Millipedes Of Central America
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Millipedes are a group of arthropods that are characterised by having two pairs of jointed
legs A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element ...
on most body segments; they are known scientifically as the
class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...
Diplopoda, the name derived from this feature. Each double-legged segment is a result of two single segments fused together. Most millipedes have very elongated cylindrical or flattened bodies with more than 20 segments, while pill millipedes are shorter and can roll into a tight ball. Although the name "millipede" derives from the Latin for "thousand feet", no species was known to have 1,000 or more until the discovery of '' Eumillipes persephone'', which can have over 1,300 legs. There are approximately 12,000 named species classified into 16
orders Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
and around 140 families, making Diplopoda the largest class of myriapods, an arthropod group which also includes
centipede Centipedes (from New Latin , "hundred", and Latin , " foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', lip, and New Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, an ...
s and other multi-legged creatures. Most millipedes are slow-moving
detritivore Detritivores (also known as detrivores, detritophages, detritus feeders, or detritus eaters) are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). There are many kinds of invertebrates, ...
s, eating decaying leaves and other dead plant matter. Some eat fungi or drink plant fluids, and a small number are predatory. Millipedes are generally harmless to humans, although some can become household or garden
pests PESTS was an anonymous American activist group formed in 1986 to critique racism, tokenism, and exclusion in the art world. PESTS produced newsletters, posters, and other print material highlighting examples of discrimination in gallery represent ...
. Millipedes can be an unwanted nuisance particularly in
greenhouse A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of Transparent ceramics, transparent material, such as glass, in which plants requiring regulated climatic condit ...
s where they can potentially cause severe damage to emergent seedlings. Most millipedes defend themselves with a variety of chemicals secreted from pores along the body, although the tiny bristle millipedes are covered with tufts of detachable bristles. Its primary defence mechanism is to curl into a tight coil, thereby protecting its legs and other vital delicate areas on the body behind a hard exoskeleton.
Reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual or ...
in most species is carried out by modified male legs called gonopods, which transfer packets of sperm to females. First appearing in the
Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...
period, millipedes are some of the oldest known land animals. Some members of prehistoric groups, such as '' Arthropleura'', grew to over ; the largest modern species reach maximum lengths of . The longest extant species is the giant African millipede ('' Archispirostreptus gigas''). Among myriapods, millipedes have traditionally been considered most closely related to the tiny pauropods, although some molecular studies challenge this relationship. Millipedes can be distinguished from the somewhat similar but only distantly related
centipede Centipedes (from New Latin , "hundred", and Latin , " foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', lip, and New Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, an ...
s (class Chilopoda), which move rapidly, are venomous,
carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...
, and have only a single pair of legs on each body segment. The scientific study of millipedes is known as diplopodology, and a scientist who studies them is called a diplopodologist.


Etymology and names

The term "millipede" is widespread in popular and scientific literature, but among North American scientists, the term "milliped" (without the terminal e) is also used.
Other vernacular names include "thousand-legger" or simply "diplopod". The science of millipede biology and taxonomy is called diplopodology: the study of diplopods.


Classification

Approximately 12,000 millipede species have been described. Estimates of the true number of species on earth range from 15,000 to as high as 80,000. Few species of millipede are at all widespread; they have very poor dispersal abilities, depending as they do on terrestrial locomotion and humid habitats. These factors have favoured genetic isolation and rapid
speciation Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within ...
, producing many lineages with restricted ranges. The living members of the Diplopoda are divided into sixteen orders in two subclasses. The basal subclass Penicillata contains a single order, Polyxenida (bristle millipedes). All other millipedes belong to the subclass Chilognatha consisting of two infraclasses: Pentazonia, containing the short-bodied pill millipedes, and Helminthomorpha (worm-like millipedes), containing the great majority of the species.


