The term mycangium (pl., mycangia) is used in biology for special structures on the body of an animal that are adapted for the transport of symbiotic fungi (usually in spore form). This is seen in many xylophagous insects (e.g. horntails and bark beetles), which apparently derive much of their nutrition from the digestion of various fungi that are growing amidst the wood fibers. In some cases, as in ambrosia beetles (Coleoptera: Curculionidae: Scolytinae and Platypodinae), the fungi are the sole food, and the excavations in the wood are simply to make a suitable microenvironment for the fungus to grow. In other cases (e.g., the southern pine beetle, Dendroctonus frontalis ), wood tissue is the main food, and fungi weaken the defense response from the host plant. [1]
Some species of phoretic mites that ride on the beetles, have their own type of mycangium, but for historical reasons, mite taxonomists use the term acarinarium. Apart from riding on the beetles, the mites live together with them in their burrows in the wood. [2] [3]
These structures were first systematically described by Helene Francke-Grosmann at 1956. [4] Then Lekh R. Batra [5] coined the word mycangia: [6] modern Latin, from Greek myco 'fungus' + angeion 'vessel'.
The most common function of mycangia is preserving and releasing symbiotic inoculum. Usually, the symbiotic inoculum in mycangia will benefit their vectors (typically insect or mites), helping them to adapt to the new environment or provide nutrients of the vectors themselves and their descendants. [7]
For example, the ambrosia beetle ( Euwallacea fornicatus ) carries the symbiotic fungus Fusarium . When the beetle bores a host plant, it releases the symbiotic fungus from its mycangium. The symbiotic fungus becomes a plant pathogen, acting to weaken the resistance of host plant. [8] In the meantime, the fungus grows quickly in the galleries as the main food of beetle. [8] After reproduction, maturing beetles will fill their mycangia with symbiont before hunting for a new host plant. [9]
Therefore, mycangia play an important role in protecting the inoculum from degradation and contamination. The structures of mycangia always resemble a pouch or a container, with caps or a small opening that reduce the possibility of contaminants from outside. [4] How mycangia release their inoculum is still unknown.
Most of the inoculum in mycangia are fungi. The symbiotic inoculum of most bark and ambrosia beetles are fungi belonging to Ophiostomatales (Ascomycota: Sordariomycetidae) and Microascales (Ascomycota: Hypocreomycetidae). [7] Symbiotic fungi in mycangia of woodwasps are Amylostereaceae (Basidiomycota: Russulales). [10] Symbiotic fungi in mycangia of lizard beetles are yeast (Ascomycota: Saccharomycetales). [11] Symbiotic fungi in mycangia of ship-timber beetles are Endomyces (Ascomycota: Dipodascaceae). [12] Symbiotic fungi in mycangia of leaf-rolling weevils are Penicillium fungi (Ascomycota: Trichocomaceae). [13] In addition to the above primary symbiotic fungi, secondary fungi and some bacteria have been isolated from mycangia. [14]
Mycangia of bark and ambrosia beetles (Curculionidae: Scolytinae and Platypodinae) are often complex cuticular invaginations for transport of symbiotic fungi. [2] [7] Phloem-feeding bark beetles (Curculionidae: Scolytinae) have usually numerous small pits on the surface of their body, while ambrosia beetles (many Scolytinae and all Platypodinae), which are completely dependent on their fungal symbiont, have deep and complicated pouches. [7] These mycangia are often equipped with glands secreting substances to support fungal spores and perhaps to nourish mycelium during transport. [15] In many cases, the entrance to a mycangium is surrounded by tufts of setae, aiding in scraping mycelium and spores from walls of the tunnels and directing the spores into the mycangium. The mycangia of ambrosia beetle are highly diverse. Different genera or tribes with different kinds of mycangia. Some are oral mycangia in the head, [7] such as genus Ambrosiodmus and Euwallacea . [16] Some are pronotal mycangia, such genus Xylosandrus and Cnestus. [17]
Mycangia of the woodwasps (Hymenoptera: Siricidae) were first described by Buchner. [18] Different from highly diverse types in bark and ambrosia beetles, woodwasps only have a pair of mycangia on the top of their ovipositor. Then when females deposit their eggs inside the host plant, they inject the symbiotic fungi from mycangia and phytotoxic mucus from another reservoir-like structure. [19]
One species of lizard beetle Doubledaya bucculenta (Coleoptera: Erotylidae: Erotylidae) has mycangia on the tergum of the eighth abdominal segment. This ovipositor-associated mycangia is only present in adult females. Before Doubledaya bucculentnta deposit their eggs and inject the symbiotic microorganisms on a recently dead bamboo, they will excavate a small hole through the bamboo culm. [11]
The ship-timber beetle (Coleoptera: Lymexylidae) is another family of wood-boring beetles that live with symbiotic fungi. Buchner first discovered their mycangia located on the ventral side of the long ovipositor. [20] These mycangia form a pair of integumental pouches at either side near the tip of oviduct. When the female lays the eggs, new eggs are coated with the fungal spores.
