|Peacock mite ( Tuckerella sp.), false color SEM, magnified 260×|
|Cladistically included but traditionally excluded taxa|
Mites are small arthropods belonging to the class Arachnida and the subclass Acari (also known as Acarina). The term "mite" refers to the members of several groups in Acari but it is not a clade as it spans two different groups of arachnids; it also excludes the ticks, order Ixodida. Mites and ticks are characterised by the body being divided into two regions, the cephalothorax or prosoma (there is no separate head), and an opisthosoma. The scientific discipline devoted to the study of ticks and mites is called acarology.
An arthropod is an invertebrate animal having an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda, which includes insects, arachnids, myriapods, and crustaceans. The term Arthropoda as originally proposed refers to a proposed grouping of Euarthropods and the phylum Onychophora. Arthropods are characterized by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages. The rigid cuticle inhibits growth, so arthropods replace it periodically by moulting. Arthopods are bilaterally symmetrical and their body possesses an external skeleton. Some species have wings.
Arachnids are a class (Arachnida) of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata. Almost all adult arachnids have eight legs, although the front pair of legs in some species has converted to a sensory function, while in other species, different appendages can grow large enough to take on the appearance of extra pairs of legs. The term is derived from the Greek word ἀράχνη (aráchnē), from the myth of the hubristic human weaver Arachne who was turned into a spider. Spiders are the largest order in the class, which also includes scorpions, ticks, mites, harvestmen, and solifuges. In 2019, a molecular phylogenetic study also placed horseshoe crabs in Arachnida.
The Acari are a taxon of arachnids that contains mites and ticks. The diversity of the Acari is extraordinary and their fossil history goes back to at least the early Devonian period. Acarologists have proposed a complex set of taxonomic ranks to classify mites. In most modern treatments, the Acari are considered a subclass of the Arachnida and are composed of two or three superorders or orders: Acariformes, Parasitiformes, and Opilioacariformes; the latter is often considered a subgroup within the Parasitiformes. The monophyly of the Acari is open to debate, and the relationships of the acarines to other arachnids is not at all clear. In older treatments, the subgroups of the Acarina were placed at order rank, but as their own subdivisions have become better understood, treating them at the superorder rank is more usual.
Most mites are tiny, less than 1 mm (0.04 in) in length, and have a simple, unsegmented body plan. Their small size makes them easily overlooked; some species live in water, many live in soil as decomposers, others live on plants, sometimes creating galls, while others again are predators or parasites. This last group includes the commercially important Varroa parasite of honey bees, as well as the scabies mite of humans. Most species are harmless to humans but a few are associated with allergies or may transmit diseases.
Decomposers are organisms that break down dead or decaying organisms, and in doing so, they carry out the natural process of decomposition. Like herbivores and predators, decomposers are heterotrophic, meaning that they use organic substrates to get their energy, carbon and nutrients for growth and development. While the terms decomposer and detritivore are often interchangeably used, detritivores must ingest and digest dead matter via internal processes while decomposers can directly absorb nutrients through chemical and biological processes hence breaking down matter without ingesting it. Thus, invertebrates such as earthworms, woodlice, and sea cucumbers are technically detritivores, not decomposers, since they must ingest nutrients and are unable to absorb them externally.
Galls or cecidia are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to benign tumors or warts in animals. They can be caused by various parasites, from viruses, fungi and bacteria, to other plants, insects and mites. Plant galls are often highly organized structures and because of this the cause of the gall can often be determined without the actual agent being identified. This applies particularly to some insect and mite plant galls. The study of plant galls is known as cecidology.
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation and parasitoidism. It is distinct from scavenging on dead prey, though many predators also scavenge; it overlaps with herbivory, as a seed predator is both a predator and a herbivore.
The mites are not an exact taxon, but the name is used for members of several groups in the subclass Acari. The phylogeny of the Acari has been relatively little studied, but molecular information from ribosomal DNA is being extensively used to understand relationships between groups. The 18 S rRNA gene provides information on relationships among phyla and superphyla, while the ITS2, and the 18S ribosomal RNA and 28S ribosomal RNA genes, provide clues at deeper levels.