Outline of classification

The higher-level classification of millipedes is presented below, based on Shear, 2011, and Shear & Edgecombe, 2010 (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. The placement and positions of extinct groups (†) known only from fossils is tentative and not fully resolved. 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. Class Diplopoda de Blainville in Gervais, 1844 * Subclass Penicillata Latreille, 1831 ** Order Polyxenida Verhoeff, 1934 * Subclass † Arthropleuridea (placed in Penicillata by some authors) **Order † Arthropleurida Waterlot, 1934 ** Order † Eoarthropleurida Shear & Selden, 1995 ** Order † Microdecemplicida Wilson & Shear, 2000 * Subclass Chilognatha Latreille, 1802 ** Order †
Zosterogrammida Zosterogrammidae is an extinct family of millipedes containing three genera, each with a single species. Fossils are known from the Czech Republic, Scotland, and the USA. Zosterogrammidae constitutes the sole family of the order Zosterogrammida ...
Wilson, 2005 (Chilognatha '' incertae sedis'') ** Infraclass
Pentazonia Pentazonia is a taxonomic infraclass of millipedes containing the pill-millipedes (Oniscomorpha) which can roll into a ball and the order Glomeridesmida which cannot. Defining traits (apomorphies) include divided sternites, a labrum with single ...
Brandt, 1833 *** Order †
Amynilyspedida Pill millipedes are any members of two living (and one extinct) Order (biology), orders of millipedes, often grouped together into a single superorder, Oniscomorpha. The name Oniscomorpha refers to the millipedes' resemblance to certain woodlouse ...
Hoffman, 1969 *** Superorder
Limacomorpha Glomeridesmida is an order of millipedes in the infraclass Pentazonia containing 2 families and at least 31 species. Glomeridesmida is the only living order of the superorder Limacomorpha. Glomeridesmidans are small (less than ) and somewhat f ...
Pocock, 1894 **** Order Glomeridesmida Cook, 1895 *** Superorder
Oniscomorpha Pill millipedes are any members of two living (and one extinct) Order (biology), orders of millipedes, often grouped together into a single superorder, Oniscomorpha. The name Oniscomorpha refers to the millipedes' resemblance to certain woodlouse ...
Pocock, 1887 **** Order
Glomerida Glomerida is an order of pill-millipedes found primarily in the Northern Hemisphere. They superficially resemble pill-bugs or woodlice, and can enroll into a protective ball. They have twelve body segments, 17 to 19 pairs of legs, and males hav ...
Brandt, 1833 **** Order
Sphaerotheriida Sphaerotheriida is an order of millipedes in the infraclass Pentazonia, sometimes known as giant pill millipedes. They inhabit Southern Africa, Madagascar, South and Southeast Asia, Australia and New Zealand. Like the Northern Hemisphere pill m ...
Brandt, 1833 ** Infraclass Helminthomorpha Pocock, 1887 *** Superorder †
Archipolypoda Archipolypoda is an extinct group of millipedes known from fossils in Europe and North America and containing the earliest known land animals. The Archipolypoda was erected by Scudder (1882) but redefined in 2005 with the description of sever ...
Scudder, 1882 **** Order †
Archidesmida The Archidesmida is an extinct order (biology), order of millipedes known from fossils from the Devonian period of Europe and North America. Archidesmidans have broad flat keels (paranota) extending from their body segments, and a modified pair o ...
Wilson & Anderson 2004 **** Order † Cowiedesmida Wilson & Anderson 2004 **** Order †
Euphoberiida Euphoberiidae is an extinct family of archipolypodan millipedes known from the Upper Pennsylvanian of Europe and North America. The family includes relatively large millipedes measuring up to long bearing distinctive spines and were the dominan ...
Hoffman, 1969 **** Order †
Palaeosomatida ''Palaeosoma'' is an extinct genus of archipolypodan millipedes from the upper Carboniferous of England and Poland. Individuals grew to nearly long and possessed defensive glands ( ozopores) located on small raised nodes on the outer edges of ...
Hannibal & Krzeminski, 2005 *** Order †
Pleurojulida Pleurojulidae is an extinct family of millipedes known from the Westphalian stage of the upper Carboniferous that are distinct enough to be placed in their own order, Pleurojulida. Fossil pleurojulids up to 10 centimeters long are known from Eur ...
Schneider & Werneburg, 1998 (possibly sister to Colobognatha) *** Subterclass
Colobognatha Colobognatha is a clade (formally considered a subterclass) of helminthomorph millipedes containing four orders: Platydesmida, Polyzoniida, Siphonocryptida, and Siphonophorida. Description The Colobognatha are united by several shared traits ( ...
Brandt, 1834 **** Order
Platydesmida Platydesmida (Greek for ''platy'' "flat" and ''desmos'' "bond") is an order of millipedes containing two families and over 60 species. Some species practice paternal care, in which males guard the eggs. Description Platydesmidans have a flatte ...
Cook, 1895 **** Order
Polyzoniida __NOTOC__ Polyzoniida is an order of millipedes in the Class_(biology)#Hierarchy_of_ranks_below_and_above_the_level_of_class, subterclass Colobognatha containing three families and at least 74 described species. Description Polyzoniidans have a ...
Cook, 1895 **** Order Siphonocryptida Cook, 1895 **** Order
Siphonophorida Siphonophorida (Greek language, Greek for "tube bearer") is an order of millipedes containing two families and over 100 species. Description Millipedes in the order Siphonophorida are long and worm-like, reaching up to in length and up to 190 ...
Newport, 1844 *** Subterclass Eugnatha Attems, 1898 **** Superorder Juliformia Attems, 1926 ***** Order Julida Brandt, 1833 ***** Order
Spirobolida Spirobolida is an order of "round-backed" millipedes containing approximately 500 species in 12 families. Its members are distinguished by the presence of a "pronounced suture that runs "vertically down the front of the head". Most of the spec ...
Cook, 1895 ***** Order
Spirostreptida Spirostreptida is an order (biology), order of long, cylindrical millipedes. There are approximately 1000 described species, making Spirostreptida the third largest order of millipedes after Polydesmida and Chordeumatida. Description Spirostrept ...
Brandt, 1833 *****Superfamily †
Xyloiuloidea Xyloiuloidea is an extinct superfamily of millipedes that existed from the Lower Devonian through the Upper Pennsylvanian period in Europe and North America. Description Xyloiuloids are more or less cylindrical, with sternites, pleurites, and ...
Cook, 1895 (Sometimes aligned with Spirobolida) **** Superorder Nematophora Verhoeff, 1913 ***** Order Callipodida Pocock, 1894 ***** Order Chordeumatida Pocock 1894 ***** Order
Stemmiulida Stemmiulida is an order of millipedes consisting of approximately 130 species, reaching up to 50 mm in length. It contains a single family, Stemmiulidae. Description Stemmiulids are small to medium sized millipedes, reaching a maximum leng ...
Cook, 1895 ***** Order Siphoniulida Cook, 1895 **** Superorder Merocheta Cook, 1895 ***** Order Polydesmida Pocock, 1887


