Hyphomycetes are a

form classification Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships. Form classification, generally restricted to palaeontology, reflects uncertainty; the goal of sc ...

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

, part of what has often been referred to as fungi imperfecti, Deuteromycota, or

anamorph In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a fruiting body. *Anamorph: an ase ...

ic fungi. Hyphomycetes lack closed

fruit bodies The sporocarp (also known as fruiting body, fruit body or fruitbody) of fungi is a multicellular structure on which spore-producing structures, such as basidia or asci, are borne. The fruitbody is part of the sexual phase of a fungal life cyc ...

, and are often referred to as

mould A mold () or mould () is one of the structures that certain fungi can form. The dust-like, colored appearance of molds is due to the formation of spores containing fungal secondary metabolites. The spores are the dispersal units of the fungi ...

s (or molds). Most hyphomycetes are now mainly assigned to the

Ascomycota Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The def ...

, on the basis of genetic connections made by life-cycle studies or by

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analysis of

DNA sequence A nucleic acid sequence is a succession of bases within the nucleotides forming alleles within a DNA (using GACT) or RNA (GACU) molecule. This succession is denoted by a series of a set of five different letters that indicate the order of the nu ...

s; somemany remain unassigned phylogenetically. There are also some basidiomycete species, with aquatic presence noted in certain

Corticiaceae The Corticiaceae are a family of fungi in the order Corticiales. The family formerly included almost all the corticioid (patch- or crust-forming) fungi, whether they were related or not, and as such was highly artificial. In its current sense, ...

and Urediniomycetes. Although no longer considered a phylogenetically defined taxon, the prevalence of hyphomycete forms in nature, the built environment, and laboratories means that identification of members this group remains of practical importance.

Taxonomic and nomenclatural history

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 image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme o ...

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

) and the other for the sexual form (

teleomorph In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a fruiting body. *Anamorph: an ase ...

). 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 Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

including:

conidia A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also ...

l 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 A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...

-like,

phialide The phialide ( ; , diminutive of phiale, a broad, flat vessel) is a flask-shaped projection from the vesicle (dilated part of the top of conidiophore) of certain fungi. It projects from the mycelium without increasing in length unless a subsequ ...

, annellide, or

sympodial In botany, sympodial growth is a bifurcating branching pattern where one branch develops more strongly than the other, resulting in the stronger branches forming the primary shoot and the weaker branches appearing laterally. A sympodium, als ...

), 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 DNA barcoding is a method of species identification using a short section of DNA from a specific gene or genes. The premise of DNA barcoding is that by comparison with a reference library of such DNA sections (also called " sequences"), an indiv ...

. 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

, 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

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

s. Leaves with fungi (conditioned) are a more nutritious source of food for benthic

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s and

snail A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial molluscs, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gas ...

s than unconditioned leaves. Certain aquatic hyphomycetes are also found as mycoparasites, and biotrophs; like '' Naiadella fluitans'' and '' Gyoerffyella entomobryoides'', respectively. Common species include '' Articulospora tetracladia'' and '' Tetracladium marchalianum''. Coprophilous or dung-loving hyphomycetes are part of the

succession Succession is the act or process of following in order or sequence. Governance and politics *Order of succession, in politics, the ascension to power by one ruler, official, or monarch after the death, resignation, or removal from office of ...

of fungi occurring on many kinds of

herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

faeces, playing an important role in breaking down

cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important s ...

. Several species are found only on dung, such as '' Angulimaya sundara'', '' Onychophora coprophila'', '' Pulchromyces fimicola'', '' Sphondylocephalum verticillatum'' and '' Stilbella fimetaria''. Entomogenous, entomopathogenic or insect-pathogenic hyphomycetes infect and kill insects (and spiders) and are especially diverse in tropical and subtropical regions, especially in Asia. Most are asexual states of or phylogenetically related to the

Ascomycete Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The def ...

families,

Cordycipitaceae The Cordycipitaceae are a family of parasitic fungi in the Ascomycota, class Sordariomycetes and order Hypocreales. The family was first published in 1969 by mycologist Hanns Kreisel, but the naming was invalid according to the code of Internatio ...

and

Ophiocordycipitaceae Ophiocordycipitaceae is a family (biology), family of parasite, parasitic fungus, fungi in the phylum Ascomycota, class Sordariomycetes. It was created in 2007 to resolve the paraphyly of Calvicipitaceae. It was updated in 2020. Genera As accept ...

