Millipede

Millipede

Overview
Millipedes are arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

s that have two pairs of legs
Arthropod leg
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...

 per segment (except for the first segment behind the head which does not have any appendage
Appendage
In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...

s at all, and the next few which only have one pair of legs). Each segment that has two pairs of legs is a result of two single segments fused together as one. Most millipedes have very elongated cylindrical bodies, although some are flattened dorso-ventrally, while pill millipede
Pill millipede
Pill millipedes make up two orders of millipedes, often grouped together into a single superorder, Oniscomorpha. The name Oniscomorpha refers to the resemblance of pill millipedes to certain woodlice, namely the pillbugs of the family Armadillidiidae, also called "potato bugs", "doodlebugs", or...

s are shorter and can roll into a ball, like a pillbug
Armadillidiidae
Armadillidiidae is a family of woodlice, a terrestrial crustacean group in the order Isopoda. Unlike members of other woodlouse families, members of this family can roll into a ball, an ability they share with the outwardly similar but unrelated pill millipedes and other animals...

.

The name "millipede" is a compound word formed from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 roots ("thousand") and ("foot").
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Encyclopedia
Millipedes are arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

s that have two pairs of legs
Arthropod leg
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...

 per segment (except for the first segment behind the head which does not have any appendage
Appendage
In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...

s at all, and the next few which only have one pair of legs). Each segment that has two pairs of legs is a result of two single segments fused together as one. Most millipedes have very elongated cylindrical bodies, although some are flattened dorso-ventrally, while pill millipede
Pill millipede
Pill millipedes make up two orders of millipedes, often grouped together into a single superorder, Oniscomorpha. The name Oniscomorpha refers to the resemblance of pill millipedes to certain woodlice, namely the pillbugs of the family Armadillidiidae, also called "potato bugs", "doodlebugs", or...

s are shorter and can roll into a ball, like a pillbug
Armadillidiidae
Armadillidiidae is a family of woodlice, a terrestrial crustacean group in the order Isopoda. Unlike members of other woodlouse families, members of this family can roll into a ball, an ability they share with the outwardly similar but unrelated pill millipedes and other animals...

.

The name "millipede" is a compound word formed from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 roots ("thousand") and ("foot"). Despite their name, millipedes do not have 1,000 legs, although the rare species Illacme plenipes
Illacme plenipes
Illacme plenipes is a millipede found in the central region of the U.S. state of California. It has 750 legs, more than any other millipede. It was first seen in 1926, but was not rediscovered until 2005.-Legs:...

has up to 750. Common species have between 36 and 400 legs. The class contains around 10,000 species in 13 orders and 115 families. The giant African millipede (Archispirostreptus gigas
Archispirostreptus gigas
Archispirostreptus gigas, the giant African millipede, is one of the largest millipedes, growing up to in length, in circumference, and has 256 legs....

), known as shongololos, is the largest species of millipede.

Millipedes are detritivore
Detritivore
Detritivores, also known as detritophages or detritus feeders or detritus eaters or saprophages, are heterotrophs that obtain nutrients by consuming detritus . By doing so, they contribute to decomposition and the nutrient cycles...

s and slow moving. Most millipedes eat decaying leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 and other dead plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

 matter, moisturising the food with secretions and then scraping it in with their jaws. However, they can also be minor garden pests, especially in greenhouse
Greenhouse
A greenhouse is a building in which plants are grown. These structures range in size from small sheds to very large buildings...

s where they can cause severe damage to emergent seedlings. Signs of millipede damage include the stripping of the outer layers of a young plant stem and irregular damage to leaves and plant apices, the very top of a plant.

Millipedes can be easily distinguished from the somewhat similar and related centipede
Centipede
Centipedes are arthropods belonging to the class Chilopoda of the subphylum Myriapoda. They are elongated metameric animals with one pair of legs per body segment. Despite the name, centipedes can have a varying number of legs from under 20 to over 300. Centipedes have an odd number of pairs of...

s (Class Chilopoda), which move rapidly, and have a single pair of legs for each body segment.

Evolution


This class of arthropod is thought to be among the first animals to have colonised land during the Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...

 geologic period. These early forms probably ate moss
Moss
Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...

es and primitive vascular plant
Vascular plant
Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the clubmosses, Equisetum, ferns, gymnosperms and angiosperms...

s. The oldest known land creature, Pneumodesmus newmani
Pneumodesmus newmani
Pneumodesmus newmani is a species of millipede that lived , in the Late Silurian. It is the first myriapod, and the oldest known creature to have lived on land. It was discovered in 2004, and is known from a single specimen from Stonehaven, Aberdeenshire, Scotland.-Discovery:The single,...