Evolution

Millipedes are among the first animals to have colonised land during the Silurian period. Early forms probably ate
moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...
es and primitive vascular plants. There are two major groups of millipedes whose members are all extinct: the
Archipolypoda Archipolypoda is an extinct group of millipedes known from fossils in Europe and North America and containing the earliest known land animals. The Archipolypoda was erected by Scudder (1882) but redefined in 2005 with the description of sever ...
("ancient, many-legged ones") which contain the oldest known terrestrial animals, and Arthropleuridea, which contain the largest known land invertebrates. The earliest known land creature, '' Pneumodesmus newmani'', was an archipolypodan known from long fragment that lived 414 million years ago in the early
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...
, and has clear evidence of
spiracle Spiracle or spiraculum may refer to: * Spiracle (arthropods), opening in the exoskeletons of some arthropods * Spiracle (vertebrates), openings on the surface of some vertebrates * Spiraculum, a genus of land snails in family Cyclophoridae Cycl ...
s (breathing holes) attesting to its air-breathing habits. During the Upper
Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...
(), '' Arthropleura'' became the largest known land-dwelling invertebrate on record, reaching lengths of at least . Millipedes also exhibit the earliest evidence of chemical defence, as some
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...
fossils have defensive gland openings called ozopores. 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.


Living groups

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). 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 Johann Friedrich von Brandt (25 May 1802 – 15 July 1879) was a German-Russian natural history, naturalist, who worked mostly in Russia. Brandt was born in Jüterbog and educated at a Gymnasium (school), gymnasium in Wittenberg and the Humboldt ...
produced the first detailed classification. The name Diplopoda itself was coined in 1844 by the French zoologist Henri Marie Ducrotay de Blainville. From 1890 to 1940, millipede taxonomy was driven by relatively few researchers at any given time, with major contributions by
Carl Attems Carl August Graf Attems-Petzenstein (13 October 1868 in Graz, Austria – 19 April 1952 in Vienna) was an Austrian myriapodologist and invertebrate zoologist. He published 138 scientific papers, most of them dealing with his specialist field ...
,
Karl Wilhelm Verhoeff Karl (or Carl) Wilhelm Verhoeff (25 November 1867 – 6 December 1944) was a German myriapodology, myriapodologist and entomology, entomologist, specialising in myriapods (millipedes, centipedes, and related species) as well as woodlouse, woodlice ...
and Ralph Vary Chamberlin, who each described over 1,000 species, as well as
Orator F. Cook Orator Fuller Cook Jr. (May 28, 1867 – April 23, 1949) was an American botanist, entomologist, and agronomist, known for his work on cotton and rubber cultivation and for coining the term "speciation" to describe the process by which new species ...
,
Filippo Silvestri Filippo Silvestri (22 June 1873 – 10 June 1949) was an Italian entomologist. He specialised in world Protura, Thysanura, Diplura and Isoptera, but also worked on Hymenoptera, Myriapoda and Italian Diptera. He is also noted for describing an ...
,
R. I. Pocock Reginald Innes Pocock F.R.S. (4 March 1863 – 9 August 1947) was a British zoologist. Pocock was born in Clifton, Bristol, the fourth son of Rev. Nicholas Pocock and Edith Prichard. He began showing interest in natural history at St. Edward ...
, and Henry W. Brölemann. This was a period when the science of diplopodology flourished: rates of species descriptions were on average the highest in history, sometimes exceeding 300 per year. In 1971, the Dutch biologist
C. A. W. Jeekel Casimir Albrecht Willem Jeekel (1922–2010) was a Dutch people, Dutch myriapodologist and entomologist known for his major contributions to the Taxonomy (biology), taxonomy of millipedes. His 1971 monograph ''Nomenclator Generum et Familiarum Di ...
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. In 1980, the American biologist Richard L. Hoffman published a classification of millipedes which recognized the Penicillata, Pentazonia, and Helminthomorpha, and the first phylogenetic analysis of millipede orders using modern cladistic methods was published in 1984 by Henrik Enghoff of Denmark. A 2003 classification by the American myriapodologist Rowland Shelley is similar to the one originally proposed by Verhoeff, and remains the currently accepted classification scheme (shown below), despite more recent molecular studies proposing conflicting relationships. A 2011 summary of millipede family diversity by William A. Shear placed the order Siphoniulida within the larger group Nematophora.


