Pauropoda

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Pauropoda
Temporal range: 40–0  Ma
Eurypauropodid (12742282145) crop.jpg
A eurypauropod from New Zealand
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Myriapoda
Class: Pauropoda
Orders
Synonyms [1]
  • Heterognathes de Saussure & Humbert, 1872
  • Heterognatha Tömösváry, 1883
  • Monopoda Bollman, 1893

Pauropods are small, pale, millipede-like arthropods. Around 830 species in twelve families [2] are found worldwide, living in soil and leaf mould. They look rather like centipedes, but are probably the sister group to millipedes. [3]

Contents

Anatomy and ecology

Ventral and dorsal views of Pauropus amicus from New South Wales, Australia. Pauropus amicus.jpg
Ventral and dorsal views of Pauropus amicus from New South Wales, Australia.

Pauropods are soft, cylindrical animals with bodies 0.5 to 2 millimetres (0.02 to 0.08 in) long. [3] The first instar has three pairs of legs, but that number increases with each moult so that adult species may have nine to eleven pairs of legs. They have neither eyes nor hearts, although they do have sensory organs which can detect light. The body segments have ventral tracheal/spiracular pouches forming apodemes similar to those in millipedes and Symphyla, although the trachea usually connected to these structures are absent in most species. There are long sensory hairs located throughout the body segments. Pauropods can usually be identified because of their distinctive anal plate, which is unique to pauropods. Different species of pauropods can be identified based on the size and shape of their anal plate. The antennae are branching, biramous, and segmented, which is distinctive for the group. [4] Pauropods are usually either white or brown. [5]

Pauropods live in the soil, usually at densities of less than 100 per square metre (9/sq ft). [4]

Evolution and systematics

Though no fossil pauropods have been found from before the time of the Baltic amber ( 40 to 35 million years ago ), they seem to be an old group closely related to the millipedes (Diplopoda). Their head capsules show great similarities to millipedes: both have three pairs of mouthparts and the genital openings occur in the anterior part of the body. Moreover, both groups have a pupoid phase at the end of the embryonic development. The two groups probably have a common origin.

There are two orders: Hexamerocerata and Tetramerocerata; Hexamerocerata has a purely tropical range, while in Tetramerocerata most genera are subcosmopolitan. [6] Hexamerocerata has a 6-segmented and strongly telescopic antennal stalk and a 12-segmented trunk with 12 tergites and 11 pairs of legs. The representatives are white and proportionately long and large. The one family in this order, Millotauropodidae, has one genus and a few species. [6] Tetramerocerata has a 4-segmented and scarcely telescopic antennal stalk, 6 tergites, and 8–10 pairs of legs. Representatives of this order are often small (sometimes very small), and white or brownish. Most species have nine pairs of legs as adults. [6] The four families include Pauropodidae, Afrauropodidae, Brachypauropodidae, and Eurypauropodidae. Most genera and species belong to the family Pauropodidae.

Behavior, reproduction, and diet

Pauropods are shy of light, and will attempt to distance themselves from light sources. [7] Pauropods occasionally migrate upwards or downwards throughout the soil based on moisture levels. Male pauropods place small packets of sperm on the ground, which the females use to impregnate themselves with. Pauropods have been known to eat mold, fungal hyphae, and the root hairs of plants. [5]

Related Research Articles

Millipede Class of arthropods

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 being 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 ball. Although the name "millipede" derives from the Latin for "thousand feet", no known species has 1,000; the record of 750 legs belongs to Illacme plenipes. There are approximately 12,000 named species classified into 16 orders and around 140 families, making Diplopoda the largest class of myriapods, an arthropod group which also includes centipedes and other multi-legged creatures.

