The order Diplura ("two-pronged bristletails") is one of three orders of non-insect hexapods within the class Entognatha (alongside Collembola (

springtail Springtails (class Collembola) form the largest of the three lineages of modern Hexapoda, hexapods that are no longer considered insects. Although the three lineages are sometimes grouped together in a class called Entognatha because they have in ...

s) and Protura). The name "diplura", or "two tails", refers to the characteristic pair of caudal appendages or filaments at the terminal end of the body. Around 800 species of diplurans have been described.

Anatomy

Diplurans are typically long, with most falling between .Bugguide.net. Class Diplura - Two-pronged Bristletails
/ref> However, some species of '' Japyx'' may reach . They have no eyes and, apart from the darkened cerci in some species, they are unpigmented. Diplurans have long antennae with 10 or more bead-like segments projecting forward from the head. The abdomens of diplurans bear eversible vesicles, which seem to absorb moisture from the environment and help with the animal's water balance. The body segments themselves may display several types of setae, or scales and setae. Diplurans possess a characteristic pair of cerci projecting backwards from the last of the 11 abdominal somites. These cerci may be long and filamentous or short and pincer-like, leading to occasional confusion with earwigs. Some diplurans have the ability to shed their cerci if necessary ( autotomy). Moulting occurs up to 30 times throughout the life of a dipluran, which is estimated to last up to one year. As entognaths, the mouthparts are concealed within a small pouch by the lateral margins of the head capsule. The mandibles usually have several apical teeth. Diplurans do not possess any eyes or wings. In males, glandular setae or disculi may be visible along the first abdominal sternite. External genital organs are present on the eighth abdominal segment.

Ecology

Diplurans are common in moist

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

leaf litter Plant litter (also leaf litter, tree litter, soil litter, litterfall, or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that has fallen to the ground. This detritus or dead organic material and its constituen ...

humus In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Lati ...

, but are rarely seen because of their size and subterranean lifestyles. They have biting mouthparts and feed on a variety of live prey and dead organic matter. Those species with long cerci are herbivorous. Diplurans are found on nearly all land masses, except Antarctica and several oceanic islands. Their role as soil-dwelling organisms may play a key role in indicating soil quality, and as a measure of

anthropogenic Anthropogenic ("human" + "generating") is an adjective that may refer to: * Anthropogeny, the study of the origins of humanity Anthropogenic may also refer to things that have been generated by humans, as follows: * Human impact on the enviro ...

impact (e.g. soil nutrient depletion as a result of farming).

Reproduction

Like other non-insect hexapods, diplurans practice external fertilisation. Males lay up to 200 spermatophores a week, which are held off the ground by short stalks and probably only remain viable for about two days. The female collects the spermatophore with her genital opening, and later lays eggs in a cavity in the ground. The hatchlings (or

nymph A nymph (; ; sometimes spelled nymphe) is a minor female nature deity in ancient Greek folklore. Distinct from other Greek goddesses, nymphs are generally regarded as personifications of nature; they are typically tied to a specific place, land ...

s) do not undergo

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...

, but resemble the adults, apart from their smaller size, lesser number of setae and their lack of reproductive organs.

Lineages

Several major lineages within ''Diplura'' are readily recognizable by the structure of their cerci. * Japygidae: possess forceps-like cerci (resembling those of an earwig). Usually very aggressive predatory diplurans, using their pincer-like cerci to capture prey, including

s, isopods, small myriapods,

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e, and even other diplurans. *

Projapygidae The Projapygidae are a family of hexapods in the order Diplura. Genera * '' Biclavula'' San Martín, 1963 * '' Pentacladiscus'' San Martín, 1963 * '' Projapyx'' Cook, 1899 * '' Symphylurinus'' Silvestri, 1909 References Diplura Arthro ...

: possess stout, short, and rigid cerci. *

Campodeidae The Campodeidae are a family of hexapods belonging to the order Diplura. These pale, eyeless hexapods, the largest of which grow to around 12 mm in length, can be recognised by the two long, many-segmented cerci at the end of the abdomen. ...

: possess elongate, flexible cerci that may be as long as the antennae and have many segments. Feed on soil

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

mite Mites are small arachnids (eight-legged arthropods) of two large orders, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari. However, most recent genetic analyses do not recover the two as eac ...

s, springtails, and other small soil invertebrates, as well as detritus.

Relatives

The relationships among the four groups of hexapods are not resolved, but most recent studies argue against a

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

Entognatha. The

fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

of the Diplura is sparse, but one apparent dipluran dates from the

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

. This early dipluran, '' Testajapyx'', had

compound eye A compound eye is a Eye, visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidium, ommatidia, which are tiny independent photoreception units that consist of a cornea, lens (anatomy), lens, and p ...

s, and mouthparts that more closely resembled those of true insects.

References

External links

* {{Authority control Arthropod orders Extant Pennsylvanian first appearances