Fossil record

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. Several living orders also appear in the fossil record. Below are two proposed arrangements of fossil millipede groups. Extinct groups are indicated with a dagger (†). The extinct order
Zosterogrammida Zosterogrammidae is an extinct family of millipedes containing three genera, each with a single species. Fossils are known from the Czech Republic, Scotland, and the USA. Zosterogrammidae constitutes the sole family of the order Zosterogrammida ...
, a chilognath of uncertain position, is not shown.


Relation to other myriapods

Although the relationships of millipede orders are still the subject of debate, the class Diplopoda as a whole is considered a monophyletic group of arthropods: all millipedes are more closely related to each other than to any other arthropods. Diplopoda is a class within the arthropod subphylum Myriapoda, the myriapods, which includes
centipede Centipedes (from New Latin , "hundred", and Latin , " foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', lip, and New Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, an ...
s (class Chilopoda) as well as the lesser-known
pauropods Pauropods are small, pale, millipede-like arthropods. Around 830 species in twelve families are found worldwide, living in soil and leaf mold. They look rather like centipedes, or millipedes, and may be a sister group of the latter. However, this ...
(class Pauropoda) and symphylans (class Symphyla). Within myriapods, the closest relatives or
sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...
of millipedes has long been considered the pauropods, which also have a collum and diplosegments.


Distinction from centipedes

The differences between millipedes and centipedes are a common question from the general public. Both groups of myriapods share similarities, such as long, multi-segmented bodies, many legs, a single pair of antennae, and the presence of postantennal organs, but have many differences and distinct evolutionary histories, as the most recent common ancestor of centipedes and millipedes lived around 450 to 475 million years ago in the Silurian. The head alone exemplifies the differences; millipedes have short, geniculate (elbowed)
antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...
e for probing the substrate, a pair of robust mandibles and a single pair of maxillae fused into a lip; centipedes have long, threadlike antennae, a pair of small mandibles, two pairs of maxillae and a pair of large poison claws.


Characteristics

Millipedes come in a variety of body shapes and sizes, ranging from to around in length, and can have as few as eleven to over three hundred segments. They are generally black or brown in colour, although there are a few brightly coloured species, and some have aposematic colouring to warn that they are toxic. Species of ''
Motyxia ''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 ...
'' produce
cyanide Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms. In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of a ...
as a chemical defence and are
bioluminescent Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some Fungus, fungi, microorganisms including ...
. Body styles vary greatly between major millipede groups. In the
basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...
subclass Penicillata, consisting of the tiny bristle millipedes, the exoskeleton 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 Pentazonia is a taxonomic infraclass of millipedes containing the pill-millipedes (Oniscomorpha) which can roll into a ball and the order Glomeridesmida which cannot. Defining traits (apomorphies) include divided sternites, a labrum with single ...
, containing relatively short-bodied groups such as pill millipedes, and the Helminthomorpha ("worm-like" millipedes), which contains the vast majority of species, with long, many-segmented bodies. They have also lost the gene that codes for the JHAMTl enzyme, which is responsible for catalysing the last step of the production of a juvenile hormone that regulates the development and reproduction in other arthropods like crustaceans, centipedes and insects.


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 In arthropods, the maxillae (singular maxilla) are paired structures present on the head as mouthparts in members of the clade Mandibulata, used for tasting and manipulating food. Embryologically, the maxillae are derived from the 4th and 5th se ...
("jaw lip"). The head contains a single pair of antennae with seven or eight segments and a group of sensory cones at the tip. Many orders also possess a pair of sensory organs known as the Tömösváry organs, shaped as small oval rings posterior and lateral to the base of the antennae. Their function is unknown, but they also occur in some
centipede Centipedes (from New Latin , "hundred", and Latin , " foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', lip, and New Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, an ...
s, and are possibly used to measure humidity or light levels in the surrounding environment. Millipede eyes consist of several simple flat-lensed ocelli arranged in a group or patch on each side of the head. These patches are also called ocular fields or ocellaria. Many species of millipedes, including the entire orders Polydesmida, Siphoniulida, Glomeridesmida,
Siphonophorida Siphonophorida (Greek language, Greek for "tube bearer") is an order of millipedes containing two families and over 100 species. Description Millipedes in the order Siphonophorida are long and worm-like, reaching up to in length and up to 190 ...
and
Platydesmida Platydesmida (Greek for ''platy'' "flat" and ''desmos'' "bond") is an order of millipedes containing two families and over 60 species. Some species practice paternal care, in which males guard the eggs. Description Platydesmidans have a flatte ...
, and cave-dwelling millipedes such as ''
Causeyella ''Causeyella'', is a genus of millipede Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derived from this fe ...
'' and '' Trichopetalum'', had ancestors that could see but have subsequently lost their eyes and are blind.