, was a 1 centimetre (0.393700787401575 in) long millipede, and lived 428 million years ago. In the Upper Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...

 , Arthropleura
Arthropleura
Arthropleura was a 0.3–2.6 metre long relative of centipedes and millipedes, native to the Upper Carboniferous of what is now northeastern North America and Scotland...

became the largest known land invertebrate of all time, reaching lengths of up to 2.6 metres (8.5 ft).

Characteristics


Millipedes range from 2 to 280 mm (0.078740157480315 to 11 in) in length, and can have as few as eleven, to over a hundred segments. They are generally black or brown in colour, although there are a few brightly coloured species.

The millipede's most obvious feature is its large number of legs. Having very many short legs makes millipedes rather slow, but they are powerful burrowers. With their legs and body length moving in a wavelike pattern, they easily force their way underground head first. They also seem to have some engineering ability, reinforcing the tunnel by rearranging the particles around it. Their bodies have segmented sections which makes them move in a wave-like form.

The head of a millipede is typically rounded above and flattened below and bears large mandible
Mandible (arthropod)
thumb|250px|The mandibles of a [[Bull ant]]The mandible of an arthropod is either of a pair of mouthparts used for biting, cutting and holding food. Mandibles are often simply referred to as jaws. Mandibles are present in the extant subphyla Myriapoda , Crustacea and Hexapoda...

s. The body is flattened or cylindrical, with a single chitinous plate
Tergum
A tergum is the dorsal portion of an arthropod segment other than the head. The anterior edge is called the base and posterior edge is called the apex or margin. A given tergum may be divided into hardened plates or sclerites commonly referred to as tergites...

 above, one at each side, and two or three on the underside. 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. Because they lack a waxy cuticle millipedes are susceptible to water loss, and must spend most of their time in moist or humid environments.

Unlike centipede
Centipede
Centipedes are arthropods belonging to the class Chilopoda of the subphylum Myriapoda. They are elongated metameric animals with one pair of legs per body segment. Despite the name, centipedes can have a varying number of legs from under 20 to over 300. Centipedes have an odd number of pairs of...

s and other similar animals, each segment bears two pairs of legs, rather than just one. This is because each is actually formed by the fusion of two embryonic segments, and is therefore properly referred to as a "diplosegment", or double segment. The first few segments behind the head are not fused in this fashion, and the first segment is legless, called a collum segment while the second to fourth have one pair each. In some millipedes, the last few segments may also be legless. The final segment bears a telson
Telson
The telson is the last division of the body of a crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca is often present. Together with the...

.

Millipedes breathe through two pairs of spiracle
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...

s on each diplosegment. Each opens into an internal pouch, and connects to a system of tracheae
Invertebrate trachea
The invertebrate trachea refers to the open respiratory system composed of spiracles, tracheae, and tracheoles that terrestrial arthropods have to transport metabolic gases to and from tissues....

. The heart runs the entire length of the body, with an aorta
Aorta
The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries...

 stretching into the head. The excretory organs are two pairs of malpighian tubules, located near the mid-part of the gut.

The head contains a pair of sensory organs known as the Tömösváry organs. These are found just posterior and lateral to the antennae, and are shaped as small and oval rings at the base of the antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....

. They are probably used to measure the humidity in the surroundings, and they may have some chemoreceptory abilities too. Millipede eyes consist of a number of simple flat lensed ocelli arranged in a group on the front/side of the head. Many species of millipedes, including cave-dwelling millipedes such as Causeyella
Causeyella
Causeyella, is a genus of millipedes comprising three species:*Causeyella causeyae Shear, 2003*Causeyella dendropus *Causeyella youngsteadtorum Shear, 2003...

, have secondarily lost their eyes.

According to Guinness World Records
Guinness World Records
Guinness World Records, known until 2000 as The Guinness Book of Records , is a reference book published annually, containing a collection of world records, both human achievements and the extremes of the natural world...

 the African giant black millipede Archispirostreptus gigas
Archispirostreptus gigas
Archispirostreptus gigas, the giant African millipede, is one of the largest millipedes, growing up to in length, in circumference, and has 256 legs....

can grow to 38.6 centimetres (15.2 in).

Diet


Most millipedes are herbivorous, and feed on decomposing vegetation or organic matter mixed with soil. A few species are omnivorous or carnivorous, and may prey on small arthropods, such as insects and centipedes, or on earthworm
Earthworm
Earthworm is the common name for the largest members of Oligochaeta in the phylum Annelida. In classical systems they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, even though the internal male segments are anterior to the female...

s. Some species have piercing mouth parts that allow them to feed on plant juices.

