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Millipede

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Title: Millipede  
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Subject: Insect, Chordeumatida, Sphaerotheriida, Stemmiulidae, Callipodida
Collection: Detritivores, Millipedes, Silurian First Appearances
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Millipede

Millipedes
Temporal range: 428–0Ma
Є
O
S
D
C
P
T
J
K
Pg
N
Late Silurian to Recent
An assortment of millipedes
(not to scale)
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Myriapoda
Class: Diplopoda
De Blainville in Gervais, 1844 
Subclasses
Diversity
16 orders, c. 12,000 species

Millipedes (class (biology) Diplopoda) are myriapodous arthropods that have two pairs of legs on most body segments. Each double-legged segment is a result of two single segments fused together as one—the name "Diplopoda" comes from the Greek words διπλοῦς (diplous), "double" and ποδός (podos), "foot". Most millipedes have very elongated cylindrical or flattened bodies with more than 20 segments, while pill millipedes are shorter and can roll into a ball, like a pillbug.

The name "millipede" is a compound word formed from the Latin roots mille ("thousand") and pes ("foot"). Despite their name, no known millipede has 1,000 legs, although the rare species Illacme plenipes has up to 750.[1] Common species have between 34 and 400 legs. There are approximately 12,000 named species classified into sixteen orders and around 140 families.[2] The longest extant species is the giant African millipede (Archispirostreptus gigas).

Most millipedes are slow-moving detritivores, eating decaying leaves and other dead plant matter. However, they can also be minor garden pests, especially in greenhouses where they can cause severe damage to emergent seedlings.

Millipedes can be easily distinguished from the somewhat similar and related centipedes (Class Chilopoda) which move rapidly, are carnivorous, and have a single pair of legs for each body segment. The scientific study of millipedes is known as diplopodology, and a scientist who studies them is called a diplopodologist.

Contents

  • Evolution 1
  • Characteristics 2
    • Head 2.1
    • Body 2.2
    • Internal organs 2.3
  • Reproduction and growth 3
  • Ecology 4
    • Habitat and distribution 4.1
    • Diet 4.2
    • Predators and parasites 4.3
    • Defence mechanisms 4.4
    • Other inter-species interactions 4.5
  • Interactions with people 5
  • Classification 6
    • Living groups 6.1
    • Fossil record 6.2
    • Outline of classification 6.3
  • See also 7
  • References 8
  • External links 9

Evolution

Millipedes are among the first animals to have colonised land during the Silurian geologic period. Early forms probably ate mosses and primitive vascular plants. There are two major groups of entirely extinct millipedes: the Archipolypoda ("ancient, many-legged ones") which contain the oldest known terrestrial animals, and Arthropleuridea, which contain the largest known land invertebrates. The oldest known land creature, Pneumodesmus newmani, was a 1 cm (0.39 in) long archipolypodan that lived 428 million years ago in the upper Silurian, and has clear evidence of spiracles (breathing holes) attesting to its air-breathing habits.[3][4] During the Upper Carboniferous (), Arthropleura became the largest known land invertebrate of all time, reaching lengths of up to 2.6 m (8 ft 6 in). Millipedes also include the earliest evidence of chemical defense, as some Devonian fossils have defensive gland openings called ozopores.[4] Millipedes, centipedes, and other terrestrial arthropods attained very large sizes in comparison to modern species in the oxygen-rich environments of the Devonian and Carboniferous periods, and some could grow larger than one metre. As oxygen levels lowered through time, arthropods became smaller in size.[5]

Characteristics

Representative body types of the Penicillata (top), Pentazonia (middle), and Helminthomorpha (bottom)
Anterior anatomy of a generalized helminthomorph milipede

Millipedes come in a variety of body shapes and sizes, ranging from 2 mm (0.079 in) to around 35 cm (14 in) in length,[6] and can have as few as eleven to over one hundred segments. They are generally black or brown in colour, although there are a few brightly coloured species.

Body styles vary greatly between major millipede groups. In the basal subclass Penicillata, consisting of the tiny bristle millipedes, the exoskelton is soft and uncalcified, and is covered in prominent setae or bristles. All other millipedes, belonging to the subclass Chilognatha, have a hardened exoskeleton. The chilognaths are in turn divided into two infraclasses: the Pentazonia, containing relatively short-bodied groups such as pill millipedes, and the Helminthomorpha ("worm-like" millipedes), which contains the vast majority of species, and the long, many-segmented body types familiar to most people.[7][8]

Head

The head of a millipede is typically rounded above and flattened below and bears a pair of large mandibles in front of a plate-like structure called a gnathochilarium ("jaw lip").[9]

The head contains a single pair of

  • Millipedes at the Encyclopedia of Life
  • Milli-PEET: The Class Diplopoda – The Field Museum, Chicago
  • Millipedes of North America in Myriapods: The World's Leggiest Animals
  • Millipedes of Australia
  • Diplopoda: Guide to New Zealand Soil Invertebrates - Massey University
  • SysMyr, a myriapod taxonomy database