Ribosomal DNA (rDNA) is a DNA sequence that codes for ribosomal RNA. Ribosomes are assemblies of proteins and rRNA molecules that translate mRNA molecules to produce proteins. As shown in the figure, rDNA of eukaryotes consists of a tandem repeat of a unit segment, an operon, composed of NTS, ETS, 18S, ITS1, 5.8S, ITS2, and 28S tracts. rDNA has another gene, coding for 5S rRNA, located in the genome in most eukaryotes. 5S rDNA is also present in tandem repeats as in Drosophila. In the nucleus, the rDNA region of the chromosome is visualized as a nucleolus which forms expanded chromosomal loops with rDNA. These rDNA regions are also called nucleolus organizer regions, as they give rise to the nucleolus. In the human genome there are 5 chromosomes with nucleolus organizer regions: the acrocentric chromosomes 13 (RNR1), 14 (RNR2), 15 (RNR3), 21 (RNR4) and 22 (RNR5). In Bacteria, Archaea and chloroplasts the rRNA is composed of different (smaller) units, the large (23S) ribosomal RNA, 16S ribosomal RNA and 5S rRNA. The 16S rRNA is widely used for phylogenetic studies.
In biology, a phylum is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature for algae, fungi, and plants accepts the terms as equivalent. Depending on definitions, the animal kingdom Animalia or Metazoa contains approximately 35 phyla, the plant kingdom Plantae contains about 14, and the fungus kingdom Fungi contains about 8 phyla. Current research in phylogenetics is uncovering the relationships between phyla, which are contained in larger clades, like Ecdysozoa and Embryophyta.
Internal transcribed spacer (ITS) refers to the spacer DNA situated between the small-subunit ribosomal RNA (rRNA) and large-subunit rRNA genes in the chromosome or the corresponding transcribed region in the polycistronic rRNA precursor transcript.
The third edition (2009) of the standard textbook A Manual of Acarology uses a system of six orders, grouped into three superorders:
In biological classification, the order is
The Holothyrida are a small order of mites in the superorder Parasitiformes. No fossils are known. With body lengths of more than 2 mm they are relatively large mites, with a heavily sclerotized body. They mainly feed on the body fluids of dead arthropods. This was possibly the common way of feeding for ticks before they adapted for feeding on the blood of live animals.
Mesostigmata is an order of mites belonging to the Parasitiformes. Unlike most members of that group, many of these mites are not parasitic but free-living and predatory. They can be recognized by the single pair of spiracles positioned laterally on the body.
Opilioacariformes is the smallest order of mites, containing a single family, and around 10 genera. They are rare, large mites, and are widely considered primitive, as they retain six pairs of eyes, and abdominal segmentation. Opilioacariformes may be the sister group to the Parasitiformes.
The Opiliones are an order of arachnids colloquially known as harvestmen, harvesters, or daddy longlegs. As of April 2017, over 6,650 species of harvestmen have been discovered worldwide, although the total number of extant species may exceed 10,000. The order Opiliones includes five suborders: Cyphophthalmi, Eupnoi, Dyspnoi, Laniatores, and Tetrophthalmi, which were named in 2014.
Parasitiformes is an order of Acari. An alternative name is Anactinotrichida. Parasitiformes is one of two groups (orders) in Acari, the other being Acariformes (Actinotrichida).
Most fossil acarids are no older than the Tertiary (up to 65 mya).Earlier fossils are too few to enable mite phylogeny to be reconstructed from palaeontological evidence, but in 2002 an oribatid mite (Brachypylina) from the Early Ordovician (c. 480 mya) was found in Oland, Sweden. The first find of Parasitiformes from the Mesozoic was of an argasid tick larva in Cretaceous amber (90–94 mya) from New Jersey. Other fossils including the first opilioacariform mite are preserved in Baltic amber of Eocene age (44 mya).
