Polyxenida

Source: Wikipedia, the free encyclopedia.
Not to be confused with Polyxenidas.
"Bristle millipede" redirects here. Not to be confused with the bristly millipede, Polyxenus lagurus.

Polyxenida
Temporal range: Barremian–Present
Polyxenus lagurus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Myriapoda
Class: Diplopoda
Subclass: Penicillata
Latrielle, 1831
Order: Polyxenida
Verhoeff, 1934
Families
Synonyms

Subclass
Pselaphognatha

Latzel
, 1884
Schizocephala Verhoeff, 1926
Order
Ancyrotricha
Cook
, 1895

Condexenus biramipalpus and Phryssonotus brevicapensis
Other Phryssonotus

Polyxenida is an

millipedes
readily distinguished by a unique body plan consisting of a soft, non-calcified body ornamented with tufts of bristles – traits that have inspired the common names "bristly millipedes" or "pincushion millipedes". There are at least 86 species in four families worldwide, and are the only living members of the subclass Penicillata.

Description

Polyxenida differ from other millipedes in having a soft, non-calcified

setae, fewer legs (no more than 17 pairs), and an absence of copulatory appendages in males. Individuals are small, not exceeding 7 millimeters (0.28 inches). Adults in most species have 13 pairs of legs, but in one species (Lophoturus madecassus), they have only 11 pairs of legs, and in one genus (Phryssonotus), they have 17 pairs of legs, except for one species (Phryssonotus brevicapensis) in which they (along with those in one other species, Condexenus biramipalpus) have 15 pairs of legs.[1] Millipedes in this order develop by hemianamorphosis.[2]

Defense

Bristly millipedes lack the chemical defenses and hard exoskeleton of other millipedes,[3] and instead employ a unique defense mechanism: the distinctive barbed bristles can easily detach and become entangled in the limbs and mouth-parts of predatory insects, effectively immobilizing them.[4]

Reproduction

Male Polyxenidans lack the modified sperm-transferring appendages (gonopods) found in most other millipede groups. As a result, sperm transfer is indirect: males deposit a spermatophore that is subsequently picked up by females.[5]

Many species reproduce asexually by way of parthenogenesis, wherein females lay eggs without mating and males are absent or rare.[6]

Classification

Phryssonotus brevicapensis (Synxenidae), a species from South Africa described in 2011[7]

Polyxenida is the only

Helminthomorpha.[8][9]

In 2003 the Polyxenida contained 159 valid species and/or subspecies,[10] although at least eight new species have been described since 2010.[7][11][12]

Fossil history

The earliest representatives of Polyxenida are found in Lebanese amber from the Early Cretaceous period.[13]
Some authors place the extinct orders

Eoarthropleurida (each represented by a single genus) within the Penicillata as a sister group to Polyxenida.[14][15]

References

  1. doi:10.1163/9789004188273_017
    .
  2. doi:10.1111/j.1096-3642.1993.tb00305.x
    .
  3. ^ Shelley, Rowland M. "The Myriapoda (Millipedes, Centipedes) Featuring the North American Fauna". Retrieved 12 October 2013.
  4. PMID 8855269
    .
  5. ^ Shelley, Rowland M. (1999). "Centipedes and Millipedes with Emphasis on North American Fauna". The Kansas School Naturalist. 45 (3): 1–16. Archived from the original on 2016-11-12. Retrieved 2013-10-12.
  6. ^ Barnes, Robert D. (1987). "15. The myriapods". Invertebrate zoology (5th ed.). Philadelphia: Saunders College Pub. pp. 674–683.
  7. ^
    PMID 22303097
    .
  8. PMID 17163800
    .
  9. doi:10.11646/zootaxa.3148.1.32
    .
  10. ^ Nguyen Duy-Jacquemin, M.; J.-J. Geoffroy (2003). "A revised comprehensive checklist, relational database, and taxonomic system of reference for the bristly millipedes of the world (Diplopoda, Polyxenida)". African Invertebrates. 44 (1): 89–101.
  11. PMID 22303098
    .
  12. PMID 23794829
    .
  13. ^ Duy-Jacquemin, MN; Azar, D (2004). "The oldest records of Polyxenida (Myriapoda, Diplopoda): New discoveries from the Cretaceous ambers of Lebanon and France". Geodiversitas. 26 (4): 631–641.
  14. PMID 19944188
    .
  15. ^ Kraus, O; C. Brauckman (2003). "Fossil giants and surviving dwarfs. Arthropleurida and Pselaphognatha (Ateolocerata, Diplopoda): characters, phylogenetic relationships and construction". Verh. Naturwiss. Ver. Hamburg. 40 (5): 5–50.

External links