Myriapoda

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Myriapods
Temporal range: Wenlock–Present
Representatives of the four extant myriapod classes. Clockwise from top left:
Diplopoda, Symphyla, and Pauropoda
.
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Clade: Mandibulata
Subphylum: Myriapoda
Latreille, 1802
Classes[1]

Myriapods (from

Ancient Greek μυρίος (muríos) 'ten thousand', and πούς (poús) 'foot') are the members of subphylum Myriapoda, containing arthropods such as millipedes and centipedes. The group contains about 13,000 species, all of them terrestrial.[2]

The

phylogenetic classification
of myriapods is still debated.

The scientific study of myriapods is myriapodology, and those who study myriapods are myriapodologists.[8]

Anatomy

The head of Scutigera coleoptrata, showing antennae, compound eyes and mouthparts

Myriapods have a single pair of

tracheal system similar to that of insects. There is a long tubular heart that extends through much of the body, but usually few, if any, blood vessels.[11]

Malpighian tubules excrete nitrogenous waste into the digestive system, which typically consists of a simple tube. Although the ventral nerve cord has a ganglion in each segment, the brain is relatively poorly developed.[11]

During mating, male myriapods produce a packet of sperm, or spermatophore, which they must transfer to the female externally; this process is often complex and highly developed. The female lays eggs which hatch as much-shortened versions of the adults, with only a few segments and as few as three pairs of legs. With the exception of the two centipede orders Scolopendromorpha and Geophilomorpha, which have epimorphic development (all body segments are formed segments embryonically), the young add additional segments and limbs as they repeatedly moult to reach the adult form.[11]

The process of adding new segments during postembryonic growth is known as anamorphosis, of which there are three types: euanamorphosis, emianamorphosis, and teloanamorphosis. In euanamorphosis, every moult is followed by addition of new segments, even after reaching sexual maturity; in emianamorphosis, new segments are added until a certain stage, and further moults happen without addition of segments; and in teloanamorphosis, where the addition of new segments stops after the adult form is reached, after no further moults occur.[12]

Ecology

Part of a series on
Myriapods
Classes
Pauropods
Anatomy
Millipede gonopods
Notable species
Eopauropus balticus • Scolopendra gigantea • Scutigerella immaculata
Interactions with humans
Centipede bite


Myriapods are most abundant in moist forests, where they fulfill an important role in breaking down decaying plant material,

predators
.

A few species of centipedes and millipedes are able to produce light and are therefore

body segments fused into pairs, giving the appearance that each segment bears two pairs of legs
, while the other three groups have a single pair of legs on each body segment.

Although not generally considered dangerous to humans, many millipedes produce noxious

benzoquinones) which in rare cases can cause temporary blistering and discolouration of the skin.[17] Large centipedes, however, can bite humans, and although the bite may cause intense pain and discomfort, fatalities are extremely rare.[18]

Classification

Paradoxopoda hypothesis, Chelicerata is the closest. This last hypothesis, although supported by few, if any, morphological characters, is supported by a number of molecular studies.[20]

A 2020 study found numerous characters of the eye and preoral region suggesting that the closest relatives to crown myriapods are the extinct Euthycarcinoids.[21] There are four classes of extant myriapods, Chilopoda (centipedes), Diplopoda, Pauropoda and Symphyla, containing a total of around 12,000 species.[22] While each of these groups of myriapods is believed to be monophyletic, relationships among them are less certain.[23]

Centipedes

Main article: Centipede
Tachypodoiulus niger, a millipede
A species of Scutigerella, a genus of Symphylan.

Nannarrup hoffmani (less than 12 mm or 1⁄2 in in length)[24] to the giant Scolopendra gigantea
, which may exceed 30 centimetres (12 in).

Millipedes

Main article: Millipede

Eumillipes persephone, the first species known to have 1,000 or more legs, possessing 1,306 of them.[27] Pill millipedes are much shorter, and are capable of rolling up into a ball, like pillbugs
.

