Hydnaceae
Encyclopedia
The Hydnaceae are a family
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 fungi in the order Cantharellales
Cantharellales
The Cantharellales are an order of fungi in the class Agaricomycetes. The order includes not only the chanterelles , but also some of the tooth fungi , clavarioid fungi , and corticioid fungi...

. Originally the family encompassed all 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...

 of fungi that produced basidiocarps (fruit bodies) having a hymenium
Hymenium
The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in others some cells develop into sterile cells called cystidia or...

 (spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...

-bearing surface) consisting of slender, downward-hanging tapering extensions referred to as "spines" or "teeth", whether they were related or not. This artificial but often useful grouping is now more generally called the hydnoid or tooth fungi
Hydnoid fungi
The hydnoid fungi are a group of fungi in the Basidiomycota with basidiocarps producing spores on pendant, tooth-like or spine-like projections. They are colloquially called tooth fungi...

. In the strict, modern sense, the Hydnaceae are limited to the genus
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...

 Hydnum
Hydnum
Hydnum is a genus of fungi in the Hydnaceae family. They are notable for their unusual spore-bearing structures of teeth rather than gills. The best known are the edible species Hydnum repandum and H. rufescens. The word is derived from udnon/ύδνον, an Ancient Greek word for truffle...

and related genera, with basidiocarps having a toothed or poroid
Polypore
Polypores are a group of tough, leathery poroid mushrooms similar to boletes, but typically lacking a distinct stalk. The technical distinction between the two types of mushrooms is that polypores do not have the spore-bearing tissue continuous along the entire underside of the mushroom. Many...

 hymenium. Species in the family are ectomycorrhizal, forming a mutually beneficial relationship with the roots of trees and other plants. Hydnum repandum (the hedgehog fungus) is an edible
Edible mushroom
Edible mushrooms are the fleshy and edible fruiting bodies of several species of fungi. Mushrooms belong to the macrofungi, because their fruiting structures are large enough to be seen with the naked eye. They can appear either below ground or above ground where they may be picked by hand...

 species, commercially collected in some countries and often marketed under the French name "pied de mouton".

History

The family was originally described in 1826 by French botanist François Fulgis Chevallier to accommodate all the larger fungi with a toothed or spiny hymenium
Hymenium
The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in others some cells develop into sterile cells called cystidia or...

. As such, the family was entirely artificial, bringing together a diverse assemblage of species that have subsequently been reassigned to various families. In 1933, Dutch mycologist Marinus Anton Donk radically limited the Hydnaceae (which he referred to the tribe
Tribe (biology)
In biology, a tribe is a taxonomic rank between family and genus. It is sometimes subdivided into subtribes.Some examples include the tribes: Canini, Acalypheae, Hominini, Bombini, and Antidesmeae.-See also:* Biological classification* Rank...

 Hydneae) to Hydnum repandum and related species that produced "stichic" basidia (basidia with nuclear spindles arranged longitudinally). He considered this feature placed these species closer to the chanterelles (Cantharellaceae
Cantharellaceae
The Cantharellaceae are a family of fungi in the order Cantharellales. The family contains the chanterelles and related species, a group of fungi that superficially resemble agarics but have smooth, wrinkled, or gill-like hymenophores...

) than to other hydnoid fungi. Donk's disposition of the family was widely accepted and a standard 1995 text placed Hydnum and the Hydnaceae within the Cantharellales
Cantharellales
The Cantharellales are an order of fungi in the class Agaricomycetes. The order includes not only the chanterelles , but also some of the tooth fungi , clavarioid fungi , and corticioid fungi...

, though still retaining some additional genera (Amylodontia, Climacodon
Climacodon
Climacodon is a genus of fungi in the family Phanerochaetaceae. The widespread genus contains six species....

, Corallofungus
Corallofungus
Corallofungus is a genus of fungi in the Hydnaceae family. The genus is monotypic, containing the single species Corallofungus hatakeyamanus, found in Japan....

, Dentinum, Gloeomucro
Gloeomucro
Gloeomucro is a genus of fungi in the Hydnaceae family. The widespread genus contains nine species....