Females of the leaf-rolling weevil in the genus Euops (Coleoptera: Attelabidae) store symbiotic fungi in the mycangia, which is between the first ventral segment of the abdomen and the thorax. [13] Different from ovipositor-associate mycangia in woodwasps, lizard beetles, and ship-timber beetles, mycangia of leaf-rolling weevils is a pair of spore incubators at the anterior end of the abdomen. This mycangium is formed by the coxa and the metendosternite at the posterior end of the thorax. [10]
Mycangia of the stag beetles (Coleoptera: Lucanidae) were discovered in Japan only this century. [21] This ovipositor-associated mycangium is located in a dorsal fold of the integument between the last two tergal plates of the adult females. It has been examined in many species. [22] [23] [24] A female everts the mycangium for the first time soon after eclosion; this is to retrieve the symbionts left by the larva on the pupal chamber when it emptied its gut before pupating. Later, when ovipositing, she everts it to pass on the inoculum to the next generation. [25]
Ambrosia beetles are beetles of the weevil subfamilies Scolytinae and Platypodinae, which live in nutritional symbiosis with ambrosia fungi. The beetles excavate tunnels in dead or stressed trees into which they introduce fungal gardens, their sole source of nutrition. After landing on a suitable tree, an ambrosia beetle excavates a tunnel in which it releases its fungal symbiont. The fungus penetrates the plant's xylem tissue, extracts nutrients from it, and concentrates the nutrients on and near the surface of the beetle gallery. Ambrosia fungi are typically poor wood degraders, and instead utilize less demanding nutrients. Symbiotic fungi produce and detoxify ethanol, which is an attractant for ambrosia beetles and likely prevents growth of antagonistic pathogens and selects for other beneficial symbionts. The majority of ambrosia beetles colonize xylem of recently dead trees, but some colonize stressed trees that are still alive, and a few species attack healthy trees. Species differ in their preference for different parts of trees, different stages of deterioration, and in the shape of their tunnels ("galleries"). However, the majority of ambrosia beetles are not specialized to any taxonomic group of hosts, unlike most phytophagous organisms including the closely related bark beetles. One species of ambrosia beetle, Austroplatypus incompertus exhibits eusociality, one of the few organisms outside of Hymenoptera and Isoptera to do so.
A bark beetle is the common name for the subfamily of beetles Scolytinae. Previously, this was considered a distinct family (Scolytidae), but is now understood to be a specialized clade of the "true weevil" family (Curculionidae). Although the term "bark beetle" refers to the fact that many species feed in the inner bark (phloem) layer of trees, the subfamily also has many species with other lifestyles, including some that bore into wood, feed in fruit and seeds, or tunnel into herbaceous plants. Well-known species are members of the type genus Scolytus, namely the European elm bark beetle S. multistriatus and the large elm bark beetle S. scolytus, which like the American elm bark beetle Hylurgopinus rufipes, transmit Dutch elm disease fungi (Ophiostoma). The mountain pine beetle Dendroctonus ponderosae, southern pine beetle Dendroctonus frontalis, and their near relatives are major pests of conifer forests in North America. A similarly aggressive species in Europe is the spruce ips Ips typographus. A tiny bark beetle, the coffee berry borer, Hypothenemus hampei is a major pest on coffee plantations around the world.
The Lymexylidae, also known as ship-timber beetles, are a family of wood-boring beetles. Lymexylidae belong to the suborder Polyphaga and are the sole member of the superfamily Lymexyloidea.
Xyleborus glabratus, the redbay ambrosia beetle, is a type of ambrosia beetle invasive in the United States. It has been documented as the primary vector of Raffaelea lauricola, the fungus that causes laurel wilt, a disease that can kill several North American tree species in the family Lauraceae, including redbay, sassafras, and avocado.
Austroplatypus incompertus, a type of ambrosia beetle, is endemic to Australia. They are found in mesic forests, and subtropical and tropical ecosystems along the east coast of Australia. There are many unique characteristics attributable to the A. incompertus, like their gallery excavation in several Eucalyptus species, their obligate eusocial behavior, their relationship with fungi, and their unique sexual dimorphism. These beetles are one of the only insects that display obligate eusocial behavior. Additionally, their sexually dimorphic traits are of interest, since body size is reversed with males having smaller torsos than female A. incompertus beetles.