Symphyla

Main article: Symphyla

Symphylans, or garden centipedes, are closely related to centipedes and millipedes.[28][29] They are 3 to 6 cm long, and have 6 to 12 pairs of legs, depending on their life stage.[28][29][30] Their eggs, which are white and spherical and covered with small hexagonal ridges, are laid in batches of 4 to 25 at a time, and usually take up to 40 days to hatch.[28][29][30] There are about 200 species worldwide.[31]

Pauropoda

Main article: Pauropoda
A Eurypauropodid Pauropod.

tergites fused across pairs of segments, similar to the more complete fusion of segments seen in millipedes.[32]

Arthropleuridea

Main article: Arthropleuridea
Arthropleura armata, an arthropleuridean

Arthropleurideans were ancient myriapods that are now extinct, known from the late Silurian to the Permian. The most famous members are from the genus Arthropleura, which was a giant, probably herbivorous, animal that could be up to 2.63 metres (8 ft 8 in) long,[33] but the group also includes species less than 1 cm (0.39 in). Arthropleuridea was historically considered a distinct class of myriapods, but since 2000 scientific consensus has viewed the group as a subset of millipedes, although the relationship of arthropleurideans to other millipedes and to each other is debated.[34][35]

Myriapod relationships

Some of the various hypotheses of myriapod phylogeny. Morphological studies (trees a and b) support a sister grouping of Diplopoda and Pauropoda, while studies of DNA or amino acid similarities suggest a variety of different relationships, including the relationship of Pauropoda and Symphyla in tree c.

A variety of groupings (

DNA sequence and amino acid similarities).[36][37]

See also

  • Euthycarcinoidea, a group of enigmatic arthropods that may be ancestral to myriapods
  • Colonization of land
    , major evolutionary stages leading to terrestrial organisms
  • Metamerism, the condition of multiple linearly repeated body segments

References

  1. ^ "Myriapoda". Integrated Taxonomic Information System.
  2. ^ a b c Ben Waggoner (February 21, 1996). "Introduction to the Myriapoda". University of California, Berkeley. Retrieved November 9, 2021.
  3. ^
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  5. ^ Rowland Shelley & Paul Marek (March 1, 2005). "Millipede Fossils". East Carolina University. Archived from the original on May 27, 2011.
  6. doi:10.1007/s12052-011-0357-y
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  8. ISBN 978-0-618-05684-2
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  9. ^ Deep Metazoan Phylogeny: The Backbone of the Tree of Life. New insights from analyses of molecules, morphology, and theory of data analysis.
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  12. doi:10.1111/j.1096-3642.1993.tb00305.x
    .
  13. Britannica Concise Encyclopedia
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  14. ^ Barber, A.D. (2009). "Littoral myriapods: a review" (PDF). Soil Organisms. 81 (3): 735–760. Archived from the original (PDF) on 2016-03-03. Retrieved 2013-11-05.
  15. ^ Barber, A.D., ed. (2013). "World Database of Littoral Myriapoda". World Register of Marine Species. Retrieved 25 October 2013.
  16. ^ Rosenberg, Joerg; Meyer-Rochow, Victor Benno (2009). Meyer-Rochow V.B. (ed.). Bioluminescence in Focus - a collection of illuminating essays. Research Signpost; Trivandrum, Kerala, India. pp. 139–147.
  17. ^ "Strange and Unusual Millipedes". herper.com. Archived from the original on April 2, 2012. Retrieved July 2, 2007.
  18. PMID 11434497
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  19. doi:10.1163/18759866-07303002
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    ISBN 978-0-642-56850-2. Archived from the original
    (PDF) on 25 October 2007. Retrieved 1 January 2011.
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  24. ^ "City Centipede: An Urban Legend with Real Legs - TIME". 2008-04-30. Archived from the original on 2008-04-30. Retrieved 2022-10-30.
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  27. S2CID 245317751
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  28. ^ a b c Gesell, Stanley; Calvin, Dennis (2017-03-09). "Garden Symphylan as a Pest of Field Crops".
  29. ^ a b c University, Utah State. "Sympylans (Garden Centipede)". extension.usu.edu. Retrieved 2022-10-30.
  30. ^ a b "Symphylan Identification". 2007-08-03. Archived from the original on 2007-08-03. Retrieved 2022-10-30.
  31. ^ "Numbers of Living Species in Australia and the World" (PDF). 2009-09-26. Archived from the original (PDF) on 2009-09-26. Retrieved 2022-10-30.
  32. ^ David Kendall (June 6, 2005). "Pauropods & Symphylids". Kendall Bioresearch.
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  34. S2CID 129597005
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  36. ^ Edgecombe GD; Giribet G (2002). "Myriapod phylogeny and the relationships of Chilopoda" (PDF). In J Llorente Bousquets; JJ Morrone; HP Ulloa (eds.). Biodiversidad, Taxonomia y Biogeografia de Artropodos de Mexico: Hacia una S´ıntesis de su Conocimiento. Univ. Nac. Aut´on Mexico: Prensas Ciencias. pp. 143–168.
  37. ^
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  38. PMID 23185239
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External links

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