Secotioid fungi are an intermediate growth form between mushroom-like

hymenomycete Hymenomycetes was formerly the largest taxonomic group of fungi within the division Basidiomycota, but the term is no longer taxonomically relevant. Many familiar fungi belong to this class, including bracket fungi and toadstools. This class con ...

s and closed bag-shaped

gasteromycetes The gasteroid fungi are a group of fungi in the Basidiomycota. Species were formerly placed in the obsolete class Gasteromycetes Fr. (literally "stomach fungi"), or the equally obsolete order Gasteromycetales Rea, because they produce spores insi ...

, where an evolutionary process of gasteromycetation has started but not run to completion. Secotioid fungi may or may not have opening caps, but in any case they often lack the vertical

geotropic Gravitropism (also known as geotropism) is a coordinated process of differential growth by a plant in response to gravity pulling on it. It also occurs in fungi. Gravity can be either "artificial gravity" or natural gravity. It is a general featu ...

orientation of the

hymenophore A hymenophore refers to the hymenium-bearing structure of a fungal fruiting body. Hymenophores can be smooth surfaces, lamellae, folds, tubes, or teeth. The term was coined by Robert Hooke Robert Hooke FRS (; 18 July 16353 March 1703) was ...

needed to allow the spores to be dispersed by wind, and the

basidiospores A basidiospore is a reproductive spore produced by Basidiomycete fungi, a grouping that includes mushrooms, shelf fungi, rusts, and smuts. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are pro ...

are not forcibly discharged or otherwise prevented from being dispersed (e.g. gills completely inclosed and never exposed as in the secotioid form of ''

Lentinus tigrinus ''Lentinus tigrinus'' is a mushroom in the Polyporaceae The Polyporaceae are a family of poroid fungi belonging to the Basidiomycota. The flesh of their fruit bodies varies from soft (as in the case of the dryad's saddle illustrated) to v ...

'')—note—some mycologists do not consider a species to be secotioid unless it has lost ballistospory.

Explanation of secotioid development and gasteromycetation

Historically

agarics An agaric () is a type of fungus fruiting body characterized by the presence of a pileus (cap) that is clearly differentiated from the stipe (stalk), with lamellae (gills) on the underside of the pileus. In the UK, agarics are called "mushrooms ...

and

boletes {{refimprove, date=July 2020 A bolete is a type of mushroom, or fungal fruiting body. It can be identified thanks to a unique mushroom cap. The cap is clearly different from the stem. On the underside of the cap there is usually a spongy surfa ...

(which bear their spores on a

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 ...

of gills or tubes respectively) were classified quite separately from the

gasteroid fungi The gasteroid fungi are a group of fungi in the Basidiomycota. Species were formerly placed in the obsolete class Gasteromycetes Fr. (literally "stomach fungi"), or the equally obsolete order Gasteromycetales Rea, because they produce spores insi ...

, such as

puff-balls Puffballs are a type of fungus featuring a ball-shaped fruit body that bursts on impact, releasing a cloud of dust-like spores when mature. Puffballs belong to the division Basidiomycota and encompass several genera, including ''Calvatia'', ''C ...

and

truffles A truffle is the fruiting body of a subterranean ascomycete fungus, predominantly one of the many species of the genus ''Tuber''. In addition to ''Tuber'', many other genera of fungi are classified as truffles including ''Geopora'', ''Peziza ...

, of which the spores are formed in a large mass enclosed in an outer skin. However, in spite of this apparently very great difference in form, recent mycological research, both at microscopic and molecular level has shown that sometimes species of open mushrooms are much more closely related to particular species of gasteroid fungi than they are to each other. Fungi which do not open up to let their spores be dispersed in the air, but which show a clear morphological relation to agarics or boletes, constitute an intermediate form and are called secotioid. The word is derived from the name of the genus ''

Secotium ''Secotium'' is a genus of fungi in the family Agaricaceae. The members of this genus are closely related to ordinary ''Agaricus'' mushrooms, but do not open out in the usual way; this has given rise to the term "secotioid" for such mushrooms in ...