External links

  1. ^ "Most leggy millipede rediscovered".  
  2. ^ a b c d e Shear, W. (2011). "Class Diplopoda de Blainville in Gervais, 1844. In: Zhang, Z.-Q. (Ed.) Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness".  
  3. ^ a b Wilson, Heather M.; Anderson, Lyall I. (2004). "Morphology and taxonomy of Paleozoic millipedes (Diplopoda: Chilognatha: Archipolypoda) from Scotland". Journal of Paleontology 78 (1): 169–184.  
  4. ^ a b c d e f g h i Shear, William A.; Edgecombe, Gregory D. (2010). "The geological record and phylogeny of the Myriapoda". Arthropod Structure & Development 39 (2–3): 174–190.  
  5. ^ Lockley, M. G.; Meyer, Christian (2013). "The tradition of tracking dinosaurs in Europe". Dinosaur Tracks and Other Fossil Footprints of Europe.  
  6. ^ a b Minelli, Alessandro; Golovatch, Sergei I. (2001). "Myriapods". In Levin, Simon A. Encyclopedia of Biodiversity. pp. 291–303.  
  7. ^ a b Bueno-Villegas, Julián; Sierwald, Petra; Bond, Jason E. "Diplopoda". In Bousquets, J. L.; Morrone, J. J. Biodiversidad, taxonomia y biogeografia de artropodos de Mexico. pp. 569–599. 
  8. ^ a b Shelley, Rowland M. "Millipedes". Retrieved October 12, 2013. 
  9. ^ a b c d e f g h i j k l m n o p q Sierwald, Petra; Bond, Jason E. (2007). "Current Status of the Myriapod Class Diplopoda (Millipedes): Taxonomic Diversity and Phylogeny".  
  10. ^ Lewis, J. G. E. (2008). The Biology of Centipedes (Digitally printed 1st paperback version. ed.). Cambridge:  
  11. ^ a b c d e f g Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 818–825.  
  12. ^ Capinera, John L., ed. (2008). "Millipedes". Encyclopedia of Entomology.  
  13. ^ Mesibov, Robert. "Paranota". External Anatomy of Polydesmida. Retrieved 30 October 2013. 
  14. ^ a b c d e Hopkin, Stephen P.; Read, Helen J. (1992). The Biology of Millipedes. Oxford: Oxford University Press.  
  15. ^ a b c d e Shelley, Rowland M. (1999). "Centipedes and Millipedes with Emphasis on North American Fauna". The Kansas School Naturalist 45 (3): 1–16. 
  16. ^ a b c d Blower, J. Gordon (1985). Millipedes: Keys and Notes for the Identification of the Species. London: Published for the Linnean Society of London and the Estuarine and Brackish-Water Sciences Association by  
  17. ^ Mesibov, Robert. "Gonopods". External Anatomy of Polydesmida. Retrieved 27 October 2013. 
  18. ^ Drago, Leandro; Fusco, Giuseppe; Garollo, Elena; Minelli, Alessandro (2011). "Structural aspects of leg-to-gonopod metamorphosis in male helminthomorph millipedes (Diplopoda)". Frontiers in Zoology 8 (1): 19.  
  19. ^ Wesener, Thomas; Köhler, Jörn; Fuchs, Stefan; van den Spiegel, Didier (2011). "How to uncoil your partner—"mating songs" in giant pill-millipedes (Diplopoda: Sphaerotheriida)". Naturwissenschaften 98 (11): 967–975.  
  20. ^ Enghoff, Henrik; Akkari, Nesrine (2011). "A callipodidan cocoon (Diplopoda, Callipodida, Schizopetalidae)". International Journal of Myriapodology 5: 49–53.  
  21. ^ Shelley, Rowland M.; Golavatch, and Sergei I. (2011). "Atlas of myriapod biogeography. I. Indigenous ordinal and supra-ordinal distributions in the Diplopoda: Perspectives on taxon origins and ages, and a hypothesis on the origin and early evolution of the class". Insecta Mundi 158: 1–134. 
  22. ^ a b Golovatch, Sergei I.; Kime., R. Desmond (2009). "Millipede (Diplopoda) distributions: a review.". Soil Organisms 81 (3): 565–597. 
  23. ^ Adis, Joachim (1986). "An 'aquatic' millipede from a Central Amazonian inundation forest".  
  24. ^ Burrows, F. J.; Hales, D. F.; Beattie, A. J. (1994). "Aquatic millipedes in Australia: a biological enigma and a conservation saga".  
  25. ^ Barber, A. D., ed. (2013). "World Database of Littoral Myriapoda".  
  26. ^ Barker, G. M. (2004). "Millipedes (Diplopoda) and Centipedes (Chilopoda)(Myriapoda) as predators of terrestrial gastropods". In Barker, G. M. Natural enemies of terrestrial molluscs. Wallingford, Oxfordshire, UK:  
  27. ^ Weldon, Paul J.; Cranmore, Catherine F.; Chatfield, Jenifer A. (2006). "Prey-rolling behavior of coatis (Nasua spp.) is elicited by benzoquinones from millipedes".  
  28. ^ Saporito, R. A.; Donnelly, M. A.; Hoffman, R. L.; Garraffo, H. M.; Daly, J. W. (2003). "A Siphonotid Millipede (Rhinotus) as the Source of Spiropyrrolizidine Oximes of Dendrobatid Frogs".  