Members of the superorders Opilioacariformes and Acariformes (sometimes known as Actinotrichida) are mites, as well as some of the Parasitiformes (sometimes known as Anactinotrichida).Recent genetic research has caused a change in the naming scheme, however, and recent publications have changed the superorder Parasitiformes to an order. Other recent research has suggested that Acari is polyphyletic (of multiple origins), with ticks and spiders more closely related than ticks and mites. The cladogram is based on Dabert et al 2010, which used molecular data. It shows the Acariformes sister to the Solifugae (camel spiders), while the Parasitiformes are sister to the Pseudoscorpionida.
" Acari "
(mites and ticks)
Mites are tiny members of the class Arachnida; most are in the size range 250 to 750 μm (0.01 to 0.03 in) but some are larger and some are no bigger than 100 μm (0.004 in) as adults. The body plan is similar to that of ticks in having two regions, a cephalothorax (with no separate head) or prosoma, and an opisthosoma or abdomen. Segmentation has almost entirely been lost and the prosoma and opisthosoma are fused, only the positioning of the limbs indicating the location of the segments.
At the front of the body is the gnathosoma or capitulum. This is not a head and does not contain the eyes or the brain, but is a retractable feeding apparatus consisting of the chelicerae, the pedipalps and the oral cavity. It is covered above by an extension of the body carapace and is connected to the body by a flexible section of cuticle. The mouthparts differ between taxa depending on diet; in some species the appendages resemble legs while in others they are modified into chelicerae-like structures. The oral cavity connects posteriorly to the mouth and pharynx.
Most mites have four pairs of legs, each with six segments, which may be modified for swimming or other purposes. The dorsal surface of the body is clad in hardened tergites and the ventral surface by hardened sclerites; sometimes these form transverse ridges. The gonopore (genital opening) is located on the ventral surface between the fourth pair of legs. Some species have one to five median or lateral eyes but many species are blind, and slit and pit sense organs are common. Both body and limbs bear setae (bristles) which may be simple, flattened, club-shaped or sensory. Mites are usually some shade of brown, but some species are red, orange, black or green, or some combination of these colours.
Mites have a typical arachnid digestive system, although some species lack an anus: they do not defecate during their short lives.The circulatory system consists of a network of sinuses and lacks a heart, movement of fluid being driven by the contraction of body muscles. Gas exchange is carried out across the body surface, but many species additionally have between one and four pairs of tracheae, the spiracles being located in the front half of the body. The excretory system includes a nephridium and one or two pairs of Malpighian tubules.
The sexes are separate in mites; males have a pair of testes in the mid-region of the body, each connected to the gonopore by a vas deferens, and in some species there is a chitinous penis; females have a single ovary connected to the gonopore by an oviduct, as well as a seminal receptacle for the storage of sperm. In most mites, sperm is transferred to the female indirectly; the male either deposits a spermatophore on a surface from which it is picked up the female, or he uses his chelicerae or third pair of legs to insert it into the female's gonopore. In some of the Acariformes, insemination is direct using the male's penis.
The eggs are laid in the substrate, or wherever the mite happens to live. They take from two to six weeks to hatch, and the first stage larvae have six legs. After three moults, the larvae become nymphs, with eight legs, and after a further three moults, they become adults. Longevity varies between species, but the lifespan of mites is short as compared to many other arachnids.
Mites occupy a wide range of ecological niches. For example, Oribatida mites are important decomposers in many habitats. They eat a wide variety of material including living and dead plant and fungal material, lichens and carrion; some are predatory, though no oribatid mites are parasitic.Mites are among the most diverse and successful of all invertebrate groups. They have exploited a wide array of habitats, and because of their small size go largely unnoticed. They are found in fresh and salt water, in the soil, in forests, pastures, agricultural crops, ornamental plants, thermal springs and caves. They inhabit organic debris of all kinds and are extremely numerous in leaf litter. They feed on animals, plants and fungi and some are parasites of plants and animals. Some 48,200 species of mites have been described, but there may be a million or more species as yet undescribed. The tropical species Archegozetes longisetosus is one of the strongest animals in the world, relative to its mass (100 μg): It lifts up to 1,182 times its own weight, over five times more than would be expected of such a minute animal. A mite also holds a speed record: for its length, Paratarsotomus macropalpis is the fastest animal on Earth.