'', which was defined in 1840 by Kunze for a South African example, ''S. gueinzii'', which is the type species. In the following years numerous secotioid species were added to this genus, including ones which according to modern taxonomy belong to other genera or families. On a microscopic scale, secotioid fungi do not expel their spores forcibly from the basidium; their spores are "statismospores". Like gasteroid fungi, secotioid species rely on animals such as rodents or insects to distribute their spores. It can at times be disadvantageous for a mushroom to open up and free its spores in the usual way. If this development is aborted, a secotioid form arises, perhaps to be followed eventually by an evolutionary progression to a fully gasteroid form. This type of progression is called gasteromycetation and seems to have happened several times independently starting from various genera of "normal" mushrooms. This means that the secotioid and also the gasteroid fungi are

polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of converg ...

. According to the paper by Thiers, in certain climates and certain seasons, it may be an advantage to remain closed, because moisture can be conserved in that way. Brockhaus and Efron Encyclopedic Dictionary b11 168-5

Brockhaus and Efron Encyclopedic Dictionary b11 168-5

For example, the gasteroid genus '' Hymenogaster'' has been shown to be closely related to agaric genera such as ''

Hebeloma ''Hebeloma'' is a genus of fungi in the family Hymenogastraceae. Found worldwide, it contains the poison pie or fairy cakes ''(Hebeloma crustuliniforme)'' and the ghoul fungus ''( H. aminophilum)'', from Western Australia, which grows on rotting ...

'', which were formerly placed in family

Cortinariaceae The Cortinariaceae are a large family of gilled mushrooms found worldwide, containing over 2100 species. The family takes its name from its largest genus, the varied species of the genus ''Cortinarius''. Many genera formerly in the Cortinariacea ...

Strophariaceae The Strophariaceae are a family of fungi in the order Agaricales. Under an older classification, the family covered 18 genera and 1316 species. The species of Strophariaceae have red-brown to dark brown spore prints, while the spores themselves a ...

. This is found by DNA analysis and also indicated on a microscopic scale by the resemblance of the spores and basidia. According to a current classification system, ''Hebeloma'' now belongs to family

Hymenogastraceae The Hymenogastraceae is a family of fungi in the order Agaricales with both agaric and false-truffle shaped fruitbodies. Formerly, prior to molecular analyses, the family was restricted to the false-truffle genera. The mushroom genus ''Psilocybe' ...

, and is considered more narrowly related to the closed '' Hymenogaster'' fungi than, for instance, to the ordinary mushrooms in genus ''

Cortinarius ''Cortinarius'' is a globally distributed genus of mushrooms in the family Cortinariaceae. It is suspected to be the largest genus of agarics, containing over 2,000 widespread species. A common feature among all species in the genus ''Cortinari ...

''. A similar case is the well-known "Deceiver" mushroom ''

Laccaria laccata ''Laccaria laccata'', commonly known as the deceiver, or waxy laccaria, is a white-spored species of small edible mushroom found throughout North America and Europe. It is a highly variable mushroom (hence 'deceiver'), and can look quite washed o ...

'' which is now classified in the ''

Hydnangiaceae The Hydnangiaceae are a family of fungi in the mushroom order Agaricales. Widespread in temperate and tropical regions throughout the world, the family contains about 30 species in four genera. Species in the Hydnangiaceae form ectomycorrhizal re ...

'', ''Hydnangium'' being a gastroid genus. It has been found that a change in a single locus of a gene of the gilled mushroom ''

'' causes it to have a closed fruiting body. This suggests that the emergence of a secotioid species may not require many mutations. There is a spectrum of secotioid species ranging from the open form to the closed form in the following respects: *there may be an evident stipe, or there may be only a remnant consisting of a column of non-fertile tissue, *if there is a stipe the edge of the cap may separate from it (partially opening), or may not, *there may be recognizable gills (though oriented in all directions and very convoluted), or the fertile interior may be uniform like the

gleba Gleba (, from Latin ''glaeba, glēba'', "lump") is the fleshy spore-bearing inner mass of certain fungi such as the puffball or stinkhorn. The gleba is a solid mass of spores, generated within an enclosed area within the sporocarp. The continu ...

of gasteroid fungi, and *the spore-bearing tissue may be above ground (

epigeous Epigeal, epigean, epigeic and epigeous are biological terms describing an organism's activity above the soil surface. In botany, a seed is described as showing epigeal germination when the cotyledons of the germinating seed expand, throw off the ...