  29. ^ Eisner, T.; Eisner, M.; Attygalle, A. B.; Deyrup, M.; Meinwald, J. (1998). "Rendering the inedible edible: circumvention of a millipede's chemical defense by a predaceous beetle larva.".  
  30. ^ Ito, F. (1998). "Colony composition and specialized predation on millipedes in the enigmatic ponerine ant genus Probolomyrmex (Hymenoptera, Formicidae)".  
  31. ^ Herbert, D. G. (2000). "Dining on diplopods: remarkable feeding behaviour in chlamydephorid slugs (Mollusca: Gastropoda)".  
  32. ^ Forgie, Shaun A.; Grebennikov, Vasily V.; Scholtz, Clarke H. (2002). Westwood, a millipede-eating genus of southern African dung beetles (Coleoptera : Scarabaeidae)"Sceliages"Revision of . Invertebrate Systematics 16 (6): 931–955.  
  33. ^ Larsen, T. H; Lopera, A.; Forsyth, A.; Genier, F. (2009). "From coprophagy to predation: a dung beetle that kills millipedes".  
  34. ^ Forthman, M., & Weirauch, C. (2012). "Toxic associations: A review of the predatory behaviors of millipede assassin bugs (Hemiptera: Reduviidae: Ectrichodiinae)". European Journal of Entomology 109 (2): 147–153.  
  35. ^  
  36. ^ Yasumasa Kuwahara; Hisashi Ômura; Tsutomu Tanabe (2002). "2-Nitroethenylbenzenes as natural products in millipede defense secretions".  
  37. ^ Weldon, Paul J.; Aldich, Jeffrey R.; Klun, Jerome A.; Oliver, James E.; Debboun, Mustapha (2003). "Benzoquinones from millipedes deter mosquitoes and elicit self-anointing in capuchin monkeys (Cebus spp.)".  
  38. ^ Valderrama, Ximena; Robinson, John G.; Attygalle, Athula B.; Eisner, Thomas (2000). "Seasonal anointment with millipedes in a wild primate: a chemical defense against insects".  
  39. ^ Birkinshaw, Christopher R. (1999). "Use of Millipedes by Black Lemurs to Anoint Their Bodies".  
  40. ^ Roncadori, R. W.; Duffey, S. S.; Blum, M. S. (1985). "Antifungal Activity of Defensive Secretions of Certain Millipedes".  
  41. ^ Eisner, Thomas; Eisner, Maria; Deyrup, Mark (1996). "Millipede defense: use of detachable bristles to entangle ants" ( 
  42. ^ Stoev, Pavel, & Lapeva-Gjonova, Albena (2005). "Myriapods from ant nests in Bulgaria (Chilopoda, Diplopoda)". Peckiana 4: 131–142. 
  43. ^ Farfan, Monica; Klompen, Hans (2012). "Phoretic mite associates of millipedes (Diplopoda, Julidae) in the northern Atlantic region (North America, Europe)". International Journal of Myriapodology 7: 69.  
  44. ^ Swafford, Lynn; Bond, Jason E. (2010). "Failure to cospeciate: an unsorted tale of millipedes and mites". Biological Journal of the Linnean Society 101 (2): 272–287.  
  45. ^ Martínez-Torres, Shirley Daniella; Daza, Álvaro Eduardo Flórez; Linares-Castillo, Edgar Leonardo (2011). "Meeting between kingdoms: discovery of a close association between Diplopoda and Bryophyta in a transitional Andean-Pacific forest in Colombia". International Journal of Myriapodology 6: 29.  
  46. ^ Marshall, Michael (22 September 2011). "Zoologger: Stealth millipede wears living camouflage". New Scientist. 
  47. ^ Mason, G.; Thompson, H.; Fergin, P.; Anderson, R. (1994). "Spot diagnosis: the burning millipede".  
  48. ^ Shpall, S.; Frieden, I. (1991). "Mahogany discoloration of the skin due to the defensive secretion of a millipede". Pediatric Dermatology 8 (1): 25–27.  
  49. ^ Radford, A. (1976). "Giant millipede burns in Papua New Guinea". Papua New Guinea Medical Journal 18 (3): 138–141.  
  50. ^ Radford, A. (1975). "Millipede burns in man". Tropical and Geographical Medicine 27 (3): 279–287.  
  51. ^ Hudson, B.; Parsons, G. (1997). "Giant millipede 'burns' and the eye".  
  52. ^ Alagesan, P.; Muthukrishnan, J. (2005). (Fabricius, 1775)"Xenobolus carnifex"Bioenergetics of the household pest, . Peckiana 4: 3–14. 
  53. ^ Enghoff, Henrik; Kebapći, Ümit (2008). "Calyptophyllum longiventre (Verhoeff, 1941) invading houses in Turkey, with the first description of the male (Diplopoda: Julida: Julidae)".  
  54. ^ Ebregt, E.; Struik, P. C.; Odongo, B.; Abidin, P. E. (2005). "Pest damage in sweet potato, groundnut and maize in north-eastern Uganda with special reference to damage by millipedes (Diplopoda)". NJAS – Wageningen Journal of Life Sciences 53 (1): 49–69.  
  55. ^ Keiko Niijima (2001). , Koch) stopped trains]Oxidus gracilisヤケヤスデ列車を止める [A millipede outbreak (. Edaphologia (in Japanese) (68): 43–46.  