Body

Millipede bodies may be flattened or cylindrical, and are composed of numerous metameric segments, each with an exoskeleton consisting of four
chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...
ous plates: a single plate above (the tergite), one at each side ( pleurites), and a plate on the underside (
sternite The sternum (pl. "sterna") is the ventral portion of a segment of an arthropod thorax or abdomen. In insects, the sterna are usually single, large sclerites, and external. However, they can sometimes be divided in two or more, in which case the ...
) where the legs attach. In many millipedes, such as Merocheta and Juliformia, these plates are fused to varying degrees, sometimes forming a single cylindrical ring. The plates are typically hard, impregnated with calcium salts. Because they can't close their permanently open spiracles and most species lack a waxy cuticle, millipedes are susceptible to water loss and with a few exceptions must spend most of their time in moist or humid environments. 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" (the three haplosegments are sometimes referred to as a " thorax"). The remaining segments, from the fifth to the posterior, are properly known as diplosegments or double segments, formed by the fusion of two embryonic segments. Each diplosegment bears two pairs of legs, rather than just one as in centipedes. 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 and consists of a legless preanal ring, a pair of anal valves (closeable plates around the anus), and a small scale below the anus. Millipedes in several orders have keel-like extensions of the body-wall known as paranota, which can vary widely in shape, size, and texture; modifications include lobes, papillae, ridges, crests, spines and notches. Paranota may allow millipedes to wedge more securely into crevices, protect the legs, or make the millipede more difficult for predators to swallow. 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 may have a reduced or enlarged first pair of legs. The most conspicuous leg modifications are involved in reproduction, discussed below. Despite the common name, no millipede was known to have 1,000 legs until 2021: common species have between 34 and 400 legs, and the record is held by '' Eumillipes persephone'', with individuals possessing up to 1,306 legs – more than any other creature on Earth.


Internal organs

Millipedes breathe through two pairs of spiracles located ventrally on each segment near the base of the legs. Each opens into an internal pouch, and connects to a system of
tracheae The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from the ...
. The heart runs the entire length of the body, with an aorta stretching into the head. The excretory organs are 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.


Reproduction and growth

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. 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. A few species are parthenogenetic, having few, if any, males. 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; 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. The gonopods develop gradually from walking legs through successive moults until reproductive maturity. 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 small hood-like lids, and are used to store the sperm after copulation. The cyphopod morphology can also be used to identify species. Millipede
sperm Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, whi ...
lack
flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...
, a unique trait among myriapods. In all except the bristle millipedes, copulation occurs with the two individuals facing one another. Copulation may be preceded by male behaviours such as tapping with antennae, running along the back of the female, offering edible glandular secretions, or in the case of some pill-millipedes, stridulation or "chirping". 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. Females lay from ten to three hundred eggs at a time, depending on species, fertilising them with the stored sperm as they do so. Many species 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. In most species, the female abandons the eggs after they are laid, but some species in the orders
Platydesmida Platydesmida (Greek for ''platy'' "flat" and ''desmos'' "bond") is an order of millipedes containing two families and over 60 species. Some species practice paternal care, in which males guard the eggs. Description Platydesmidans have a flatte ...
and
Stemmiulida Stemmiulida is an order of millipedes consisting of approximately 130 species, reaching up to 50 mm in length. It contains a single family, Stemmiulidae. Description Stemmiulids are small to medium sized millipedes, reaching a maximum leng ...
provide parental care for eggs and young. 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, and may also shelter in these during wet weather, and most species eat the discarded exoskeleton after moulting. The adult stage, when individuals become reproductively mature, is generally reached in the final moult stage, which varies between species and orders, although some species continue to moult 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. Millipedes may live from one to ten years, depending on species.


Ecology


Habitat and distribution

Millipedes occur on all continents except Antarctica, and occupy almost all terrestrial habitats, ranging as far north as the
Arctic Circle The Arctic Circle is one of the two polar circles, and the most northerly of the five major circles of latitude as shown on maps of Earth. Its southern equivalent is the Antarctic Circle. The Arctic Circle marks the southernmost latitude at w ...
in Iceland, Norway, and Central Russia, and as far south as Santa Cruz Province, Argentina. Typically forest floor dwellers, they live in leaf litter, dead wood, or soil, with a preference for humid conditions. In
temperate zones In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...
, millipedes are most abundant in moist deciduous forests, and may reach densities of over 1,000 individuals per square metre. Other habitats include coniferous forests, caves, and alpine ecosystems. Deserticolous millipedes, species evolved to live in the desert, like Orthoporus ornatus, may show adaptations like a waxy epicuticle and the ability of water uptake from unsaturated air. Some species can survive freshwater floods and live submerged underwater for up to 11 months. A few species occur near the seashore and can survive in somewhat salty conditions.