), or underground (

hypogeous Hypogeal, hypogean, hypogeic and hypogeous (; ) are biological terms describing an organism's activity below the soil surface. In botany, a seed is described as showing hypogeal germination when the cotyledons of the germinating seed remain non ...

), or partly buried. The adjective "sequestrate" is sometimes used as a general term to mean "either secotioid or gasteroid".

Examples

'' is a very widespread genus of agarics, but also contains some secotioid species, such as ''C. leucocephalus'', ''C. coneae'' and ''C. cartilagineus''. Pholiota nubigena (Harkn

Pholiota nubigena ''Pholiota nubigena'', commonly known as the gastroid pholiota or the bubble gum fungus, is a species of secotioid fungus in the family Strophariaceae. It is found in mountainous areas of the western United States, where it grows on rotting con ...

'' is a secotioid species found early in the year at high altitude in the western United States. It was originally assigned to ''

'' and later to a more specific secotioid genus ''Nivatogastrium'', but in fact it is closely allied to ''

Pholiota squarrosa ''Pholiota squarrosa'', commonly known as the shaggy scalycap, the shaggy Pholiota, or the scaly Pholiota, is a species of mushroom in the family Strophariaceae. Common in North America and Europe, it is often an opportunistic parasite, and ha ...

'' and it has now been moved to genus ''

Pholiota ''Pholiota'' is a genus of small to medium-sized, fleshy mushrooms in the family Strophariaceae. They are saprobes that typically live on wood. The genus has a widespread distribution, especially in temperate regions, and contains about 150 spe ...

'' itself, although the latter consists primarily of

agaric An agaric () is a type of fungus fruiting body characterized by the presence of a pileus (cap) that is clearly differentiated from the stipe (stalk), with lamellae (gills) on the underside of the pileus. In the UK, agarics are called "mushrooms ...

s. '' Gastroboletus'' is a secotioid

bolete {{refimprove, date=July 2020 A bolete is a type of mushroom, or fungal fruiting body. It can be identified thanks to a unique mushroom cap. The cap is clearly different from the stem. On the underside of the cap there is usually a spongy surfa ...

genus where the fruiting bodies may or may not open, but in any case the tubes are not aligned vertically as in a true bolete. ''

Agaricus deserticola ''Agaricus deserticola'', commonly known as the gasteroid agaricus, is a species of fungus in the family Agaricaceae. Found only in southwestern and western North America, ''A. deserticola'' is adapted for growth in dry or semi-arid habitats ...

'' is a secotioid species of ''

Agaricus ''Agaricus'' is a genus of mushrooms containing both edible and poisonous species, with over 400 members worldwide and possibly again as many disputed or newly-discovered species. The genus includes the common ("button") mushroom (''Agaricus bisp ...

'' (the genus of common cultivated mushrooms) which at one time was placed in the genus ''Secotium''. Similarly, ''

Agaricus inapertus ''Agaricus inapertus'' is a species of secotioid fungus in the genus ''Agaricus''. It was first described by American mycologists Rolf Singer and Alexander H. Smith in 1958 as ''Endoptychum depressum''. Molecular phylogenetics, Molecular analysis ...

'' was formerly known as ''Endoptychum depressum'' until

molecular A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...

analysis revealed it to be closely aligned with ''Agaricus''.