  56. ^ Peckham, Matt (Sep 4, 2013). "Millipedes – Yes, Millipedes – May Be Responsible for Australian Train Crash". Time Newsfeed.  
  57. ^ Stoev, Pavel; Zapparoli, Marzio; Golovatch, Sergei; Enghoff, Henrik; Akkari, Nesrine; Barber, Anthony (2010). (Eds). Alien terrestrial arthropods of Europe"et al. Roques In:"Myriapods (Myriapoda). Chapter 7.2. . BIORISK – Biodiversity and Ecosystem Risk Assessment 4: 97–130.  
  58. ^ Lewbart, Gregory A. (ed.). Invertebrate Medicine (2nd ed.). Chichester, West Sussex:  
  59. ^ a b c Costa Neto, Eraldo M. (2007). "The perception of Diplopoda (Arthropoda, Myriapoda) by the inhabitants of the county of Pedra Branca, Santa Teresinha, Bahia, Brazil". Acta Biológica Colombiana 12 (2): 123–134. 
  60. ^ Lawal, O. A.; Banjo, A. D. (2007). "Survey for the Usage of Arthropods in Traditional Medicine in Southwestern Nigeria". Journal of Entomology 4 (2): 104–112.  
  61. ^ Negi, C. S.; Palyal, V. S. (2007). "Traditional Uses of Animal and Animal Products in Medicine and Rituals by the Shoka Tribes of District Pithoragarh, Uttaranchal, India". Studies on Ethno-Medicine 1 (1): 47–54. 
  62. ^ Jiang, TL; Feng, GW; Shen, JH; Li, LF; Fu, XQ (1981). "Observation of the effect of Spirobolus bungii extract on cancer cells.". Journal of traditional Chinese medicine = 1 (1): 34–8.  
  63. ^ Enghoff, Henrik; Manno, Nicola; Tchibozo, Sévérin; List, Manuela; Schwarzinger, Bettina; Schoefberger, Wolfgang; Schwarzinger, Clemens; Paoletti, Maurizio G. (2014). "Millipedes as Food for Humans: Their Nutritional and Possible Antimalarial Value—A First Report". Evidence-Based Complementary and Alternative Medicine 2014: 1–9.  
  64. ^ Coelho, Joseph R. (2011). "Noninsect Arthropods in Popular Music". Insects 2 (4): 253–263.  
  65. ^ Avirovik, Dragan; Butenhoff, Bryan; Priya, Shashank (2014). "Millipede-inspired locomotion through novel U-shaped piezoelectric motors". Smart Materials and Structures 23 (3): 037001.  
  66. ^ Wakimoto, Shuichi; Suzumori, Koichi; Kanda, Takefumi (2006). "A bio-mimetic amphibious soft cord robot". Nihon Kikai Gakkai Ronbunshu, C Hen/Transactions of the Japan Society of Mechanical Engineers, Part C (in Japanese with English abstract) 72 (2): 471–477. 
  67. ^ Beattie, Andrew; Ehrlich, Paul (2001). Wild Solutions: How Biodiversity is Money in the Bank (2nd ed.). New Haven: Yale University Press. pp. 192–194.  
  68. ^ a b Brewer, Michael S.; Sierwald, Petra; Bond, Jason E. (2012). "Millipede Taxonomy after 250 Years: Classification and Taxonomic Practices in a Mega-Diverse yet Understudied Arthropod Group". PLoS ONE 7 (5): e37240.  
  69. ^ Caroli Linnaei (1758). Systema naturae per regna tria naturae: secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. pp. 639–640. 
  70. ^ Shelley, R. M. (2007). "Taxonomy of extant Diplopoda (Millipeds) in the modern era: Perspectives for future advancements and observations on the global diplopod community (Arthropoda: Diplopoda)". Zootaxa 1668: 343–362. 
  71. ^ Shelley, Rowland M.; Petra Sierwald; Selena B. Kiser; Sergei I. Golovatch (2000). Nomenclator generum et familiarum Diplopodorum II : a list of the genus and family-group names in the class Diplopoda from 1958 through 1999. Sofia, Bulgaria: Pensoft. p. 5.  
  72. ^ Hoffman, Richard L. (1980). Classification of the Diplopoda. Geneva, Switzerland: Muséum d’Historie Naturelle. pp. 1–237. 
  73. ^ Enghoff, H. (1984). "Phylogeny of millipedes - a cladistic analysis". Journal of Zoological Systematics and Evolutionary Research 22 (1): 8–26.  
  74. ^ Wilson, Heather M.; Shear, William A. (2000). "Microdecemplicida, a new order of minute arthropleurideans (Arthropoda: Myriapoda) from the Devonian of New York State, U.S.A.". Transactions of the Royal Society of Edinburgh: Earth Sciences 90 (04): 351–375.  
  75. ^ a b Kraus, O.; Brauckmann, C. (2003). "Fossil giants and surviving dwarfs. Arthropleurida and Pselaphognatha (Atelocerata, Diplopoda): characters, phylogenetic relationships and construction". Verhandlungen des Naturwissenschaftlichen Vereins in Hamburg 40: 5–50. 
  76. ^ Kraus, O. (2005). "On the structure and biology of Arthropleura species (Atelocerata, Diplopoda; Upper Carboniferous/Lower Permian)". Verhandlungen des Naturwissenschaftlichen Vereins in Hamburg 41: 5–23. 
  77. ^ Hoffman, R.L. (1963). "New genera and species of Upper Paleozoic Diplopoda".  