Burrowing

The diplosegments of millipedes have evolved in conjunction with their burrowing habits, and nearly all millipedes adopt a mainly subterranean lifestyle. They use three main methods of burrowing; bulldozing, wedging and boring. Members of the orders Julida,
Spirobolida Spirobolida is an order of "round-backed" millipedes containing approximately 500 species in 12 families. Its members are distinguished by the presence of a "pronounced suture that runs "vertically down the front of the head". Most of the spec ...
and
Spirostreptida Spirostreptida is an order (biology), order of long, cylindrical millipedes. There are approximately 1000 described species, making Spirostreptida the third largest order of millipedes after Polydesmida and Chordeumatida. Description Spirostrept ...
, lower their heads and barge their way into the substrate, the collum leading the way. Flat-backed millipedes in the order Polydesmida tend to insert their front end, like a wedge, into a horizontal crevice, and then widen the crack by pushing upwards with their legs, the paranota in this instance constituting the main lifting surface. Boring is used by members of the order
Polyzoniida __NOTOC__ Polyzoniida is an order of millipedes in the Class_(biology)#Hierarchy_of_ranks_below_and_above_the_level_of_class, subterclass Colobognatha containing three families and at least 74 described species. Description Polyzoniidans have a ...
. These have smaller segments at the front and increasingly large ones further back; they propel themselves forward into a crack with their legs, the wedge-shaped body widening the gap as they go. Some millipedes have adopted an above-ground lifestyle and lost the burrowing habit. This may be because they are too small to have enough leverage to burrow, or because they are too large to make the effort worthwhile, or in some cases because they move relatively fast (for a millipede) and are active predators.


Diet

Most millipedes are
detritivore Detritivores (also known as detrivores, detritophages, detritus feeders, or detritus eaters) are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). There are many kinds of invertebrates, ...
s and feed on decomposing vegetation, feces, or organic matter mixed with soil. They often play important roles in the breakdown and decomposition of plant litter: estimates of consumption rates for individual species range from 1 to 11 percent of all leaf litter, depending on species and region, and collectively millipedes may consume nearly all the leaf litter in a region. The leaf litter is fragmented in the millipede gut and excreted as pellets of leaf fragments, algae, fungi, and bacteria, which facilitates decomposition by the microorganisms. Where earthworm populations are low in tropical forests, millipedes play an important role in facilitating microbial decomposition of the leaf litter. Some millipedes are herbivorous, feeding on living plants, and some species can become serious pests of crops. Millipedes in the order Polyxenida graze algae from bark, and
Platydesmida Platydesmida (Greek for ''platy'' "flat" and ''desmos'' "bond") is an order of millipedes containing two families and over 60 species. Some species practice paternal care, in which males guard the eggs. Description Platydesmidans have a flatte ...
feed on fungi. A few species are omnivorous or in Callipodida and Chordeumatida occasionally carnivorous, feeding on insects, centipedes, earthworms, or snails. Some species have piercing mouth parts that allow them to suck up plant juices.


Predators and parasites

Millipedes are preyed on by a wide range of animals, including various
reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...
s,
amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...
s, birds,
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s, and insects. Mammalian predators such as coatis and
meerkat MeerKAT, originally the Karoo Array Telescope, is a radio telescope consisting of 64 antennas in the Meerkat National Park, in the Northern Cape of South Africa. In 2003, South Africa submitted an expression of interest to host the Square Kilom ...
s roll captured millipedes on the ground to deplete and rub off their defensive secretions before consuming their prey, and certain
poison dart frog Poison dart frog (also known as dart-poison frog, poison frog or formerly known as poison arrow frog) is the common name of a group of frogs in the family Dendrobatidae which are native to tropical Central and South America. These species are ...
s are believed to incorporate the toxic compounds of millipedes into their own defences. Several invertebrates have specialised behaviours or structures to feed on millipedes, including larval glowworm beetles, '' Probolomyrmex'' ants, chlamydephorid slugs, and predaceous dung beetles of the genera ''
Sceliages ''Sceliages'', Westwood, ('σκέλος' = leg), is a sub-genus of the ''Scarabaeus'' dung beetles, and are obligate predators of spirostreptid, spirobolid and julid millipedes, having renounced the coprophagy for which they were named. The ...
'' and ''
Deltochilum ''Deltochilum'' is a genus of dung beetles in the family Scarabaeidae. There are at least 100 described species in ''Deltochilum''. See also * List of Deltochilum species References External links