Centipede Many-legged arthropods with elongated bodies

Centipedes are predatory arthropods belonging to the class Chilopoda of the subphylum Myriapoda, an arthropod group which also includes millipedes and other multi-legged creatures. Centipedes are elongated metameric creatures with one pair of legs per body segment. Most centipedes are generally venomous and can inflict painful bites, injecting their venom through pincer-like appendages known as forcipules. Despite the name, centipedes can have a varying number of legs, ranging from 30 to 354. Centipedes always have an odd number of pairs of legs. Therefore, no centipede has exactly 100 legs. Like spiders and scorpions, centipedes are predominantly carnivorous.

Antenna (biology)

Antennae, sometimes referred to as "feelers", are paired appendages used for sensing in arthropods.

Symphyla

Symphylans, also known as garden centipedes or pseudocentipedes, are soil-dwelling arthropods of the class Symphyla in the subphylum Myriapoda. Symphylans resemble centipedes, but are very small, non-venomous, and only distantly related to both centipedes and millipedes. They can move rapidly through the pores between soil particles, and are typically found from the surface down to a depth of about 50 centimetres (20 in). They consume decaying vegetation, but can do considerable harm in an agricultural setting by consuming seeds, roots, and root hairs in cultivated soil.

Myriapoda Subphylum of arthropods

Myriapoda (Ancient Greek myria- + pous is a subphylum of arthropods containing millipedes, centipedes, and others. The group contains over 16,000 species, most of which are terrestrial. Although their name suggests they have myriad legs, myriapods range from having up to 750 legs to having fewer than ten legs.

Cercus

Cerci are paired appendages on the rear-most segments of many arthropods, including insects and symphylans. Many forms of cerci serve as sensory organs, but some serve as pinching weapons or as organs of copulation. In many insects, they simply may be functionless vestigial structures.

Gonopore Invertebrate genital pore

A gonopore, sometimes called a gonadopore, is a genital pore in many invertebrates. Hexapods, including insects have a single common gonopore, except mayflies, which have a pair of gonopores. More specifically, in the unmodified female it is the opening of the common oviduct, and in the male, it is the opening of the ejaculatory duct.

Pill millipede Order of millipedes

Pill millipedes are any members of two living orders of millipedes, often grouped together into a single superorder, Oniscomorpha. The name Oniscomorpha refers to the millipedes' resemblance to certain woodlice (Oniscidea), also called pillbugs or "roly-polies". However, millipedes and woodlice are not closely related ; rather, this is a case of convergent evolution.

Arthropod mouthparts

The mouthparts of arthropods have evolved into a number of forms, each adapted to a different style or mode of feeding. Most mouthparts represent modified, paired appendages, which in ancestral forms would have appeared more like legs than mouthparts. In general, arthropods have mouthparts for cutting, chewing, piercing, sucking, shredding, siphoning, and filtering. This article outlines the basic elements of four arthropod groups: insects, myriapods, crustaceans and chelicerates. Insects are used as the model, with the novel mouthparts of the other groups introduced in turn. Insects are not, however, the ancestral form of the other arthropods discussed here.

Glomerida Order of millipedes

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 have enlarged rear legs involved in mating. The order includes about 30 genera and at least 280 species, including Glomeris marginata, the common European pill-millipede. The order contains members in Europe, South-east Asia and the Americas from California to Guatemala. Although historically considered closely related with the similar sphaerotheriidans that also enroll, some DNA evidence suggest they may be more closely related to glomeridesmidans, a poorly known order that does not enroll.

Polyxenida Order of millipedes

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

Siphonophorida Order of millipedes

Siphonophorida is an order of millipedes containing two families and over 100 species. This order includes the millipede with the most legs, Illacme plenipes.

Callipodida Order of myriapods

Callipodida is an order of millipedes containing around 130 species, many characterized by crests or ridges.

Colobognatha Clade of millipedes

Colobognatha is a clade of helminthomorph millipedes containing four orders: Platydesmida, Polyzoniida, Siphonocryptida, and Siphonophorida.

