Oribatida (formerly Cryptostigmata), also known as oribatid mites, moss mites or beetle mites, 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). 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. 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.

Oribatid mites generally have low metabolic rates, slow development and low fecundity. 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. Oribatid mites have six active instars: prelarva, larva, three nymphal instars and the adult. 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.

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

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.

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.

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.

For the majority of species, sperm transfer happens through stalked spermatophores placed on the substrate by the male, which is then picked up by the female. Yet, in a few species, courtship behavior occurs, such as a 'promenade à deux' where the male leads the female, and nuptial gifts in the form of male secretions have been reported (e.g., in Collohmannia). In species such as Fortuynia atlantica, it is suspected that the male deposits a stalkless spermatophore during courtship and then leads the female over it, but this has never been directly observed. The only observation of a more direct sperm transfer is in a species of the genus Pilogalumna. Instead of courtship behavior, the male forcefully attaches a stalkless spermatophore close to the female's genital plate.

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. Parthenogenetic oribatid mite lineages have been hypothesized to be adapted to occupy narrow specialized ecological niches. 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".

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.

Oribatids have a long fossil record extending back to the middle Devonian, around 376-379 million years ago from Gilboa, New York, among the oldest known fossils of acariform mites.

Systematics

The order Oribatida is divided into the following taxa:

  • Palaeosomata Grandjean, 1969

Acaronychoidea Grandjean, 1932 (6 genera) Acaronychidae Grandjean, 1932

Palaeacaroidea Grandjean, 1932 (8 genera) Palaeacaridae Grandjean, 1932

  • Parhyposomata Balogh & Mahunka, 1979

Parhypochthonioidea Grandjean, 1969 (3 genera) Parhypochthoniidae Grandjean, 1969 Gehypochthoniidae Strenzke, 1963 Elliptochthoniidae Norton, 1975

Hypochthonoidea Berlese, 1910 (c. 8 genera) Hypochthoniidae Berlese, 1910 Eniochthoniidae Grandjean, 1947 Arborichthoniidae Balogh & Balogh, 1992

Brachychthonoidea Thor, 1934 (c. 11 genera) Brachychthoniidae Thor, 1934

Cosmochthonioidea Grandjean, 1947 (c. 14 genera) Cosmochthoniidae Grandjean, 1947 Heterochthoniidae Grandjean, 1954 Haplochthoniidae Hammen, 1959 Pediculochelidae Lavoipierre, 1946 Sphaerochthoniidae Grandjean, 1947

Atopochthonioidea Grandjean, 1949 (3 genera) Atopochthoniidae Grandjean, 1949 Pterochthoniidae Grandjean, 1950 Phyllochthoniidae Travé, 1967

Protoplophoroidea Ewing, 1917 (c. 7 genera) Protoplophoridae Ewing, 1917

  • Mixonomata Grandjean, 1969

Dichosomata Balogh & Mahunka, 1979

Nehypochthonioidea Norton & Metz, 1980 Nehypochthoniidae Norton & Metz, 1980

Perlohmannioidea Grandjean, 1954 Perlohmaniidae Grandjean, 1954 Collohmanniidae Grandjean, 1958

Eulohmannioidea Grandjean, 1931 Eulohmanniidae Grandjean, 1931

Epilohmannioidea Oudemans, 1923 Epilohmanniidae Oudemans, 1923

Lohmannioidea Berlese, 1916 Lohmanniidae Berlese, 1916

Euptyctima Grandjean, 1967

Mesoplophoroidea Ewing, 1917 Mesoplophoridae Ewing, 1917

Euphthiracaroidea Jacot, 1930 Oribotritiidae Grandjean, 1954 Euphthiracaridae Jacot, 1930 Synichotritiidae Walker, 1965

Phthiracaroidea Perty, 1841 Phthiracaridae Perty, 1841 Steganacaridae Niedbała, 1986

  • Holosomata Grandjean, 1969

Crotonioidea Thorell, 1876 Thrypochthoniidae Willmann, 1931 Malaconothridae Berlese, 1916 Nothridae Berlese, 1896 Camisiidae Oudemans, 1900 Crotoniidae Thorell, 1876

Nanhermannioidea Sellnick, 1928 Nanhermanniidae Sellnick, 1928

Hermannioidea Sellnick, 1928 Hermanniidae Sellnick, 1928

Pycnonoticae Grandjean, 1954 Hermannielloidea Grandjean, 1934 (2 families) Neoliodoidea Sellnick, 1928 (1 family) Plateremaeoidea Trägårdh, 1926 (4 families) Gymnodamaeoidea Grandjean, 1954 (2 families) Damaeoidea Berlese, 1896 (1 family) Polypterozetoidea Grandjean, 1959 (2 families) Cepheoidea Berlese, 1896 (7 families) Charassobatoidea Grandjean, 1958 (3 families) Microzetoidea Grandjean, 1936 (1 family) Zetorchestoidea Michael, 1898 (1 family) Gustavioidea Oudemans, 1900 (8 families) Eremaeoidea Oudemans, 1900 (4 families) Amerobelboidea Grandjean, 1954 (10 families) Eremelloidea Balogh, 1961 (7 families) Oppioidea Sellnick, 1937 (12 families) Trizetoidea Ewing, 1917 (6 families) Otocepheoidea Balogh, 1961 (4 families) Carabodoidea Koch, 1837 (3 families) Tectocepheoidea Grandjean, 1954 (2 families) Hydrozetoidea Grandjean, 1954 (1 family) Ameronothroidea Willmann, 1931 (3 families) Cymbaeremaeoidea Sellnick, 1928 (3 families)

Poronoticae Grandjean, 1954 Licneremaeoidea Grandjean, 1931 (6 families) Phenopelopoidea Petrunkevitch, 1955 (1 family) Unduloribatoidea Kunst, 1971 (3 families) Limnozetoidea Thor, 1937 (2 families) Achipterioidea Thor, 1929 (2 families) Oribatelloidea Jacot, 1925 (3 families) Ceratozetoidea Jacot, 1925 (5 families) Zetomotrichoidea Grandjean, 1934 (1 family) Oripodoidea Jacot, 1925 (19 families) Galumnoidea Jacot, 1925 (3 families)

See also

Further reading