Orbiliaceae
Encyclopedia
The Orbiliaceae are a family
of saprobic sac fungi in the order
Orbiliales. The family, first described by Nannfield in 1932, contains 288 species
in 12 genera
. Members of this family have a widespread distribution, but are more prevalent in temperate
regions. Some species in the Orbiliaceae are carnivorous fungi, and have evolved a number of specialized mechanisms to trap nematode
s.
, dense structural tissue that produces fruit bodies. They have small disc-shaped apothecia, that are typically convex, brightly colored or translucent. Their ascospore
s are small (typically less than 10 x 1 µm
), hyaline
, and have an oval or ellipsoidal shape.
Species are usually found in wood on both wet and dry habitats.
Anamorph species are hyphomycetous
.
species. Shortly after coming into contact with its prey, fungal mycelia penetrate the nematode and spontaneously differentiate into functional structures, known as traps, which will ultimately digest the nematode's internal contents. There are 5 types of trap mechanisms recognized in this family:
and the Orbilia
. Hyalorbilia is distinguished from Orbilia by having asci
without a stalk that arise from croziers, a hemispherical to broadly conical, thin-walled apex, asci and paraphyses
in a gelatinous matrix, and an ectal excipulum (the outer surface of a cup-like apothecium) of horizontal textura prismatica.
Anamorph genera of the Orbiliaceae include Anguillospora, Arthrobotrys
, Dactylella
, Dactylellina
, Dicranidion
, Drechslerella, Helicoön, Monacrosporium
, and Trinacrium. It has been suggested that the anamorph specialization illustrates convergent evolution
occurring among mycelial fungi in aquatic and low-nitrogen
habitats. This hypothesis has been borne out by recent phylogenetic and morphological studies.
In 2007, a new species was described from southwestern China with morphological features intermediate between Orbilia and Hyalorbilia. This species, named Pseudorbilia bipolaris Y. Zhang, Z.F. Yu, H.O. Baral & K.Q. Zhang, was placed into its own genus in the Orbiliaceae to accommodate its distinctive features.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of saprobic sac fungi in the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Orbiliales. The family, first described by Nannfield in 1932, contains 288 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in 12 genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
. Members of this family have a widespread distribution, but are more prevalent in temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
regions. Some species in the Orbiliaceae are carnivorous fungi, and have evolved a number of specialized mechanisms to trap nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
s.
Description
Orbiliaceae do not have stromataEpichloë
Epichloë species and their close relatives, the Neotyphodium species, are systemic and constitutive symbionts of cool-season grasses , and belong to the fungal family Clavicipitaceae...
, dense structural tissue that produces fruit bodies. They have small disc-shaped apothecia, that are typically convex, brightly colored or translucent. Their ascospore
Ascospore
An ascospore is a spore contained in an ascus or that was produced inside an ascus. This kind of spore is specific to fungi classified as ascomycetes ....
s are small (typically less than 10 x 1 µm
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
), hyaline
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...
, and have an oval or ellipsoidal shape.
Species are usually found in wood on both wet and dry habitats.
Anamorph species are hyphomycetous
Hyphomycetes
Hyphomycetes is an obsolete class of fungi in the equally obsolete phylum Deuteromycota that lack fruiting bodies. Most hyphomycetes have now been assigned to the Ascomycota, mainly as a result of DNA sequencing, but many remain unassigned...
.
Nematophagy
This family is well-known for its many nematophagousNematophagous fungus
Nematophagous fungi are carnivorous fungi specialized in trapping and digesting nematodes. Around 160 species are known. There exist both species that live inside the nematodes from the beginning and others that catch them mostly with glue traps or in rings, some of which constrict on contact. Some...
species. Shortly after coming into contact with its prey, fungal mycelia penetrate the nematode and spontaneously differentiate into functional structures, known as traps, which will ultimately digest the nematode's internal contents. There are 5 types of trap mechanisms recognized in this family:
- Adhesive network: the most common trap, formed by hyphaHyphaA hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
l outgrowths that recurve into themselves to form nematode-trapping loops. - Adhesive knob: a roughly spherical cell, attached to the hyphae either directly or on an erect stalk. Adhesive knobs are typically closely spaced along a section of hyphae.
- Nonconstricting rings: always found with the adhesive network traps, and formed from thickening hyphae that curve and fuse to the supporting stalk.