* * Scarabaeidae genera Deltochil ...
''. A large subfamily of
assassin bugs The Reduviidae are a large cosmopolitan family of the order Hemiptera (true bugs). Among the Hemiptera and together with the Nabidae almost all species are terrestrial ambush predators: most other predatory Hemiptera are aquatic. The main example ...
, the
Ectrichodiinae The Ectrichodiinae are a subfamily of assassin bugs (Reduviidae) known for specializing on millipedes as prey. The group comprises more than 600 species in about 115 genera, making it a fairly large subfamily. The bugs are also known for their ...
with over 600 species, has specialised in preying upon millipedes. Parasites of millipedes include
nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...
s, phaeomyiid flies, and acanthocephalans. Nearly 30 fungal species of the order
Laboulbeniales The Laboulbeniales is an order of Fungi within the class Laboulbeniomycetes. They are also known by the colloquial name beetle hangers or labouls. The order includes around 2,325 species of obligate insect ectoparasites that produce cellular ...
have been found growing externally on millipedes, but some species may be commensal rather than parasitic.


Defence mechanisms

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 "repugnatorial glands"), along the sides of their bodies as a secondary defence. Among the many irritant and toxic chemicals found in these secretions are alkaloids, benzoquinones, phenols, terpenoids, and
hydrogen cyanide Hydrogen cyanide, sometimes called prussic acid, is a chemical compound with the formula HCN and structure . It is a colorless, extremely poisonous, and flammable liquid that boils slightly above room temperature, at . HCN is produced on an ...
. Some of these substances are
caustic Caustic most commonly refers to: * Causticity, a property of various corrosive substances ** Sodium hydroxide, sometimes called ''caustic soda'' ** Potassium hydroxide, sometimes called ''caustic potash'' ** Calcium oxide, sometimes called ''caus ...
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. Some of these defensive compounds also show antifungal activity. 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.


Other inter-species interactions

Some millipedes form mutualistic relationships with organisms of other species, in which both species benefit from the interaction, or 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 Myrmecophily ( , ) is the term applied to positive interspecies associations between ants and a variety of other organisms, such as plants, other arthropods, and fungi. Myrmecophily refers to mutualistic associations with ants, though in its m ...
, especially within the family
Pyrgodesmidae Pyrgodesmidae is a family of flat-backed millipedes in the order Polydesmida. The family contains over 200 species distributed in tropics around the world. Some species are found only in ant colonies An ant colony is a population of a si ...
(Polydesmida), which contains "obligate myrmecophiles", species which have only been found in ant colonies. More species are "facultative myrmecophiles", non-exclusively associated with ants, including many species of Polyxenida that have been found in ant nests around the world. Many millipede species have commensal relationships with mites of the orders Mesostigmata and
Astigmata Astigmatina is a clade of mites in the superorder Acariformes. Astigmata has been ranked as an order or suborder in the past, but was lowered to the unranked clade Astigmatina of the clade Desmonomatides (synonym Desmonomata) in the order Sarcopt ...
. Many of these mites are believed to be
phoretic Phoresis or phoresy is a non-permanent, commensalistic interaction in which one organism (a phoront or phoretic) attaches itself to another (the host) solely for the purpose of travel. Phoresis has been observed directly in ticks and mites s ...
rather than parasitic, which means that they use the millipede host as a means of dispersal. 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.