References

See also

Class Diplopoda de Blainville in Gervais, 1844

The higher-level classification of millipedes is presented below, based on Shear, 2011,[2] and Shear & Edgecombe, 2010[4] (extinct groups). Recent cladistic and molecular studies have challenged the traditional classification schemes, above and in particular the position of the orders Siphoniulida and Polyzoniida is not yet well established.[9] The placement and positions of extinct groups (†) known only from fossils is tentative and not fully resolved.[4][9] After each name is listed the author citation: the name of the person who coined the name or defined the group, even if not at the current rank.

Outline of classification

Diplopoda
Penicillata Polyxenida

Chilognatha
Arthropleuridea

Arthropleurida


Eoarthropleurida


Microdecemplicida



Pentazonia Amynilyspedida

Helminthomorpha
Archipolypoda

Archidesmida


Cowiedesmida


Euphoberiida


Palaeosomatida




Pleurojulida


Colobognatha

Eugnatha


Nematophora


Polydesmida


Juliformia

Julida


Spirobolida


Spirostreptida


Xyloiuloidea








Reconstruction of Arthropleura, a giant millipede of the late Paleozoic

Penicillata
Arthropleuridea

Arthropleurida


Eoarthropleurida



Polyxenida




Microdecemplicida


Chilognatha



Alternate hypothesis of fossil relationships [9][75]

In addition to the 16 living orders, there are 9 extinct orders and one superfamily known only from fossils. The relationship of these to living groups and to each other is controversial. The extinct Arthropleuridea was long considered a distinct myriapod class, although work in the early 21st century established the group as a subclass of millipedes.[74][75][76] Several living orders also appear in the fossil record. Below are two proposed arrangements of fossil millipede groups.[4][9] Extinct groups are indicated with a dagger (†). The extinct order Zosterogrammida, a chilognath of uncertain position,[4] is not shown.

Fossil record

Diplopoda
Penicillata

Polyxenida


Chilognatha
Pentazonia
Limacomorpha Glomeridesmida

Oniscomorpha

Glomerida


Sphaerotheriida



Helminthomorpha
Colobognatha

Platydesmida


Siphonocryptida


Polyzoniida


Siphonophorida


Eugnatha
Nematophora

Chordeumatida


Callipodida


Stemmiulida


Merochaeta

Polydesmida


Juliformia

Julida


Spirobolida


Spirostreptida



Siphoniulida





In 1971, Dutch biologist C. A. W. Jeekel published a comprehensive listing of all known millipede genera and families described between 1758 and 1957 in his Nomenclator Generum et Familiarum Diplopodorum, a work credited as launching the "modern era" of millipede taxonomy.[70][71] In 1980, American biologist Richard L. Hoffman published a classification of millipedes which recognized the the Penicillata, Pentazonia, and Helminthomorpha,[72] and the first phylogenetic analysis of millipede orders using modern cladistic methods was published in 1984 by Henrik Enghoff of Denmark.[73] A 2003 classification by American myriapodologist Rowland Shelley is similar to classification originally proposed by Verhoeff, and remains the currently accepted classification scheme (shown below), despite more recent molecular studies which propose a number of conflicting relationships.[4][9] A 2011 summary of millipede family diversity by William A. Shear placed the order Siphoniulida within the larger group Nematomorpha.[2]

