Secotioid

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Psilocybe weraroa, a secotioid form of the bluing Psilocybe in the cyanescens complex. Weraroa novae zelandiae.jpg
Psilocybe weraroa , a secotioid form of the bluing Psilocybe in the cyanescens complex.

Secotioid fungi are an intermediate growth form between mushroom-like hymenomycetes and closed bag-shaped gasteromycetes, 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 orientation of the hymenophore needed to allow the spores to be dispersed by wind, and the basidiospores 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 )—note—some mycologists do not consider a species to be secotioid unless it has lost ballistospory. [1]

Contents

Explanation of secotioid development and gasteromycetation

Historically agarics and boletes (which bear their spores on a hymenium of gills or tubes respectively) were classified quite separately from the gasteroid fungi, such as puff-balls and truffles, 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 [2] and molecular [3] 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. [2]

The word is derived from the name of the genus Secotium , 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. [4] [5] [6]

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. According to the paper by Thiers, [2] in certain climates and certain seasons, it may be an advantage to remain closed, because moisture can be conserved in that way.

Cross-section of Hymenogaster tener Brockhaus and Efron Encyclopedic Dictionary b11 168-5.jpg
Cross-section of Hymenogaster tener

For example, the gasteroid genus Hymenogaster has been shown to be closely related to agaric genera such as Hebeloma , which were formerly placed in family Cortinariaceae or Strophariaceae. 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, and is considered more narrowly related to the closed Hymenogaster fungi than, for instance, to the ordinary mushrooms in genus Cortinarius . [7] [8]

A similar case is the well-known "Deceiver" mushroom Laccaria laccata which is now classified in the Hydnangiaceae , Hydnangium being a gastroid genus.

It has been found that a change in a single locus of a gene of the gilled mushroom Lentinus tigrinus causes it to have a closed fruiting body. This suggests that the emergence of a secotioid species may not require many mutations. [3]

There is a spectrum of secotioid species ranging from the open form to the closed form in the following respects:

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

Examples

Cortinarius is a very widespread genus of agarics, but also contains some secotioid species, such as C. leucocephalus, C. coneae and C. cartilagineus.

Pholiota nubigena Pholiota nubigena (Harkn.) Redhead 352483.jpg
Pholiota nubigena

Pholiota nubigena is a secotioid species found early in the year at high altitude in the western United States. It was originally assigned to Secotium and later to a more specific secotioid genus Nivatogastrium, but in fact it is closely allied to Pholiota squarrosa [2] and it has now been moved to genus Pholiota itself, although the latter consists primarily of agarics. [9] [10] [11]

Gastroboletus is a secotioid bolete 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. [2]

Agaricus deserticola Agaricus deserticola G. Moreno, Esqueda & Lizarraga 762174.jpg
Agaricus deserticola

Agaricus deserticola is a secotioid species of Agaricus (the genus of common cultivated mushrooms) which at one time was placed in the genus Secotium. Similarly, Agaricus inapertus was formerly known as Endoptychum depressum until molecular analysis revealed it to be closely aligned with Agaricus. [12]

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The fungal order Agaricales, also known as gilled mushrooms or euagarics, contains some of the most familiar types of mushrooms. The order has 33 extant families, 413 genera, and over 13,000 described species, along with six extinct genera known only from the fossil record. They range from the ubiquitous common mushroom to the deadly destroying angel and the hallucinogenic fly agaric to the bioluminescent jack-o-lantern mushroom.

<i>Agaricus bisporus</i> Species of fungus

Agaricus bisporus is an edible basidiomycete mushroom native to grasslands in Eurasia and North America. It has two color states while immature – white and brown – both of which have various names, with additional names for the mature state.

<i>Lepiota</i> Genus of fungi

Lepiota is a genus of gilled mushrooms in the family Agaricaceae. All Lepiota species are ground-dwelling saprotrophs with a preference for rich, calcareous soils. Basidiocarps are agaricoid with whitish spores, typically with scaly caps and a ring on the stipe. Around 400 species of Lepiota are currently recognized worldwide. Many species are poisonous, some lethally so.

<span class="mw-page-title-main">Agaricaceae</span> Family of fungi

The Agaricaceae are a family of basidiomycete fungi and include the genus Agaricus, as well as basidiomycetes previously classified in the families Tulostomataceae, Lepiotaceae, and Lycoperdaceae.

<span class="mw-page-title-main">Russulaceae</span> Family of fungi in the order Russulales

The Russulaceae are a diverse family of fungi in the order Russulales, with roughly 1,900 known species and a worldwide distribution. They comprise the brittlegills and the milk-caps, well-known mushroom-forming fungi that include some edible species. These gilled mushrooms are characterised by the brittle flesh of their fruitbodies.

<span class="mw-page-title-main">Strophariaceae</span> Family of fungi

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 are smooth and have an apical germ pore. These agarics are also characterized by having a cutis-type pileipellis. Ecologically, all species in this group are saprotrophs, growing on various kinds of decaying organic matter. The family was circumscribed in 1946 by mycologists Rolf Singer and Alexander H. Smith.

<span class="mw-page-title-main">Partial veil</span> Mushroom anatomy

In mycology, a partial veil is a temporary structure of tissue found on the fruiting bodies of some basidiomycete fungi, typically agarics. Its role is to isolate and protect the developing spore-producing surface, represented by gills or tubes, found on the lower surface of the cap. A partial veil, in contrast to a universal veil, extends from the stem surface to the cap edge. The partial veil later disintegrates, once the fruiting body has matured and the spores are ready for dispersal. It might then give rise to a stem ring, or fragments attached to the stem or cap edge. In some mushrooms, both a partial veil and a universal veil may be present.