Many mites are parasitic on plants and animals. One family of mites, Pyroglyphidae, or nest mites, live primarily in the nests of birds and animals. These mites are largely parasitic and consume blood, skin and keratin. Dust mites, which feed mostly on dead skin and hair shed from humans instead of consuming them from the organism directly, evolved from these parasitic ancestors.
Parasitic mites sometimes infest insects. Varroa destructor attaches to the body of honey bees, and Acarapis woodi (family Tarsonemidae) lives in their tracheae. Hundreds of species are associated with other bees, mostly poorly described. They attach to bees in a variety of ways. For example, Trigona corvina workers have been found with mites attached to the outer face of their hind tibiae.Some are thought to be parasites, while others are beneficial symbionts. Mites also parasitize some ant species, such as Eciton burchellii .
Plant pests include the so-called spider mites (family Tetranychidae), thread-footed mites (family Tarsonemidae), and the gall mites (family Eriophyidae).Among the species that attack animals are members of the sarcoptic mange mites (family Sarcoptidae), which burrow under the skin. Demodex mites (family Demodicidae) are parasites that live in or near the hair follicles of mammals, including humans.
Being unable to fly, mites need some other means of dispersal. On a small scale, walking is used to access other suitable locations in the immediate vicinity. Some species mount to a high point and adopt a dispersal posture and get carried away by the wind, while others waft a thread of silk aloft to balloon to a new position.
Parasitic mites use their hosts to disperse, and spread from host to host by direct contact. Another strategy is phoresy; the mite, often equipped with suitable claspers or suckers, grips onto an insect or other animal, and gets transported to another place. A phoretic mite is just a hitch-hiker and does not feed during the time it is carried by its temporary host. These travelling mites are mostly species that reproduce rapidly and are quick to colonise new habitats.
Mites are tiny, almost invisible, and apart from those that are of economic concern to humans, little studied. The majority are beneficial, living in the soil or aqueous environments and assisting in the decomposition of decaying organic material, or consuming fungi, plant or animal matter, as part of the carbon cycle.
The majority of mite species are harmless to humans and domestic animals, but a few species can colonize mammals directly, acting as vectors for disease transmission, and causing or contributing to allergenic diseases. Mites which colonize human skin are the cause of several types of itchy skin rashes, such as gamasoidosis,rodent mite dermatitis, grain itch, grocer's itch, and scabies; Sarcoptes scabiei is a parasitic mite responsible for scabies which is one of the three most common skin disorders in children. Demodex mites, which are common cause of mange in dogs and other domesticated animals, have also been implicated in the human skin disease rosacea, although the mechanism by which demodex contributes to the disease is unclear.
Chiggers are known primarily for their itchy bite, but they can also spread disease in some limited circumstances, such as scrub typhus.The house-mouse mite is the only known vector of the disease rickettsialpox. House dust mites, found in warm and humid places such as beds, cause several forms of allergic diseases, including hay fever, asthma and eczema, and are known to aggravate atopic dermatitis.
Among domestic animals, sheep are affected by the mite Psoroptes ovis which lives on the skin, causing hypersensitivity and inflammation.
The mite Varroa destructor is a serious pest of honey bees, contributing to colony collapse disorder in commercial hives. The mite is an obligate external parasite, able to reproduce only in bee colonies. It directly weakens its host by sucking up the bee's fat, and can spread RNA viruses including deformed wing virus. Heavy infestation causes the death of a colony, generally over the winter. Since 2006, over 10 million beehives have been lost.
Mites were first observed under the microscope by the English polymath Robert Hooke. In his 1665 book Micrographia , he stated that far from being spontaneously generated from dirt, they were "very prettily shap'd Insects".The world's first science documentary featured cheese mites, seen under the microscope; the short film was shown in London's Alhambra music hall in 1903, causing a boom in the sales of simple microscopes. A few years later, Arthur Conan Doyle wrote a satirical poem, Parable, with the conceit of some cheese mites disputing the origin of the round Cheddar cheese in which they all lived.
