Species of fungus
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Hexagonia hydnoides, also known as the hairy hexagonia, is a widely distributed species of bracket fungus in the Polyporaceae family. The name comes from the species' distinctive dark hairy bristles found on the cap - "hydnoides" meaning 'relating to "Hydnum",' a genus of toothed fungi. In general, it is known to grow in tropical regions across the globe and to grow on dead wood tissues, particularly that of hardwoods. It is a plant pathogen. This fungus is largely saprophytic, decaying dead wood tissues.
Description.
Morphology.
"Hexagonia hydnoides" forms annual semicircular fruiting bodies, with a sessile, or stalkless, attachment to dead wood, such as that of a fallen oak. The pileus, or cap, is convex or nearly flat and has been reported to be anywhere from 1 to 2.5 centimeters in length all the way up to 5 to 10 centimeters in length, and can be up to 1.5 centimeters thick but is often much less. The upper surface is zonate - having concentric striping patterns that can be faint to bright in coloration, and is otherwise brown or dark brown. The cap is distinctively covered in fine, dark brown to black bristles that dry and harden with age. The hymenium is brown to dark brown, and is composed of many thin, angular or hexagonal pores – 0.1 to 0.2 mm in diameter and running 2 to 6 mm deep. The hymenium of fresh specimens will bruise brown when damaged.
The microscopic morphology of this species includes spores that are 11–14 by 3.5-5 microns, which are cylindrical, smooth, hyaline/colorless, and inamyloid under Melzer's reagent. The hyphal system is trimitic, meaning that it contains generative, skeletal, and binding hyphae, and in addition has clamp connections present on the binding hyphae.
Similar species.
Many species that can be confused with "Hexagonia hydnoides" include bracket fungi which lack a stipe – examples may be "Trametes versicolor" (the turkey-tail) along with other "Trametes" species, "Fuscoporia gilva", or "Daedaleopsis confragosa". "Hexagonia hydnoides" can sometimes be differentiated from lookalikes within the genus, notably "Hexagonia hirta", by its much smaller pores and flat or slightly convex cap surface as described above.
Ecology.
"Hexagonia hydnoides" is saprobic, most commonly decaying fallen hardwood trees. It is a white-rot fungus, meaning that it secretes enzymes that can break down components of the wood including cellulose, hemicellulose, and lignin, the latter of which is not digestible by some wood-decay fungi. This fungus is also known to be a plant pathogen, decaying living wood, although this has not been researched in depth.
Distribution.
The fungus can largely be found in tropical &amp; subtropical forests, especially those in North America. Geographic data from iNaturalist shows that it has been sighted in the eastern United States, Mexico, Caribbean, Brazil, Spain, India, South Africa along with much of Central and South America and some Southern and East African countries.
Taxonomy.
"Hexagonia hydnoides" was placed within "Boletus" in its original description by Carl Linnaeus in 1753, along with most other fungi with poroid hymenia. The most recent widely accepted placement for the species is within "Hexagonia".
It is disputed among researchers whether this species falls within the genus "Cerrena" or within the genus "Hexagonia". A study published in 2001 reassigned this species to "Cerrena", under the name "Cerrena hydnoides"". " Species Fungorum lists "Cerrena hydnoides" as the currently accepted name for this species, but this is not reflected in all of the modern literature.
Phylogeny.
In a phylogenetic study done in 2013 on various genera within the order "Polyporales", it was shown that "Hexagonia hydnoides" is a sister lineage to "Irpex lacteus" and "Emmia latemarginata". Further investigation within this study argued that "Hexagonia hydnoides" is microscopically distinct from other members of its genus ("Hexagonia hirta", "Hexagonia apiaria") due to an arboriform (tree-like) branching pattern and sclerohyphae with inflated axial elements – and suggested the species be moved to "Pogonomyces""."
Traditional medicine.
Although "Hexagonia hydnoides" is considered inedible due to its tough, woody texture, therapeutic compounds within the basidiocarp can be extracted for use in traditional herbal medicines such as teas through being ground into a powder.
A study published in 2021 analyzed the common knowledge, usage, and effects of various fungi in traditional medicine in rural Northeastern Brazilian communities. "H. hydnoides" was specifically cited for use as a solution to colic in infants, as an antispasmodic therapy for the digestive system. "H. hydnoides" was further analyzed and found to have antibacterial properties as a result of saponin compounds. A similar study found that extracts from "H. hydnoides" were effective as an antibacterial agent against "Bacillus cereus".
The usage of "H. hydnoides" in traditional medicine is endangered by increased access to commercially produced medicines, loss of tradition throughout generations, and a decline in fungal species populations due to environmental factors such as deforestation, which is particularly relevant to "Hexagonia hydnoides"' use among populations in South America, especially regarding the gradual loss of Brazilian rainforests"."
The fungus is also reported to be used in Mexico as a medicine for the treatment of pimples, warts, and ringworm.
References.
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