The history of scientific millipede classification began with Carl Linnaeus, who in his 10th edition of Systema Naturae, 1758, named seven species of Julus as "Insecta Aptera" (wingless insects).[69] In 1802, the French zoologist Pierre André Latreille proposed the name Chilognatha as the first group of what are now the Diplopoda, and in 1840 the German naturalist Johann Friedrich von Brandt produced the first detailed classification. The name Diplopoda itself was coined in 1844 by Henri Marie Ducrotay de Blainville. In the following decades, millipede taxonomy was driven by relatively few researchers at any given time, with major contributions by Carl Attems, Karl Verhoeff and Ralph V. Chamberlin, who each described over 1,000 species, as well as Orator F. Cook, Filippo Silvestri, R. I. Pocock, and Henry W. Brölemann.[9] The 50-year period from 1890 to 1940, when the seven researchers above were working, was a period when the science of diplopodology flourished: rates of species descriptions during this period was on average the highest in history, sometimes exceeding 300 per year.[68]

Living groups

The living members of the Diplopoda are divided into sixteen orders in two subclasses.[2] The basal subclass Penicillata contains a single order, Polyxenida (bristle millipedes). All other millipedes belong to the subclass Chilognatha consisting of two infraclasses: the infraclass Pentazonia containing the short-bodied pill millipedes, and the infraclass Helminthomorpha (worm-like millipedes) containing the great majority of the species.[7][8]

The science of millipede biology and taxonomy is called diplopodology: the study of diplopods. Approximately 12,000 millipede species have been described, but estimates of the true number of species on earth range from 15,000–20,000[68] to as high as 80,000.[9]

Approximate relative diversity of extant millipede orders, ranging from ca. 3,500 species of Polydesmida to 2 species of Siphoniulida.[2]

Classification

[14] In biology, some authors have advocated millipedes as [67] in particular when heavy loads are needed to be carried in tight areas involving turns and curves.[66][65] Millipedes have also inspired and played roles in scientific research. The locomotion and anatomy of millipedes have inspired the design of experimental robots,

Millipedes also appear in folklore and traditional medicine around the world. Many cultures ascribe millipede activity with coming rains.[59] In the Yoruba culture of Nigeria, millipedes are used in pregnancy and business rituals, and crushed millipedes are used to treat fever, whitlow, and convulsion in children.[60] In Zambia, smashed millipede pulp is used to treat wounds, and in the Bafia people of Cameroon millipede juice is used to treat earaches.[59] In certain Himalayan Bhotiya tribes, dry millipede smoke is used to treat hemorrhoids.[61] Native people in Malaysia use millipede secretions in poison-tipped arrows.[59] The secretions of Spirobolus bungii have even been reported to inhibit division of human cancer cells.[62] The only reported usage of millipedes as food by humans comes from the Bobo people of Burkina Faso, who consume boiled, dried millipedes in tomato sauce.[63] In popular music (including names of albums, songs, and artists) millipedes are poorly represented compared to other arthropods.[64]

Some of the larger millipedes in the orders Spirobolida, Spirostreptida, and Sphaerotheriida are popular as pets.[57] Some species commonly sold or kept include species of Archispirostreptus, Aphistogoniulus, Narceus, and Orthoporus.[58]

Some millipedes are considered household pests, including Xenobolus carnifex which can infest thatched roofs in India,[52] and Ommatoiulus moreleti, which periodically invades homes in Australia. Other species exhibit periodical swarming behaviour, which can result in home invasions,[53] crop damage,[54] train delays, or even train crashes and derailments when the tracks become slippery with the crushed remains of thousands of millipedes.[14][55][56] Some millipedes can cause significant damage to crops: the spotted snake millipede (Blaniulus guttulatus) is a noted pest of sugar beets and other root crops, and as a result is one of the few millipedes with a common name.[16]

An aggregation of millipedes

Millipedes generally have little impact to human economic or social well-being, especially in comparison with insects, although locally can be a nuisance or agricultural pest. Millipedes do not bite, and their defensive secretions are mostly harmless to humans – usually causing only minor discoloration on the skin – but the secretions of some tropical species may cause pain, itching, local erythema, edema, blisters, eczema, and occasionally cracked skin.[47][48][49][50] Eye exposures to these secretions causes general irritation and potentially more severe effects such as conjunctivitis and keratitis.[51] First aid consists of flushing the area thoroughly with water; further treatment is aimed at relieving the local effects.