Juliformia Suborder of millipedes

Juliformia is a taxonomic superorder of millipedes containing three living orders: Julida, Spirobolida, and Spirostreptida, and the extinct group Xyloiuloidea known only from fossils. The species possess long cylindrical bodies with sclerites fused into complete rings. Juliform millipedes possess defensive repugnatorial glands on all body segments except the last few, and are the only known millipedes to produce quinones in their defensive secretions. Juliform males have two pairs of gonopods consisting of the modified 8th and 9th pair of legs: in Julida and Spirobolida the posterior gonopods are primarily involved in sperm-transferring, while in Spirostreptida it is the anterior gonopods. Juliformians also lack Tömösváry organs and have a large collum which overhangs the rear of the head.

Bollmania is a genus of millipedes with around six species occurring from Central through East Asia, including Iran, Pakistan, Tajikistan, and China. The genus was established by entomologist Filippo Silvestri in 1896, and is named in honor of Charles Harvey Bollman. Bollmania is the sole genus of the family Caspiopetalidae.

Millotauropus is a genus of pauropods, comprising the monotypic family Millotauropodidae in the monotypic order Hexamerocerata. Eight species are known. Species of Hexamerocerata are characterized by a 12-segmented body, a 6-segmented antenna, and have at most 11 pairs of walking legs as adults. Additionally, Hexamerocerata possess tracheae on the bases of first pair of legs, features lacking in all other pauropods. The body is colored white, and individuals are usually larger than in Tetramerocerata. Hexamerocerata are found in the tropics of Brazil, continental Africa, Madagascar, and Seychelles, as well as Japan.

Tetramerocerata is an order of pauropods containing 12 different families and about 480 different species. Tetrameroceratans have a 12 segmented body, 4 segmented antennae, 6 tergites, and 8-10 legs. They are generally 0.5 mm to 2 mm long. They are usually white or brown. Tetramerocerata has a subcosmopolitan distribution, occurring nearly worldwide.

Eopauropus balticus is a prehistoric pauropod known from mid-Eocene Baltic amber. It is the only known pauropod in the fossil record. As pauropods are normally soil-dwelling, their presence in amber is unusual, and they are the rarest known animals in Baltic amber.

<i>Scutigerella immaculata</i>

Scutigerella immaculata, commonly known as the garden symphylan or glasshouse symphylid, is a species of myriapod in the family Scutigerellidae. It may have originated in Europe but now has a cosmopolitan distribution and can be a pest of crops.

References

  1. Scheller, Ulf (2008). "A reclassification of the Pauropoda (Myriapoda)". International Journal of Myriapodology. 1 (1): 1–38. doi:10.1163/187525408X316730.
  2. Minelli, Alessandro (2011). "Class Chilopoda, Class Symphyla and Class Pauropoda. In: Zhang, Z.-Q. (Ed.) Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness" (PDF). Zootaxa . 3148: 157–158. doi:10.11646/zootaxa.3148.1.31.
  3. 1 2 Cedric Gillott (2005). Entomology (3rd ed.). Springer. ISBN   978-1-4020-3182-3.
  4. 1 2 David C. Coleman, D. A. Crossley, Jr. & Paul F. Hendrix (2004). Fundamentals of Soil Ecology (2nd ed.). Academic Press. p. 133. ISBN   978-0-12-179726-3.CS1 maint: multiple names: authors list (link)
  5. 1 2 "Subclass Pauropoda". what-when-how.com. Retrieved 2017-01-10.
  6. 1 2 3 Peter Ax (2000). "Pauropoda". Multicellular Animals: The phylogenetic system of the Metazoa. Volume 2 of Multicellular Animals: A New Approach to the Phylogenetic Order in Nature. Springer. pp. 231–233. ISBN   978-3-540-67406-1.
  7. Minelli, Alessandro (2011). The Myriapoda - Treatise on Zoology - Anatomy, Taxonomy, Biology. Brill Publishers. p. 495. ISBN   978-90-04-15611-1.

Further reading