, Nigrohydnum, Phaeoradulum, and Stegiacantha
Stegiacantha
Stegiacantha is a genus of fungi in the family Meruliaceae. This is a monotypic genus, containing the single species Stegiacantha petaloides.-External links:* at Index Fungorum...

) within the family. Most of these have now been placed elsewhere.

Current status

Molecular research, based on cladistic analysis of DNA sequences, has confirmed Donk's placement of the Hydnaceae as a family within the Cantharellales. The precise boundaries of the family have not been investigated, but it appears that the type
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 and related species of the genus Sistotrema
Sistotrema
Sistotrema is a genus of fungi in the Hydnaceae family. The widespread genus contains 46 species. Phylogenetic analyses show that Sistotrema is a polyphyletic genus.-Species:*Sistotrema adnatum*Sistotrema alboluteum...

belong within the Hydnaceae, as well as most species of Hydnum itself. These Sistotrema species have poroid
Polypore
Polypores are a group of tough, leathery poroid mushrooms similar to boletes, but typically lacking a distinct stalk. The technical distinction between the two types of mushrooms is that polypores do not have the spore-bearing tissue continuous along the entire underside of the mushroom. Many...

 basidiocarps and are not closely related to the majority of "Sistotrema" species which may belong within the Clavulinaceae
Clavulinaceae
The Clavulinaceae are a family of fungi in the order Cantharellales. The family is not well defined, but currently comprises species of clavarioid fungi as well as some corticioid fungi...

. The status of Corallofungus has not been investigated. According to the Dictionary of the Fungi (10th edition, 2008), the family contains 9 genera and 190 species.

Description

The fruit bodies
Basidiocarp
In fungi, a basidiocarp, basidiome or basidioma , is the sporocarp of a basidiomycete, the multicellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do not produce such structures...

 of species in the family have caps
Pileus (mycology)
The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...

 and stems
Stipe (mycology)
thumb|150px|right|Diagram of a [[basidiomycete]] stipe with an [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...

 that are usually centrally attached. Colors typically range from white to yellow to orange, and the teeth are typically lighter than the cap surface. The flesh
Trama (mycology)
In mycology trama is a term for the inner, fleshy portion of a mushroom's basidiocarp, or fruit body. It is distinct from the outer layer of tissue, known as the pileipellis or cuticle, and from the spore-bearing tissue layer known as the hymenium....

 is fleshy and brittle, and monomitic (consisting of generative hypha
Hypha
A 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...

e only). The generative hyphae are thin-walled, branched, contain septa
Septum
In anatomy, a septum is a wall, dividing a cavity or structure into smaller ones.-In human anatomy:...

, and have clamp connection
Clamp connection
A clamp connection is a structure formed by growing hyphal cells of certain fungi. It is created to ensure each septum, or segment of hypha separated by crossed walls, receives a set of differing nuclei, which are obtained through mating of hyphae of differing sexual types...

s. Spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...

s range in shape from roughly spherical to egg-shaped, have a smooth surface, and are colorless. A distinctive characteristic of many species in the family is the structure of the hymenium
Hymenium
The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in others some cells develop into sterile cells called cystidia or...

 (spore-bearing surface), which consists of pendant, toothlike spines.

Habitat and distribution

All species within the Hydnaceae are believed to be ectomycorrhizal, forming a mutually beneficial
Mutualism
Mutualism is the way two organisms of different species biologically interact in a relationship in which each individual derives a fitness benefit . Similar interactions within a species are known as co-operation...

 relationships with the roots of living trees and other plants. Basidiocarps typically occur on the ground or in leaf litter in woodland. The family has a cosmopolitan distribution
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...

.

Economic importance

Several species of Hydnum are edible
Edible mushroom
Edible mushrooms are the fleshy and edible fruiting bodies of several species of fungi. Mushrooms belong to the macrofungi, because their fruiting structures are large enough to be seen with the naked eye. They can appear either below ground or above ground where they may be picked by hand...

 and Hydnum repandum is commercially collected and marketed in Europe, often under the French name "pied de mouton". In North America, the related Hydnum umbilicatum is also commercially collected, sometimes under the name "sweet tooth".
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