Euwallacea fornicatus, also known as tea shot-hole borer, or polyphagous shot-hole borer (PSHB) is a species complex consisting of multiple cryptic species of ambrosia beetles known as an invasive species in California, Israel, South Africa, and Australia. The species has also been unintentionally introduced into exotic greenhouses in several European countries.
Xyleborus affinis, the sugarcane shot-hole borer, is a species of ambrosia beetle in the family Curculionidae. It is found on all continents with woodlands and is one of the most widespread ambrosia beetles internationally, primarily in areas with humid tropical climates like Florida. Like other ambrosia beetles, Xyleborus affinis is attracted to dead fallen logs in early stages of decay. Due to the presence of X. affinis on moist timber, this species is mistakenly believed to be the cause of tree death. However, there is insufficient evidence to support their presence as a causal factor. Rather, these beetles are believed to target and accelerate the decay process of trees that are already deteriorated and weak.
Xylosandrus germanus, known generally as the alnus ambrosia beetle or black stem borer, is a species of ambrosia beetle in the family Curculionidae. X. germanus poses challenges in woody ornamental species and orchard crops such as apples and pecan. Furthermore, X. germanus is recognized or suspected to act as a vector for plant pathogens to varying extents, potentially leading to the decline of trees. The black stem borer is native to eastern Asia, but is an invasive species in Europe and North America. This species carries and feeds on associated ambrosia fungus, Ambrosiella grosmanniae.
Xyleborinus saxesenii, commonly known as the fruit-tree pinhole borer, is a species of ambrosia beetle in the family Curculionidae. It is native to the Palaearctic region but has been introduced in many locations, including North America. X. saxesenii typically live in freshly dead wood, but it has also been reported to attack live trees. Such attacks on live trees may lead to economic damage.
Platypus quercivorus, the oak ambrosia beetle, is a species of weevil and pest of broad-leaved trees. This species is most commonly known for vectoring the fungus responsible for excessive oak dieback in Japan since the 1980s. It is found in Japan, India, Indonesia, New Guinea, and Taiwan.
Cnestus mutilatus, commonly known as the camphor shot borer, camphor shoot borer, or sweetgum ambrosia beetle, is a species of ambrosia beetle in the subfamily Scolytinae of the weevil family Curculionidae. It is native to Asia, but has been established as an invasive species in the United States since 1999.
Xyleborus dispar is a species of bark beetle commonly called the Pear blight beetle, or the European shothole borer. It is an invasive species in North America, and can be a pest in orchards and forests throughout its range.
Fungus pockets are any of various convergently evolved inoculum-retention and -cultivation organs in a wide range of insect taxa. They are generally divided into mycangia and infrabuccal pockets.
Euwallacea interjectus is a species of ambrosia beetle in the species complex called Euwallacea fornicatus. It is native to Asia but has been introduced to the Western hemisphere over the last century.
Euwallacea perbrevis, commonly known as tea shot-hole borer, is a species of weevil native to South and South-East Asia through to Australia, but introduced to Western countries.
Dorcus hopei is a beetle in the family Lucanidae.
Ambrosiella roeperi is the fungal symbiont of the granulate ambrosia beetle, Xylosandrus crassiusculus, facilitating this insect’s capacity to accumulate on and damage a diverse array of woody plants from around the world. It is one of several important nutritional partners derived from order Microascales that sustain and are transported by xylomycetophagous scolytine beetles.
Cryphalus mangiferae, the mango bark beetle, is a tiny tropical bark beetle which attacks mango trees. The species belongs to the family Curculionidae, subfamily Scolytinae. It is often cited as a vector of plant pathogenic fungi infecting mango trees and in some countries like Pakistan it is regarded as a serious threat to mango cultivation.
Euwallacea validus is a species of Euwallacea beetle native to Asia. The beetle species was discovered in Long Island, New York in 1975. Like other Euwallacea species beetles, E. validus is known for its mutualistic symbiotic relationship with fungi, acting as a vector for Fusarium oligoseptatum and Raffaelea subfusca, often using Tree of Heaven as a preferred host. Out of the five confirmed species of Euwallacea spp. in the United States, E. validus is the most widespread and longest established, yet much about their second fungal partner, Raffaelea subfusca, is not known.
Euwallacea is a genus of typical bark beetles in the family Curculionidae. They are commonly known as Ambrosia beetles, as all species are symbiotic with Ambrosia fungi. Originally from Asia or Wallacea, they are now found worldwide. Many species are pests, causing damage to, or the death of, tree species valued for their fruit or timber.
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