The digestive tract is a simple tube with two pairs of salivary gland
Salivary gland
The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...

s to help digest the food. Many millipedes moisten their food with saliva before eating it.

Reproduction



Male millipedes can be differentiated from female millipedes by the presence of one or two pairs of legs modified into gonopods. These modified legs, which are usually on the seventh segment, are used to transfer sperm packets to the female during copulation. A few species are parthenogenetic
Parthenogenesis
Parthenogenesis is a form of asexual reproduction found in females, where growth and development of embryos occur without fertilization by a male...

, having few, if any, males.

The genital openings are located on the third segment, and are accompanied in the male by one or two penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...

es, which deposit the sperm packets onto the gonopods. In the female, the genital pores open into a small chamber, or vulva
Vulva
The vulva consists of the external genital organs of the female mammal. This article deals with the vulva of the human being, although the structures are similar for other mammals....

, which is covered by a small hood-like cover, and is used to store the sperm after copulation.

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.

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
Ecdysis
Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...

, adding further segments and legs as they do so. Some species moult within specially prepared chambers, which they may also use to wait out dry weather, and most species eat the shed exoskeleton after moulting. Millipedes live from one to ten years, depending on species.

Defense mechanisms



Due to their lack of speed and their inability to bite or sting, millipedes' primary defense mechanism is to curl into a tight coil — protecting their delicate legs inside an armored body exterior
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...

. Many species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 also emit poison
Poison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....

ous liquid secretions or hydrogen cyanide gas through microscopic pores called odoriferous glands along the sides of their bodies as a secondary defense. Some of these substances are caustic and can burn
Millipede burn
Millipede burns are a cutaneous condition caused by some millipedes that secrete a toxic liquid that causes a brownish pigmentation or burn when it comes into contact with the skin. Some millipedes produce quinones in their defensive secretions, which have been reported to cause brown staining of...

 the exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...

 of ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...

s and other insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

 predators, and the skin and eyes of larger predators. Animals such as Capuchin monkey
Capuchin monkey
The capuchins are New World monkeys of the genus Cebus. The range of capuchin monkeys includes Central America and South America as far south as northern Argentina...

s have been observed intentionally irritating millipedes in order to rub the chemicals on themselves to repel mosquito
Mosquito
Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...

es. At least one species, Polyxenus fasciculatus
Polyxenus fasciculatus
Polyxenus fasciculatus is a species of millipede about long which is notable for its use of detachable bristles which entangle predatory ants. The bristles have grappling hooks at the tip which lock on to the setae of an ant, and barbs along their length which cause them to interlink ....

, employs detachable bristle
Bristle
A bristle is a stiff hair or feather. Also used are synthetic materials such as nylon in items such as brooms and sweepers. Bristles are often used to make brushes for cleaning uses, as they are strongly abrasive; common examples include the toothbrush and toilet brush...

s to entangle ants.

As far as human
Human
Humans are the only living species in the Homo genus...

s are concerned, this chemical brew is fairly harmless, usually causing only minor effects on the skin, the main effect being discoloration, but other effects may also include pain, itching, local erythema
Erythema
Erythema is redness of the skin, caused by hyperemia of the capillaries in the lower layers of the skin. It occurs with any skin injury, infection, or inflammation...

, edema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...

, blister
Blister
A blister is a small pocket of fluid within the upper layers of the skin, typically caused by forceful rubbing , burning, freezing, chemical exposure or infection. Most blisters are filled with a clear fluid called serum or plasma...

s, eczema
Eczema
Eczema is a form of dermatitis, or inflammation of the epidermis . In England, an estimated 5.7 million or about one in every nine people have been diagnosed with the disease by a clinician at some point in their lives.The term eczema is broadly applied to a range of persistent skin conditions...

, and occasionally cracked skin. Eye exposures to these secretions causes general eye irritation and potentially more severe effects such as conjunctivitis
Conjunctivitis
Conjunctivitis refers to inflammation of the conjunctiva...

 and keratitis
Keratitis
Keratitis is a condition in which the eye's cornea, the front part of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves impaired eyesight.-Types:...

. First aid
First aid
First aid is the provision of initial care for an illness or injury. It is usually performed by non-expert, but trained personnel to a sick or injured person until definitive medical treatment can be accessed. Certain self-limiting illnesses or minor injuries may not require further medical care...

 consists of flushing the area thoroughly with water; further treatment is aimed at relieving the local effects.

