Hyphomycetes

Because asexual forms of fungi usually occur separately from their sexual forms, when microscopic fungi began to be studied in the early 19th century, it was often unknown when two morphologically different forms were actually part of one species. The tendency for some organisms to apparently only have asexual forms, or for their sexual forms to be discovered long after the asexual forms, meant that an independent taxonomy was developed for asexual fungi. Near the beginning of the 20th century, when it became clearer that many asexual and sexual forms were related, the concept of 'form taxa' was developed. The independent taxonomy of asexual forms was regarded as artificial, not representative of evolutionary relationships, and intended to be practical for identification purposes. The taxonomy of the sexual states was considered the true classification. The result was that many fungal species ended up with two accepted Latin binomials, one for the asexual form (or anamorph) and the other for the sexual form (teleomorph). This dual nomenclature was only abandoned in January 2012, and the transition to a single name system, with one name representing all morphs of a fungus, is still incomplete. ==Identification==

Traditional identification of hyphomycetes was primarily based on microscopic morphology including: conidial morphology, especially septation, shape, size, colour and cell wall texture, the arrangement of conidia as they are borne on the conidiogenous cells (e.g. if they are solitary, in chains, or produced in slime), the type of conidiogenous cell (e.g. non-specialized or hypha-like, phialide, annellide, or sympodial), and other additional features such as the presence of sporodochia or synnemata. For species growing in culture, or in environmental DNA studies, most identifications of Hyphomycetes are now done with DNA barcoding. This is not always possible, however, for archival specimens or samples such as microscopic slides from air samples. ==Ecological importance==

Aquatic hyphomycetes or Ingoldian hyphomycetes are common on submerged decaying leaves and other organic matter, especially in clean running water with good aeration. Colonised leaves fall from the tree into the river. Their branched, septate mycelium penetrates through the leaf surface and spreads through leaf tissue. Conidiophores project into the water and bear conidia, which are often sigmoid, branched or tetraradiate structures. Aquatic hyphomycetes play an important role in the breakdown of organic matter in rivers, because their extracellular enzymes break down leaf tissue, which in turn is made more palatable to invertebrates. Leaves with fungi (conditioned) are a more nutritious source of food for benthic insects and snails than unconditioned leaves. Species of the hyphomycete genus Arthrobotrys, phylogenetically related to - or being the asexual forms of Orbilia - produce constricting loops that quickly shut to grab nematodes, or non-constricting loops or hyphal networks that entangle nematodes, or sticky knobs that adhere to nematodes as they swim by. Attempts to exploit these fungi as biological control agents against agriculturally harmful nematodes have generally been unsuccessful. ==See also==