Ticks are small arachnids, typically 3 to 5 mm long, part of the order Parasitiformes. Along with mites, they constitute the subclass Acari. Ticks are ectoparasites, living by feeding on the blood of mammals, birds, and sometimes reptiles and amphibians. Ticks had evolved by the Cretaceous period, the most common form of fossilisation being immersed in amber. Ticks are widely distributed around the world, especially in warm, humid climates.
The Ixodidae are the family of hard ticks or scale ticks, one of the two big families of ticks, consisting of over 700 species. They are known as 'hard ticks' because they have a scutum or hard shield, which the other big family of ticks, the soft ticks (Argasidae), lack. They are ectoparasites of a wide range of host species, and some are vectors of disease.
Mange is a type of skin disease caused by parasitic mites. Because mites also infect plants, birds, and reptiles, the term "mange", suggesting poor condition of the hairy coat due to the infection, is sometimes reserved only for pathological mite-infestation of nonhuman mammals. Thus, mange includes mite-associated skin disease in domestic animals, in livestock, and in wild animals. Since mites belong to the arachnid subclass Acari, another term for mite infestation is acariasis.
Varroa destructor is an external parasitic mite that attacks the honey bees Apis cerana and Apis mellifera. The disease caused by the mites is called varroosis.
Varroa is a genus of parasitic mites associated with honey bees, placed in its own family, Varroidae. The genus was named for Marcus Terentius Varro, a Roman scholar and beekeeper. The condition of a honeybee colony being infested with Varroa mites is called varroosis.
Varroa jacobsoni is a species of mite that parasitises Apis cerana. The more damaging Varroa destructor was previously included under the name V. jacobsoni, but the two species can be separated on the basis of the DNA sequence of the cytochrome oxidase I gene in the mitochondrial DNA.
Acariasis is an infestation with mites.
The Acariformes, also known as the Actinotrichida, are the more diverse of the two superorders of mites. Over 32,000 described species are found in 351 families, and an estimated total of 440,000 to 929,000 species occur, including undescribed species.
Oribatida, also known as 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.
The Prostigmata is a suborder of mites belonging to the order Trombidiformes, which contains the "sucking" members of the "true mites" (Acariformes).
Trombiculidae are a family of mites. The best known of the Trombiculidae are the chiggers. The two widely recognized definitions of "chigger" are the scientific and the common, the latter of which can be found in English and medical dictionaries. According to most dictionaries, the several species of Trombiculidae that bite their host in their larval stage and cause "intense irritation" or "a wheal, usually with severe itching and dermatitis", are called chiggers. The scientific definition seemingly includes many more, but not all species of Trombiculidae.
Acomatacarus is a genus of mites in the family Trombiculidae. The larvae are parasitic. Species are called also chiggers, scrub itch-mite. The genus includes Acomatacarus arizonensis (lizards), Acomatacarus australiensis, Acomatacarus galli.
Flumethrin is a pyrethroid insecticide. It is used externally in veterinary medicine against parasitic insects and ticks on cattle, sheep, goats, horses, and dogs, and the treatment of parasitic mites in honeybee colonies.
Mites are small crawling animals related to ticks and spiders. Most mites are free-living and harmless. Other mites are parasitic, and those that infest livestock animals cause many diseases that are widespread, reduce production and profit for farmers, and are expensive to control.
Galumna pseudokhoii is a species of mite first found in Cát Tiên National Park, Vietnam, in dark loam in a Lagerstroemia forest. This species is very similar in the location and morphology of notogastral areae porosae, rostral morphology, lamellar and interlamellar setae, lamellar lines locations, and incomplete dorsosejugal suture to Galumna khoii, differing in body size, sensilli morphology, and the number of genital setae on the anterior parts of its genital plates.
Pergalumna indistincta is a species of mite first found in Cát Tiên National Park, Vietnam, in dark loam in a Lagerstroemia forest. This species is similar in notogastral areae porosae, punctate body surfaces, prodorsal setae morphology, and dorsosejugal suture, to Pergalumna amorpha, differing in body size and the development of its adanal setae.