- Adhesive column: a layer of cells on a hyphae with an adhesive surface.
- Constricting rings: these are rings of hyphae that swell rapidly inwards upon contact with the nematode, quickly (in 1–2 seconds) "lassoLassoA lasso , also referred to as a lariat, riata, or reata , is a loop of rope that is designed to be thrown around a target and tighten when pulled. It is a well-known tool of the American cowboy. The word is also a verb; to lasso is to successfully throw the loop of rope around something...
ing" the victim.
Genera
According to the most recent classification of Ascomycota, the Orbiliaceae contain only two (teleomorph) genera, the HyalorbiliaHyalorbilia
Hyalorbilia is a genus comprising 10 species of fungi in the family Orbiliaceae.-Species:*Hyalorbilia arcuata Baral, M.L. Wu & Y.C. Su 2007*Hyalorbilia berberidis Baral 2000*Hyalorbilia biguttulata Baral, M.L. Wu & Y.C. Su 2007...
and the Orbilia
Orbilia
The Orbilia are a genus of fungi in the family Orbiliaceae. Anamorphs of this genus include the Arthrobotrys, Dactylella, Dicranidion, Dwayaangam, Helicoön, Monacrosporium, and Trinacrium....
. Hyalorbilia is distinguished from Orbilia by having asci
Ascus
An ascus is the sexual spore-bearing cell produced in ascomycete fungi. On average, asci normally contain eight ascospores, produced by a meiotic cell division followed, in most species, by a mitotic cell division. However, asci in some genera or species can number one , two, four, or multiples...
without a stalk that arise from croziers, a hemispherical to broadly conical, thin-walled apex, asci and paraphyses
Paraphyses
Paraphyses are part of the fertile spore-bearing layer in certain fungi. More specifically, paraphyses are sterile filamentous hyphal end cells composing part of the hymenium of Ascomycota and Basidiomycota interspersed among either the asci or basidia respectively, and not sufficiently...
in a gelatinous matrix, and an ectal excipulum (the outer surface of a cup-like apothecium) of horizontal textura prismatica.
Anamorph genera of the Orbiliaceae include Anguillospora, Arthrobotrys
Arthrobotrys
Arthrobotrys is a genus of mitosporic fungi in the family Orbiliaceae. There are 71 species.-Species:*Arthrobotrys aggregata Mekht. 1979*Arthrobotrys alaskana Matsush.) Oorschot 1985...
, Dactylella
Dactylella
Dactylella is a genus comprising 72 species of mitosporic fungi in the family Orbiliaceae. They are notable for trapping and eating nematodes.-Species:*Dactylella acrochaeta Drechsler 1952*Dactylella alaskana Matsush. 1975...
, Dactylellina
Dactylellina
Dactylellina is a genus mitosporic fungi in the family Orbiliaceae. There are 15 species.-Species:*Dactylellina arcuata Ying Yang & Xing Z. Liu 2006*Dactylellina candida Yan Li 2005...
, Dicranidion
Dicranidion
Dicranidion is a genus comprising 13 species of fungi in the family Orbiliaceae.-Species:*Dicranidion amazonense Matsush. 1981*Dicranidion argentinense Speg. 1910*Dicranidion dactylopagum Peek & Solheim 1955...
, Drechslerella, Helicoön, Monacrosporium
Monacrosporium
Monacrosporium is a genus of fungi in the family Orbiliaceae. There are 53 species.-Species:*Monacrosporium ambrosium Gadd & Loos 1947*Monacrosporium aphrobrochum Subram. 1964...
, and Trinacrium. It has been suggested that the anamorph specialization illustrates convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
occurring among mycelial fungi in aquatic and low-nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
habitats. This hypothesis has been borne out by recent phylogenetic and morphological studies.
In 2007, a new species was described from southwestern China with morphological features intermediate between Orbilia and Hyalorbilia. This species, named Pseudorbilia bipolaris Y. Zhang, Z.F. Yu, H.O. Baral & K.Q. Zhang, was placed into its own genus in the Orbiliaceae to accommodate its distinctive features.
External links
- Orbilia at Index FungorumIndex FungorumIndex Fungorum, an international project to index all formal names in the Fungi Kingdom. Somewhat comparable to the IPNI, but with more contributing institutions....
- Images of various Orbilia and Hyalorbilia species
- Videos of Arthrobotrys oligospora trapping nematodes