Interactions with humans

Millipedes generally have little impact on human economic or social well-being, especially in comparison with insects, although locally they can be a nuisance or agricultural
pest Pest or The Pest may refer to: Science and medicine * Pest (organism), an animal or plant deemed to be detrimental to humans or human concerns ** Weed, a plant considered undesirable * Infectious disease, an illness resulting from an infection ** ...
. Millipedes do not bite, and their defensive secretions are mostly harmless to humans — usually causing only minor discolouration on the skin — but the secretions of some tropical species may cause pain, itching, local erythema,
edema Edema, also spelled oedema, and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's Tissue (biology), tissue. Most commonly, the legs or arms are affected. Symptoms may include skin which feels t ...
,
blister A blister is a small pocket of body fluid (lymph, serum, plasma, blood, or pus) within the upper layers of the skin, usually caused by forceful rubbing (friction), burning, freezing, chemical exposure or infection. Most blisters are filled wi ...
s, eczema, and occasionally cracked skin. Eye exposures to these secretions causes general irritation and potentially more severe effects such as conjunctivitis and keratitis. This is called millipede burn. First aid consists of flushing the area thoroughly with water; further treatment is aimed at relieving the local effects. Some millipedes are considered household pests, including ''
Xenobolus carnifex ''Xenobolus carnifex'' is a species of spirobolidan millipede found in South India and Sri Lanka. It is a common species and can become a household pest, infesting and damaging thatched roofs Thatching is the craft of building a roof with ...
'' which can infest thatched roofs in India, and '' Ommatoiulus moreleti'', which periodically invades homes in Australia. Other species exhibit periodical
swarming behaviour Swarm behaviour, or swarming, is a collective behaviour exhibited by entities, particularly animals, of similar size which aggregate together, perhaps milling about the same spot or perhaps moving ''en masse'' or migrating in some direction. ...
, which can result in home invasions, crop damage, and train delays when the tracks become slippery with the crushed remains of hundreds of millipedes. Some millipedes can cause significant damage to crops: the
spotted snake millipede ''Blaniulus guttulatus'', commonly known as the spotted snake millipede is a species of millipede in the family Blaniulidae that can be found in Central and Western Europe (except for Portugal). It has been introduced in North American countries ...
(''Blaniulus guttulatus'') is a noted pest of
sugar beet A sugar beet is a plant whose root contains a high concentration of sucrose and which is grown commercially for sugar production. In plant breeding, it is known as the Altissima cultivar group of the common beet (''Beta vulgaris''). Together wi ...
s and other root crops, and as a result is one of the few millipedes with a
common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...
. Some of the larger millipedes in the orders Spirobolida, Spirostreptida, and
Sphaerotheriida Sphaerotheriida is an order of millipedes in the infraclass Pentazonia, sometimes known as giant pill millipedes. They inhabit Southern Africa, Madagascar, South and Southeast Asia, Australia and New Zealand. Like the Northern Hemisphere pill m ...
are popular as pets. Some species commonly sold or kept include species of ''
Archispirostreptus ''Archispirostreptus'' is a genus of giant African millipedes in family Spirostreptidae, containing 26 species: * '' Archispirostreptus arabs'' Pocock, 1876 * '' Archispirostreptus beccarii'' Silvestri, 1895 * '' Archispirostreptus boettegi'' S ...
'', '' Aphistogoniulus'', ''
Narceus ''Narceus'' is a genus of large cylindrical millipedes of the family Spirobolidae native to eastern North America. The genus comprises three or four species, two of which are endemic to Florida, and the remainder forming a species complex. The ...
'', and ''
Orthoporus ''Orthoporus'' is a genus of spirostreptid millipedes, containing around 80 species, distributed from the southern United States to Brazil and Argentina. * '' Orthoporus absconsus'' Chamberlin, 1922 * '' Orthoporus acanthethus'' Chamberlin, 194 ...
''. Millipedes appear in folklore and traditional medicine around the world. Some cultures associate millipede activity with coming rains. In Zambia, smashed millipede pulp is used to treat wounds, and the Bafia people of Cameroon use millipede juice to treat earache. In certain Himalayan Bhotiya tribes, dry millipede smoke is used to treat haemorrhoids. Native people in Malaysia use millipede secretions in poison-tipped arrows. The secretions of ''Spirobolus bungii'' have been observed to inhibit division of human cancer cells. The only recorded usage of millipedes as food by humans comes from the
Bobo people The Bobo are a Mande ethnic group living primarily in Burkina Faso, with some living north in Mali. Bobo is also a shortened name of the second-largest city in Burkina Faso, Bobo-Dioulasso. Background In much of the literature on African art, ...
of Burkina Faso in West Africa, who consume boiled, dried millipedes belonging to the families
Gomphodesmidae Gomphodesmidae is a family of millipedes in the order Polydesmida, containing around 55 genera and 150 species. The family is native to Africa, and occurs primarily in savanna habitat (open-canopy grasslands) from South Africa north to Senegal ...
and
Spirostreptidae Spirostreptidae is a family of millipedes in the order Spirostreptida. It contains around 100 genera distributed in North and South America, the eastern Mediterranean, continental Africa, Madagascar, and Seychelles. It contains the following gene ...
to which they add tomato sauce. Millipedes have also inspired and played roles in scientific research. In 1963, a walking vehicle with 36 legs was designed, said to have been inspired by a study of millipede locomotion. Experimental robots have had the same inspiration, in particular when heavy loads are needed to be carried in tight areas involving turns and curves. In biology, some authors have advocated millipedes as
model organism A model organism (often shortened to model) is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workin ...
s for the study of arthropod physiology and the developmental processes controlling the number and shape of body segments. Similar to vermicompost, millipedes can be used to convert plant matter into compost in what has been named millicomposting, which improves the quality of the compost.Millicompost: an alternate biocompost for forest nurseries
/ref>


References


External links


Milli-PEET: The Class Diplopoda
– The Field Museum, Chicago


Diplopoda: Guide to New Zealand Soil Invertebrates
– Massey University


British Myriapod & Isopod Group
{{DEFAULTSORT:Millipede Detritivores Wenlock first appearances Extant Silurian first appearances Myriapods Taxa named by Henri Marie Ducrotay de Blainville