Diplura

The order Diplura ("two-pronged bristletails") is one of three orders of non-insect hexapods within the class Entognatha (alongside Collembola (springtails) and Protura).<ref name="Massey">Template:Cite web</ref> 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

File:Campodeidae sp. (11499938054).jpg

A dipluran of the family Campodeidae

Diplurans are typically Template:Convert long, with most falling between Template:Convert.<ref name=":0">Bugguide.net. Class Diplura - Two-pronged Bristletails</ref> However, some species of Japyx may reach Template:Convert.<ref name="Kendall">Template:Cite web</ref> They have no eyes and, apart from the darkened cerci in some species, they are unpigmented.<ref name="Kendall"/> Diplurans have long antennae with 10 or more bead-like segments projecting forward from the head.<ref name="McMaster">Template:Cite web</ref> The abdomens of diplurans bear eversible vesicles, which seem to absorb moisture from the environment and help with the animal's water balance.<ref name="McMaster" /> The body segments themselves may display several types of setae, or scales and setae.<ref name=":1">Template:Cite journal</ref>

Diplurans possess a characteristic pair of cerci projecting backwards from the last of the 11 abdominal somites.<ref name="Earthlife">Template:Cite web</ref> These cerci may be long and filamentous or short and pincer-like,<ref name="Iziko">Template:Cite web</ref> leading to occasional confusion with earwigs.<ref name="CSIRO">Template:Cite web</ref> 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.<ref name=":1" /> Diplurans do not possess any eyes or wings.<ref name=":0" />

In males, glandular setae or disculi may be visible along the first abdominal sternite. External genital organs are present on the eighth abdominal segment.<ref name=":1" />

Ecology

Diplurans are common in moist soil, leaf litter or humus,<ref name="NCSU">Template:Cite web</ref> but are rarely seen because of their size and subterranean lifestyles.<ref name="McMaster"/> They have biting mouthparts and feed on a variety of live prey and dead organic matter.<ref name="Massey"/> Those species with long cerci are herbivorous.<ref name="CSIRO"/>

Diplurans are found on nearly all land masses, except Antarctica and several oceanic islands.<ref name=":1" /> Their role as soil-dwelling organisms may play a key role in indicating soil quality, and as a measure of anthropogenic impact (e.g. soil nutrient depletion as a result of farming).<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

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.<ref name="NCSU"/> The female collects the spermatophore with her genital opening, and later lays eggs in a cavity in the ground.<ref name="CSIRO"/><ref name="McMaster"/><ref name="NCSU"/> The hatchlings (or nymphs) do not undergo metamorphosis, but resemble the adults, apart from their smaller size, lesser number of setae and their lack of reproductive organs.<ref name="Massey"/>

Lineages

File:Diplura Campodea Japyx.jpg

Anatomy of Campodea (Campodeidae) and Japyx (Japygidae)

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 springtails, isopods, small myriapods, insect larvae, and even other diplurans.<ref name="Massey" />
• Projapygidae: possess stout, short, and rigid cerci.<ref>Template:Cite journal</ref>
• Campodeidae: possess elongate, flexible cerci that may be as long as the antennae and have many segments. Feed on soil fungi, mites, springtails, and other small soil invertebrates, as well as detritus.<ref name="Massey" />

Relatives

The relationships among the four groups of hexapods are not resolved, but most recent studies argue against a monophyletic Entognatha.<ref name="Carapelli">Template:Cite journal</ref> The fossil record of the Diplura is sparse, but one apparent dipluran dates from the Carboniferous.<ref name="TOL"/> This early dipluran, Testajapyx, had compound eyes, and mouthparts that more closely resembled those of true insects.

External links

• Template:Wikispecies-inline