Sierra luminous millipede
| Motyxia | |
|---|---|
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| A replica Motyxia at the American Museum of Natural History | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Myriapoda |
| Class: | Diplopoda |
| Order: | Polydesmida |
| Family: | Xystodesmidae |
| Genus: |
Motyxia Chamberlin, 1941 |
| Type species | |
|
Motyxia kerna Chamberlin, 1941 |
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| Species | |
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M. bistipita |
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| Synonyms | |
|
Amplocheir Chamberlin, 1949 |
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M. bistipita
M. kerna
M. monica
M. pior
M. porrecta
M. sequoia
M. sequoiae
M. tiemanni
M. tularea
Amplocheir Chamberlin, 1949
Luminodesmus Loomis & Davenport, 1951
Motyxia is a genus of cyanide-producing millipedes (collectively known as Sierra luminous millipedes or motyxias) that are endemic to the southern Sierra Nevada, Tehachapi, and Santa Monica mountain ranges of California. Motyxias are blind and produce the poison cyanide, like all members of the Polydesmida. All species have the ability to glow brightly: some of the few known instances of bioluminescence in millipedes.
Adult Motyxia reach 3 to 4 cm in length, 4.5 to 8 mm wide, with 20 body segments, excluding the head. Females are slightly larger than males. Like other polydesmidans ("flat-backed" millipedes) they lack eyes and have prominent paranota (lateral keels). They are typically tan to orange-pink in color (except M. pior), with a dark mid-dorsal line. M. pior is the most variable in color, and ranges from dark gray to greenish-yellow to bright orange. They lack bumps on the metatergites (the dorsal plates possessing paranota), giving a somewhat smooth appearance. The anterior 2-3 diplosegments are oriented cephalically (towards the head), a trait most distinct in M. sequoiae, nearly indistinct in Motyxia porrecta. They are fluorescent under black light (millipedes in the tribe Xystocheirini display some of the brightest fluorescence of the U.S. Xystodesmidae species). Most uniquely they are bioluminescent: emitting light of their own production.
The 9 species and 11 subspecies species of Motyxia are some of the few known bioluminescent species of millipedes, a class of about 12,000 known species.Motyxia sequoiae glows the brightest and Motyxia pior the dimmest. Light is emitted from the exoskeleton of the millipede continuously, with peak wavelength of 495 nm (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.
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