Interactions with people

A novel interaction between millipedes and mosses was described in 2011, in which individuals of the newly discovered Psammodesmus bryophorus was found to have up to ten species living on its dorsal surface, in what may provide camouflage for the millipede and increased dispersal for the mosses.[45][46]

Many millipede species have commensal relationships with mites of the orders Mesostigmata and Astigmata. Many of these mites are believed to be phoretic rather than parasitic, which means they simply use the millipede host as a means of dispersal.[43][44]

Some millipedes form commensal relationships, in which only one species benefits while the other is unaffected. Several species form close relationships with ants, a relationship known as myrmecophily, especially within the family Pyrgodesmidae (Polydesmida), which contains "obligate myrmecophiles"- species which have only been found in ant colonies. More species are "facultative myrmecophiles", being non-exclusively associated with ants, including many species of Polyxenida that have been found in ant nests around the world.[42]

Psammodesmus bryophorus camouflaged with symbiotic mosses

Other inter-species interactions

Due to their lack of speed and their inability to bite or sting, millipedes' primary defence mechanism is to curl into a tight coil – protecting their delicate legs inside an armoured exoskeleton. Many species also emit various foul-smelling liquid secretions through microscopic holes called ozopores (the openings of "odoriferous" or "repugantorial glands"), along the sides of their bodies as a secondary defence. These secretions may include alkaloids, benzoquinones, phenols, terpenoids, and/or hydrogen cyanide, among many others.[35][36] Some of these substances are caustic and can burn the exoskeleton of ants and other insect predators, and the skin and eyes of larger predators. Primates such as capuchin monkeys and lemurs have been observed intentionally irritating millipedes in order to rub the chemicals on themselves to repel mosquitoes.[37][38][39] Some of these defensive compounds also show antifungal activity.[40] The bristly millipedes (order Polyxenida) lack both an armoured exoskeleton and odiferous glands, and instead are covered in numerous bristles that in at least one species, Polyxenus fasciculatus, detach and entangle ants.[41]

Ammodesmus nimba from Guinea, West Africa, curled in a defensive coil

Defence mechanisms

Parasites of millipedes include nematodes, phaeomyiid flies, and acanthocephalans.[9]

Millipedes are preyed upon by a wide range of animals, including various reptiles, amphibians, birds, mammals, and insects.[9] Mammalian predators such as [32][33] A large subfamily of assassin bugs, the Ectrichodiinae with over 600 species, has specialized in preying upon millipedes.[34]

A Sceliages beetle transporting a millipede carcass

Predators and parasites

[15] Some species have piercing mouth parts that allow them to feed on plant juices.[26][11].snails, or earthworms or occasionally carnivorous, feeding on insects, centipedes, omnivorous A few species are [9] feed on fungi.Platydesmida graze algae from bark, and Polyxenida Some millipedes are herbivorous, feeding on living plants, and some species can become serious pests of crops. Millipedes in the order [14] The majority of millipedes are

Diet

Millipedes occur on all continents except Antarctica, and occupy almost all terrestrial habitats, ranging as far north as the Arctic Circle in Iceland, Norway, and Central Russia, and as far south as Santa Cruz Province, Argentina.[21][22] Millipedes are typically forest floor dwellers, occurring leaf litter, dead wood, or soil, with a preference for humidity. In temperate zones, millipedes are most abundant in moist deciduous forests, and may reach densities of over 1,000 individuals per square meter. Other habitats include coniferous forests, deserts, caves, and alpine ecosystems.[15][22] Some species can survive freshwater floods and live submerged underwater for up to 11 months.[23][24] A few species occur near the seashore and can survive in somewhat salty conditions.[16][25]

Habitat and distribution

Ecology

The young hatch after a few weeks, and typically have only three pairs of legs, followed by up to four legless segments. As they grow, they continually moult, adding further segments and legs as they do so. Some species moult within specially prepared chambers of soil or silk,[20] which they may also use to wait out dry weather, and most species eat the shed exoskeleton after moulting. The adult stage- when individuals become reproductively mature- is generally reached in the final molt stage, which varies between species and orders, although some species continue to molt after adulthood. Furthermore, some species alternate between reproductive and non-reproductive stages after maturity, a phenomenon known as periodomorphosis, in which the reproductive structures regress during non-reproductive stages.[16] Millipedes may live from one to ten years, depending on species.[11]

Females lay between ten and three hundred eggs at a time, depending on species, fertilising them with the stored sperm as they do so. Many species simply deposit the eggs on moist soil or organic detritus, but some construct nests lined with dried faeces, and may protect the eggs within silk cocoons.[11] In most species the female abandon the eggs after laying but some species in the orders Platydesmida and Stemmiulida provide parental care for eggs and young.[15]