References

{{Reflist, refs= {{Cite journal , author-link = M. Binder & A. Bresinsky , title = Derivation of a polymorphic lineage of Gasteromycetes from boletoid ancestors , journal = Mycologia , volume = 94 , issue = 1 , pages = 85–98 , publisher = The New York Botanical Garden, Bronx. NY 10458 , location = New York , year = 2002 , url = http://www.mycologia.org/cgi/content/full/94/1/85 , doi=10.2307/3761848 , pmid=21156480, last1 = Binder , first1 = M , last2 = Bresinsky , first2 = A , jstor = 3761848 {{Cite journal , author-link = Henry S. Conard , title = The Structure and Development of Secotium agaricoides , journal = Mycologia , volume = 7 , issue = 2 , pages = 94–104 , publisher = The New York Botanical Garden, Bronx. NY 10458 , location = New York , date = March 1915 , url = http://www.mykoweb.com/systematics/literature/The%20Secotioid%20Syndrome.pdf , doi=10.2307/3753132, jstor = 3753132 , last1 = Conard , first1 = Henry S {{Cite journal , title = Historical and current perspectives in the systematics of Australian cortinarioid sequestrate (truffle-like) fungi. , journal = Australasian Mycologist , volume = 21 , issue = 3 , pages = 81–116 , year = 2002 , url = http://bugs.bio.usyd.edu.au/AustMycolSoc/Journal/2002/21_3_b.pdf {{Cite journal , author-link = David S. Hibbett et al. , title = Evolution of gilled mushrooms and puffballs inferred from ribosomal DNA sequences , journal = PNAS , volume = 94 , issue = 22 , pages = 12002–12006 , publisher = National Academy of Sciences of the United States of America , location = Washington DC , date = 1997-10-28 , doi=10.1073/pnas.94.22.12002 , pmid=9342352 , pmc=23683, last1 = Hibbett , first1 = D. S , last2 = Pine , first2 = E. M , last3 = Langer , first3 = E , last4 = Langer , first4 = G , last5 = Donoghue , first5 = M. J , bibcode = 1997PNAS...9412002H , doi-access = free {{cite journal , author1=Hibett DS , author2=Tsuneda A , author3=Shigeyuki M. , year= 1994 , title=The Secotioid Form of ''Lentinus tegrinus'':Genetics and Development of a Fungal Morphological Innovation. , journal=American Journal of Botany , volume=81 , issue=4 , pages=466–478 , doi=10.2307/2445497, jstor=2445497 For genus ''Secotium'', also see {{cite web , url=http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=39251 , title=the ''Secotium'' Kunze page , work=Index Fungorum , publisher=Royal Botanic Gardens Kew , accessdate=2022-06-18 {{cite journal , vauthors=Matheny PB, Curtis JM, Hofstetter V, Aime MC, Moncalvo JM, Ge ZW, Yang ZL, Slot JC, Ammirati JF, Baroni TJ, Bougher NL, Hughes KW, Lodge DJ, Kerrigan RW, Seidl MT, Aanen DK, DeNitis M, Daniele GM, Desjardin DE, Kropp BR, Norvell LL, Parker A, Vellinga EC, Vilgalys R, Hibbett DS , title=Major clades of Agaricales: a multilocus phylogenetic overview , journal=Mycologia , volume=98 , issue=6 , year=2007 , pages=982–95 , doi=10.3852/mycologia.98.6.982 , pmid=17486974, url=https://naldc-legacy.nal.usda.gov/naldc/download.xhtml?id=349&content=PDF {{open access Se
this Mykoweb page
of ''Nivatogastrium nubigenum'', which shows rudimentary lamellae. {{cite web , url=http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=550583 , title=the ''Pholiota nubigena'' page , work=Species Fungorum , publisher=Royal Botanic Gardens Kew , access-date=2020-05-24 To see which species of ''Secotium'' have been assigned to a new (presumably more appropriate) genus and which remain under that taxon, see {{cite web , url=https://www.speciesfungorum.org/Names/Names.asp , title=the Species Fungorum search page , work=Species Fungorum , publisher=Royal Botanic Gardens Kew , accessdate=2022-06-18 Then select "genus" and search for ''Secotium''. The following 1984 article provides a good introduction to sectioid fungi: {{Cite journal , author-link = Harry D. Thiers , title = The Secotioid Syndrome , journal = Mycologia , volume = 76 , issue = 1 , pages = 1–8 , publisher = The New York Botanical Garden, Bronx. NY 10458 , location = New York , date = January–February 1984 , url = http://www.mykoweb.com/systematics/literature/The%20Secotioid%20Syndrome.pdf , doi=10.2307/3792830, jstor = 3792830 , last1 = Thiers , first1 = Harry D {{cite journal , author1=Vellinga EC , author2=de Kok RPJ , author3=Bruns TD. , title=Phylogeny and taxonomy of ''Macrolepiota'' (Agaricaceae) , journal=Mycologia , year=2003 , volume=95 , issue=3 , pages=442–56 , url=http://www.cybertruffle.org.uk/cyberliber/59350/0095/003/0442.htm , doi=10.2307/3761886 , pmid=21156633, jstor=3761886 Mycology Fungal morphology and anatomy Mushroom types