Oribatida (formerly Cryptostigmata), also known asoribatid mites,moss mites orbeetle mites,[1] are anorder ofmites, in the "chewingAcariformes"cladeSarcoptiformes. 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]
Oribatid mites generally have lowmetabolic rates, slow development and low fecundity.[1] Species areiteroparous with adults living a relatively long time; for example, estimates of development time fromegg to adult vary from several months to two years intemperate forest soils.[1] Oribatid mites have six activeinstars: prelarva,larva, threenymphal instars and the adult.[1] All these stages after the prelarva feed on a wide variety of material including living and deadplant andfungal material,lichens andcarrion; some arepredatory, but none isparasitic 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 varioustapeworm species,[8] and by increasing the breakdown of organic material in the soil, in a similar manner toearthworms.[9]
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.[10]
For the majority of species, sperm transfer happens through stalkedspermatophores 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, andnuptial 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.[11]
In contrast to the commonly held view thatparthenogenetic lineages are short lived, four species-rich parthenogenetic clusters of the order Oribatida are very ancient and likely arose 400-300 million years ago.[12]Parthenogenetic oribatid mite lineages have been hypothesized to be adapted to occupy narrow specialized ecological niches.[13] However, it was recently shown that parthenogenetic oribatid mite species actually possess a widely adapted general-purposegenotype, and thus each such lineage might be viewed as a "jack-of-all-trades".[13]
TheAstigmatina, 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][14]
Oribatids have a long fossil record extending back to the middleDevonian, around 376-379 million years ago from Gilboa, New York, among the oldest known fossils of acariform mites.[15]
^Norton, Roy A.; Behan-Pelletier, Valerie M. (June 1991). "Calcium carbonate and calcium oxalate as cuticular hardening agents in oribatid mites (Acari: Oribatida)".Canadian Journal of Zoology.69 (6):1504–1511.Bibcode:1991CaJZ...69.1504N.doi:10.1139/z91-210.
^Denegri, G.M. Review of oribatid mites as intermediate hosts of tapeworms of the Anoplocephalidae. Exp Appl Acarol 17, 567–580 (1993).https://doi.org/10.1007/BF00053486
Halliday, R. B.; D. E. Walter; H. C. Proctor; R. A. Norton; M. J. Colloff, eds. (2001).Acarology, Proceedings of the 10th International Congress.Melbourne:CSIRO Publishing. pp. 1–960.ISBN0-643-06658-6.