In all millipedes except the bristle millipedes, copulation occurs with the two individuals facing one another. Copulation may be preceded by male behaviors such as tapping with antennae, running along the back of the female, offering glandular secretions which the female consumes, or in the case of some pill-millipedes, stridulation or "chirping".[19] During copulation in most millipedes, the male positions his seventh segment in front of the female's third segment, and may insert his gonopods to extrude the vulvae before bending his body to deposit sperm onto his gonopods and reinserting the "charged" gonopods into the female.[14]

The genital openings (gonopores) of both sexes are located on the underside of the third body segment (near the second pair of legs) and may be accompanied in the male by one or two penes which deposit the sperm packets onto the gonopods. In the female, the genital pores open into paired small sacs called cyphopods or vulvae, which are covered by a small hood-like cover, and are used to store the sperm after copulation.[11] The cyphopod morphology can also be used to identify species. Millipede sperm is aflagellate (lacks a flagellum), a unique trait among myriapods.[9]

Growth stages of Nemasoma (Nemasomatidae), which reaches reproductive maturity in stage V

Gonopods occur in a diversity of shapes and sizes, and in the range from closely resembling walking legs to complex structures quite unlike legs at all. In some groups the gonopods are kept retracted within the body, while in others they project forward parallel to the body. Gonopod morphology is the predominant means of determining species among millipedes: the structures may differ greatly between closely related species but very little within a species.[17] The gonopods develop gradually from walking legs through successive moults until reproductive maturity.[18]

The gonopods of Nipponesmus shirinensis are quite unlike walking legs.
Left gonopod of Oxidus gracilis. False color SEM image, scale bar: 0.2 mm

Millipedes show a diversity of mating styles and structures. In the basal order Polyxenida (bristle millipedes), mating is indirect: males deposit spermatophores onto webs they secrete with special glands, and the spermatophores are subsequently picked up by females.[15] In all other millipede groups, males possess one or two pairs of modified legs called gonopods which are used to transfer sperm to the female during copulation. The location of the gonopods differs between groups: in males of the Pentazonia they are located at the rear of the body and known as telopods and may also function in grasping females, while in the Helminthomorpha – the vast majority of species – they are located on the seventh body segment.[9] A few species are parthenogenetic, having few, if any, males.[16]

Epibolus pulchripes mating; the male is at right

Reproduction and growth

Millipedes breathe through two pairs of malpighian tubules, located near the mid-part of the gut. The digestive tract is a simple tube with two pairs of salivary glands to help digest the food.[11]

Internal organs

The legs are composed of seven segments, and attach on the underside of the body. The legs of an individual are generally rather similar to each other, although often longer in males than females, and males of some species have a reduced or enlarged first pair of legs.[14] The most conspicuous leg modifications are involved in reproduction, and are discussed below.

Millipedes in several orders have keel-like extensions of the body-wall known as paranota, which can vary widely in shape, size, and texture. Paranota may allow millipedes to wedge more securely into crevices, protect the legs, or make the millipede more difficult for predators to swallow.[13]

The first segment behind the head is legless and known as a collum (from the Latin for neck or collar). The second, third, and fourth body segments bear a single pair of legs each and are known as "haplosegments", from the Greek haplo, "single" (the three haplosegments are sometimes referred to as a "thorax"[3]). The remaining segments, from the fifth to the posterior, are properly known as diplosegments or double segments. Each diplosegment bears two pairs of legs, rather than just one as in centipedes. This is because each diplosgment is formed by the fusion of two embryonic segments. In some millipedes the last few segments may be legless. The terms "segment" or "body ring" are often used interchangeably to refer to both haplo- and diplosegments. The final segment is known as the telson, which consists of a legless preanal ring, a pair of anal valves (closeable plates around the anus), and a small scale below the anus.[9][11]

Millipede bodies may be flattened or cylindrical, and are composed of numerous metemeric segments, each with an exoskeleton consisting of five chitinous plates: a single plate above (the tergite), one at each side (pleurites), and a plate on the underside (sternite) where the legs attach. In many millipedes, these plates are fused to varying degrees, sometimes forming a single cylindrical ring. The plates are typically hard, being impregnated with calcium salts.[11] Because they lack a waxy cuticle, millipedes are susceptible to water loss and must spend most of their time in moist or humid environments.[12]

Paranota of polydesmidan (left) and platydesmidan millipedes

Body

Millipede eyes consist of a number of simple flat-lensed ocelli arranged in a group or patch on each side of the sides of the head. These patches are also called ocular fields or ocellaria. Many species of millipedes, including the entire order Polydesmida and cave-dwelling millipedes such as Causeyella and Trichopetalum, have secondarily lost their eyes and are completely blind.[6]

[10], and are possibly used to measure humidity or light levels in the surrounding environment.centipedes but they also occur in some [9]

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