Oribatida

Oribatida (formerly Cryptostigmata), also known as oribatid mites, moss mites or beetle mites,[1] are an order of mites, in the "chewing Acariformes" clade Sarcoptiformes. They range in size from 0.2 to 1.4 millimetres (0.008 to 0.055 in).[1] There are currently 12,000 species that have been identified, but researchers estimate that there may be anywhere from 60,000 to 120,000 total species.[2] Oribatid mites are by far the most prevalent of all arthropods in forest soils, and are essential for breaking down organic detritus and distributing fungi.[3]

Oribatida Temporal range:
Unidentified mite (Phthiracaridae)
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Class:	Arachnida
Subclass:	Acari
Superorder:	Acariformes
Order:	Oribatida Dugès, 1833
Suborders
Brachypylina Enarthronota Holosomata Mixonomata Palaeosomata Parhyposomata
Diversity
c. 200 families, 1,200 genera, 6,600 species
Synonyms
Cryptostigmata

Oribatid mites generally have low metabolic rates, slow development and low fecundity.[1] Species are iteroparous with adults living a relatively long time; for example, estimates of development time from egg to adult vary from several months to two years in temperate forest soils.[1] Oribatid mites have six active instars: prelarva, larva, three nymphal instars and the adult.[1] All these stages after the prelarva feed on a wide variety of material including living and dead plant and fungal material, lichens and carrion; some are predatory, but none is parasitic and feeding habits may differ between immatures and adults of the same species. [4]

Many species have a mineralized exoskeleton as adults.[5][6] In some, this includes a pair of pteromorphae: wing-like flaps that overhang the legs on either side.[6] Some oribatids can also tuck in their legs underneath their protective armor, an ability known as ptychoidy, for more defence against predation.[6]

Alkaloids are produced by some oribatids, presumably as another defence against predation. In turn, poison dart frogs that prey on oribatids sequester these alkaloids for their own defence.[7]

The Oribatida are of economic importance as hosts of various tapeworm species, and by increasing the breakdown of organic material in the soil, in a similar manner to earthworms.[8]

Many species of oribatid mites require extremely specific habitats, resulting in large diversity within the order due to the many niches they evolve to. Some species are especially suited to dry conditions, or on bare lichen covered rocks, but that largest section of Oribatida prefers the moist forest floor and its accompanying litter. There are a small number of species who have evolved to live on aquatic plants, often spending the majority of their life submersed underwater.[9]

In contrast to the commonly held view that parthenogenetic lineages are short lived, four species-rich parthenogenetic clusters of the order Oribatida are very ancient and likely arose 400-300 million years ago.[10] Parthenogenetic oribatid mite lineages have been hypothesized to be adapted to occupy narrow specialized ecological niches.[11] However, it was recently shown that parthenogenetic oribatid mite species actually possess a widely adapted general-purpose genotype, and thus each such lineage might be viewed as a “jack-of-all-trades”.[11]

The Astigmatina, though once considered a separate group, are now considered part of Oribatida. They are quite different from other oribatids (e.g. many astigmatans are soft-bodied and some are parasitic), resulting in them often being treated separately.[6][12]