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.
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 sporotheca. Apart from riding on the beetles, the mites live together with them in their burrows in the wood.
These structures were first systematically described by Helene Francke-Grosmann at 1956. Then Lekh R. Batra coined the word mycangia: 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.
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. In the meantime, the fungus grows quickly in the galleries as the main food of beetle. The offsprings of beetle become mature, they will fill their mycangia with symbiont and hunt for the new host plant.
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. 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). Symbiotic fungi in mycangia of woodwasps are Amylostereaceae (Basidiomycota: Russulales). Symbiotic fungi in mycangia of lizard beetles are yeast (Ascomycota: Saccharomycetales). Symbiotic fungi in mycangia of ship-timber beetles are Endomyces (Ascomycota: Dipodascaceae). Symbiotic fungi in mycangia of leaf-rolling weevils are Penicillium fungi (Ascomycota: Trichocomaceae). In addition to the above primary symbiotic fungi, secondary fungi and some bacteria have been isolated from mycangia.
Mycangia of bark and ambrosia beetles (Curculionidae: Scolytinae and Platypodinae) are often complex cuticular invaginations for transport of symbiotic fungi. 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. These mycangia are often equipped with glands secreting substances to support fungal spores and perhaps to nourish mycelium during transport. 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, such as genus Ambrosiodmus and Euwallacea. Some are pronotal mycangia, such genus Xylosandrus and Cnestus.
Mycangia of the woodwasps (Hymenoptera: Siricidae) were first described by Buchner. 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.
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.
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. 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. 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.
Paleontology or palaeontology (from Greek: paleo, "ancient"; ontos, "being"; and logos, "knowledge") is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 2018.Euwallacea fornicatus
Euwallacea fornicatus is a species complex consisting of three cryptic species of ambrosia beetles (Coleoptera: Curculionidae: Scolytinae: Xyleborini), known as an invasive species in California, Israel and South Africa. As the rest of the ambrosia beetles, E. fornicatus larvae and adults feed on a symbiotic fungus carried in a specific structure called mycangium. In E. fornicatus, the mycangium is located in the mandible. The combination of massive numbers of beetles with the symbiotic fungus kill trees, even though the fungus alone is a weak pathogen.Euwallacea fornicatus breeds in various live hosts and is considered a severe pest of several economically important plants, such as: tea (Camellia sinensis), avocado (Persea americana), citrus (Citrus spp.) and cacao (Theobroma cacao).Platypus quercivorus
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.Raffaelea
Raffaelea is a genus of ambrosia fungi in the family Ophiostomataceae. It was cirumscribed by mycologists Josef Adolph von Arx and Grégoire L. Hennebert in 1965 with Raffaelea ambrosiae as the type species.Laurel wilt is a disease of redbay (Persea borbonia) caused by Raffaelea lauricola. This fungus, harbored in the mycangium of the redbay ambrosia beetle Xyleborus glabratus, is in the form of a budding yeast in the mycangium and a filamentous fungus in galleries of the beetle. Several species also resident in the beetle were described as new to science in 2010: R. ellipticospora, R. fusca, R. subalba, and R. subfusca.Sirex
Sirex is a genus of wasps in the family Siricidae, the horntails or wood wasps. They inject eggs with fungal endosymbionts into wood. The fungus is contained in a mycangium which nourishes it with secretions, and in turn it digests wood for the wasp larva.
The genus includes economically important pests; S. noctilio, known simply as the 'Sirex woodwasp' is an invasive species, having spread widely across the world from its original range.