Classification


The living members of the Diplopoda are divided into fifteen orders in three subclasses. The basal subclass Penicillata contains 160 species whose exoskeleton is not calcified, and which are covered in seta
Seta
Seta is a biological term derived from the Latin word for "bristle". It refers to a number of different bristle- or hair-like structures on living organisms.-Animal setae:In zoology, most "setae" occur in invertebrates....

e or bristles. All other milipedes belong to the Chilognatha in the strict sense.

The subclass Pentazonia contains the short-bodied pill millipede
Pill millipede
Pill millipedes make up two orders of millipedes, often grouped together into a single superorder, Oniscomorpha. The name Oniscomorpha refers to the resemblance of pill millipedes to certain woodlice, namely the pillbugs of the family Armadillidiidae, also called "potato bugs", "doodlebugs", or...

s, which are capable of rolling themselves into a ball ("volvation"). The subclass Helminthomorpha contains the great majority of the species.

The subgroups of millipedes in phylogenetic sequence, from most basal to most advanced, are:


  • Basal genus Eileticus (fossil)
  • Subclass Penicillata Latreille, 1831
    • Order Polyxenida Lucas, 1840
  • Subclass Arthropleuridea
    Arthropleuridea
    Arthropleuridea was a subclass of myriapod arthropods that flourished during the Carboniferous period, having first arose during the Silurian, and perishing due to climate change during the Early Permian. Members are defined by diplosomy, paranotal tergal lobes separated from the axis by a suture,...

     (tentatively placed here; fossil
    Fossil
    Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

    )
  • Subclass Zosterogrammida Wilson, 2005 (fossil)
  • Subclass Pentazonia Brandt, 1833
    • Basal genus Amynilyspes (fossil)
    • Superorder Limacomorpha
      • Order Glomeridesmida Latzel, 1884
    • Superorder Oniscomorpha
      • Order Glomerida Leach, 1814
      • Order Sphaerotheriida
        Sphaerotheriida
        Sphaerotheriida is an order of millipedes in the subclass Pentazonia, sometimes known as giant pill millipedes. They inhabit the Southern Hemisphere. Like the Northern Hemisphere pill millipedes of the order Glomerida, these millipedes can roll into a ball when disturbed...

         Brandt, 1833
        • Family Sphaerotheriidae
          Sphaerotheriidae
          Sphaerotheriidae is a family of giant pill millipedes of the class Diplopoda. Millipedes of this family are distributed in South Africa. -Selected genera:...

           Koch, 1847
        • Family Sphaeropoeidae Brölemann, 1913
  • Subclass Archipolypoda Scudder, 1882
  • Subclass Helminthomorpha Pocock, 1887
    • Superorder Pleurojulida Schneider & Werneburg, 1998 (fossil)
    • Superorder Colobognatha (paraphyletic?)
      • Order Polyzoniida Gervais, 1844
      • Order Platydesmida DeSaussure, 1860
      • Order Siphonocryptida (formerly in Polyzoniida)
      • Order Siphonophorida Hoffman, 1980
    • Superorder "Merocheta"
      • Order Polydesmida
        Polydesmida
        Polydesmida is the largest order of millipedes, with more than 2,700 species in more than 170 genera, including all the millipedes reported to produce hydrogen cyanide .-Description:...

         Pocock, 1887
    • Superorder Nematophora
      • Basal genus Hexecontasoma (fossil)
      • Order Callipodida Bollman, 1893
      • Order Chordeumatida Koch, 1847
      • Order Stemmiulida Pocock, 1894
    • Superorder Diplocheta
      Diplocheta
      The name Diplocheta has been variously used for various taxa:* A superorder of millipedes The name Diplocheta has been variously used for various taxa:* A superorder of millipedes The name Diplocheta has been variously used for various taxa:* A superorder of millipedes (class Diplopoda (Cook,...

      • Order "Xyloiuloida" Cook, 1895 (fossil)
      • Order Julida Brandt, 1833
      • Order Siphoniulida Cook, 1895
      • Order Spirobolida
        Spirobolida
        Spirobolida is an order of "round-backed" millipedes. Its members are distinguished by the presence of a "pronounced suture that runs "vertically down the front of the head"...

      • Order Spirostreptida
        Spirostreptida
        Spirostreptida is an order of millipedes, comprising the following families:*Atopogestidae*Cambalidae*Cambalopsidae*Choctellidae*Epinannolenidae*Glyphiulidae*Harpagophoridae*Iulomorphidae*Odontopygidae*Pericambalidae*Pseudonannolenidae...


External links