. Insect hosts are infected by asexual spores, which germinate and grow to fill the host body with

mycelium Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fo ...

, or hyphal bodies, and then produce sporulating structures on the insect carcass. They are often found on dead insects under bark or in soil, but some affect insect behaviour (" zombie fungus"), for example causing infected hosts to climb towards the light, ensuring that air-borne infective spores will be released higher up in the

canopy Canopy may refer to: Plants * Canopy (biology), aboveground portion of plant community or crop (including forests) * Canopy (grape), aboveground portion of grapes Religion and ceremonies * Baldachin or canopy of state, typically placed over an a ...

of the forest or meadow. Well-known entomogenous hyphomycetes are classified in '' Beauveria'', ''

Metarhizium ''Metarhizium'' is a genus (biology), genus of entomopathogenic fungus, entomopathogenic fungi in the family Clavicipitaceae. With the advent of genetic profiling, placing these fungi in proper taxa has now become possible. Most turn out to be ...

'' and '' Tolypocladium''; famous anamorphic generic names such as '' Akanthomyces'', '' Gibellula'', '' Hirsutella'', '' Hymenostilbe'' and '' Isaria'' are now subsumed in genera formerly considered sexual, such as ''

Cordyceps ''Cordyceps'' is a genus of ascomycete fungi (sac fungi) that includes over 260 species worldwide, many of which are parasitic. Diverse variants of cordyceps have had more than 1,500 years of use in Chinese medicine. Most ''Cordyceps'' specie ...

'', '' Ophiocordyceps'' and '' Torubiella'' under fungal single-name nomenclature. Species of ''Beauveria'' and ''Metarhizium'' show some promise as

biological control agent Biological control or biocontrol is a method of controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or plants by using other organisms. It relies on predation, parasitism, herbivory, or ot ...

s against pest insects. ''

Tolypocladium inflatum ''Tolypocladium inflatum'' is an ascomycete fungus originally isolated from a Norwegian soil sample that, under certain conditions, produces the immunosuppressant drug ciclosporin. In its sexual stage ( teleomorph) it is a parasite on scarab bee ...

'' was the original source of cyclosporine A, used as a drug to prevent rejection of

organ transplant Organ transplantation is a medical procedure in which an organ (anatomy), organ is removed from one body and placed in the body of a recipient, to replace a damaged or missing organ. The donor and recipient may be at the same location, or org ...

s. Many food-borne fungi are also hyphomycetes. Species of ''

Penicillium ''Penicillium'' () is a genus of Ascomycota, ascomycetous fungus, fungi that is part of the mycobiome of many species and is of major importance in the natural environment, in food spoilage, and in food and drug production. Some members of th ...

'' and ''

Aspergillus ' () is a genus consisting of several hundred mold species found in various climates worldwide. ''Aspergillus'' was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli. Viewing the fungi under a microscope, Miche ...

'' are particularly common agents of

food spoilage Food spoilage is the process whereby food becomes unsuitable to ingest by a person; it is a matter of food safety. Bacteria and various fungi are the causes of spoilage, and can create serious consequences for consumers, but there are preventive ...

and also produce important

mycotoxin A mycotoxin (from the Greek μύκης , "fungus" and τοξικός , "poisonous") is a toxic secondary metabolite produced by fungi and is capable of causing disease and death in both humans and other animals. The term 'mycotoxin' is usually rese ...

s that affect human health. Some species, such as '' Penicillium digitatum'' on citrus fruits, and ''

Penicillium expansum ''Penicillium expansum'' is a psychrophilic blue mold that is common throughout the world in soil. It causes Blue Mold of apples, one of the most prevalent and economically damaging post-harvest diseases of apples. Though primarily known as a ...

'' on apples, are common on specific foods, while others are less specialized and grow on many different kinds of food. Nematophagous or nematode-trapping hyphomycetes either live their life-cycles in the bodies of dead

nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...

s or trap and kill nematodes in order to supplement their

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

requirements. 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.

References

Literature

External links