconnected at...
and is about 104 kDa
KDA
KDA may refer to:* Karachi Development Authority* Kongsberg Defence & Aerospace* Kotelawala Defence Academy* Kramer Design Associates* Lithium diisopropylamide, KDA is the potassium analogue of lithium diisopropylamideOr kDa may refer to:...
in size. However, the structure of the luminescent photoprotein remains uncertain, and its homology
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
to molecules of closely related arthropods is unknown.
Scientists familiar with Motyxia were at odds over the function of bioluminescence in Motyxia. Various functions were suggested: a nighttime aposematic warning signal, that it had no function at all, or that it inadvertently attracted predators. A field study tested the hypothesis that bioluminescence acts as a warning signal. Based on the results of the field experiment conducted in California, in a spot where Motyxia are native, researchers found that bioluminescence strongly deterred nocturnal mammalian predators.
Characteristics
- Medium (3 cm in length), "flat-backed" polydesmidaPolydesmidaPolydesmida is the largest order of millipedes, with more than 2,700 species in more than 170 genera, including all the millipedes reported to produce hydrogen cyanide .-Description:...
n millipedes. Typically orange-pink in color (except M. pior). - Bioluminescent (variable brightness, from the lowest intensity of M. pior to the highest in M. sequoiae). Bioluminescence intensifies when handled.
- Fluorescent (millipedes in the tribe Xystocheirini display some of the brightest fluorescence of the U.S. Xystodesmidae species)
- Anterior 2-3 diplosegments oriented cephalically (most distinct in M. sequoiae, nearly indistinct in Motyxia porrecta)
- Dorsal bumps (papillae) on metatergites absent
- Geographically restricted to Los Angeles, Kern and Tulare counties in California
Habitat
Motyxia species occur in live oakLive oak
Live oak , also known as the southern live oak, is a normally evergreen oak tree native to the southeastern United States...
and giant sequoia forests, and notably also in meadows. The presence of xystodesmid millipedes in meadows is atypical for the family. Most species are observed under canopies of broad-leaf deciduous forests. All Motyxia species are exclusively nocturnal. During the day, individuals are burrowed beneath the soil. At night, they emerge (by an unknown mechanism not related to light since they're blind) and feed on decaying vegetation. Individuals of the species M. sequoiae have been observed climbing on tree trunks, possibly consuming algae and lichens adhering to the bark.
Distribution
Motyxia species are geographically restricted to 3 counties in California: Los Angeles, Kern and Tulare. Species predominately occur in the Santa Monica, Tehachapi, and southern Sierra Nevada Mountains. The northernmost population of the genus is of the species M. pior in Sequoia National ParkSequoia National Park
Sequoia National Park is a national park in the southern Sierra Nevada east of Visalia, California, in the United States. It was established on September 25, 1890. The park spans . Encompassing a vertical relief of nearly , the park contains among its natural resources the highest point in the...
near Crystal Cave
Crystal Cave (Sequoia National Park)
Crystal Cave is a marble cave in Sequoia National Park, in the U.S. state of California. It is one of at least 240 known caves in the park.It is in the Giant Forest region, between the Ash Mountain entrance of the park and Giant Forest....
. The southernmost population is of the species Motyxia monica in the Santa Monica Mountains near Los Angeles. The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
of M. monica, collected in 1944, was recorded from Sherman Oaks in Los Angeles County, California. A dubious historical record indicates a Riverside County
Riverside County, California
Riverside County is a county in the U.S. state of California. One of 58 California counties, it covers in the southern part of the state, and stretches from Orange County to the Colorado River, which forms the state border with Arizona. The county derives its name from the city of Riverside,...
locality; however, recent collections in the area have not confirmed this.
External links
- Osamu Shimomura mbl.edu/news/features/shimomura.html
- J. Woodland Hastings mcb.harvard.edu/hastings/dino.html
- Minoru Isobe iar.nagoya-u.ac.jp/2004PBF/Eng_Isobe.html
- Evolution of bioluminescence in millipedes apheloria.org