<i>Pleurotus</i> Genus of fungi

Pleurotus is a genus of gilled mushrooms which includes one of the most widely eaten mushrooms, P. ostreatus. Species of Pleurotus may be called oyster, abalone, or tree mushrooms, and are some of the most commonly cultivated edible mushrooms in the world. Pleurotus fungi have also been used in mycoremediation of pollutants, such as petroleum and polycyclic aromatic hydrocarbons.

<i>Gomphidius</i> Genus of mushrooms

Gomphidius is a genus of mushrooms, commonly known as spike-caps, that are members of the Boletales, or pored fungi. They appear to have gill-like structures which resemble those of agarics, however the similarity is superficial only. The best-known member is the slimy spike-cap. The genus has a widespread distribution, especially in north temperate areas, and contains 10 species.

<span class="mw-page-title-main">Entolomataceae</span> Family of fungi

The Entolomataceae, also known as Rhodophyllaceae, are a large family of pink-spored terrestrial gilled mushrooms which includes the genera Entoloma, Rhodocybe, and Clitopilus. The family collectively contains over 1500 species, the large majority of which are in Entoloma. Genera formerly known as Leptonia and Nolanea, amongst others, have been subsumed into Entoloma. Mushrooms in the Entolomataceae typically grow in woodlands or grassy areas and have attached gills, differentiating them from the Pluteaceae, which have free gills.

<span class="mw-page-title-main">Alexander H. Smith</span> American mycologist (1904-1986)

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<i>Panus conchatus</i> Species of fungus

Panus conchatus, commonly known as the lilac oysterling, is an inedible species of mushroom that occurs throughout the Northern Hemisphere. Its fruitbodies are characterized by a smooth, lilac- or tan-colored cap, and decurrent gills. The fungus is saprophytic and fruits on the decomposing wood of a wide variety of deciduous and coniferous trees. Despite being a gilled species, phylogenetic analysis has shown it is closely related to the pored species found in the family Polyporaceae.

Endoptychum is a genus of secotioid fungi in the family Agaricaceae. Like the majority of secotioid taxa, the individual species of Endoptychum are thought to be recent mutations from agaricoid species, hence, Endoptychum is likely not a valid monophyletic genus.

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 general. They are thought to form an evolutionary link between agarics and gasteroid fungi. Secotium is a widespread genus, with species that are predominantly found in warm and arid regions.

<i>Pholiota flammans</i> Species of fungus

Pholiota flammans, commonly known as the yellow pholiota, the flaming Pholiota, or the flame scalecap, is a basidiomycete agaric mushroom of the genus Pholiota. Its fruit body is golden-yellow in color throughout, while its cap and stem are covered in sharp scales. As it is a saprobic fungus, the fruit bodies typically appear in clusters on the stumps of dead coniferous trees. P. flammans is distributed throughout Europe, North America, and Asia in boreal and temperate regions. Its edibility has not been clarified.

<i>Agaricus deserticola</i> Species of fungus in the family Agaricaceae endemic to southwestern and western North America

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. The fruit bodies are secotioid, meaning the spores are not forcibly discharged, and the cap does not fully expand. Unlike other Agaricus species, A. deserticola does not develop true gills, but rather a convoluted and networked system of spore-producing tissue called a gleba. When the partial veil breaks or pulls away from the stem or the cap splits radially, the blackish-brown gleba is exposed, which allows the spores to be dispersed.

<span class="mw-page-title-main">Gasteroid fungi</span> Group of fungi

The gasteroid fungi are a group of fungi in the Basidiomycota. Species were formerly placed in the obsolete class Gasteromycetes Fr., or the equally obsolete order Gasteromycetales Rea, because they produce spores inside their basidiocarps rather than on an outer surface. However, the class is polyphyletic, as such species—which include puffballs, earthstars, stinkhorns, and false truffles—are not closely related to each other. Because they are often studied as a group, it has been convenient to retain the informal (non-taxonomic) name of "gasteroid fungi".

<i>Pholiota squarrosa</i> Species of fungus

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 has a wide range of hosts among deciduous trees, although it can also infect conifers. It can also live as a saprobe, deriving nutrients from decomposing wood. The mushroom is typically found growing in clusters at the base of trees and stumps. Both the cap and the stem are covered in small, pointed scales that are pointed downward and backward. The crowded gills are yellowish, then later rust-brown. The mushroom has an odor that, depending on the author, has been described as resembling garlic, lemon, radish, onion, or skunk. It has a strong taste, resembling radishes. Though edible to some, it may be toxic, especially if consumed in combination with alcohol. The mushroom contains unique chemicals thought to help it infect plants by neutralizing defensive responses employed by them. The very similar P. squarrosoides differs in having a paler cap that is sticky between the scales, and smaller spores.

<i>Montagnea arenaria</i> Species of fungus

Montagnea arenaria is a species of secotioid fungus in the family Agaricaceae. Originally named Agaricus arenarius by Augustin Pyramus de Candolle in 1815, it was transferred to the genus Montagnea by Sanford Myron Zeller in 1943. The species is characterized by a cap that has an apical disc, radial gills, a hymenophore, and spores with a prominent germ pore. It is inedible.

<i>Pholiota nubigena</i> Species of fungus

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 conifer wood, often fir logs. It fruits in spring, often under snow, and early summer toward the end of the snowmelt period in high mountain forests. Fruit bodies appear similar to unopened mushrooms, measuring 1–4 centimetres tall with 1–2.4 cm diameter caps that are whitish to brownish. They have a short but distinct whitish stipe that extend through the internal spore mass (gleba) of the fruit body into the cap. The gleba consists of irregular chambers made of contorted gills that are brownish in color. A whitish, cottony partial veil is present in young specimens, but it often disappears in age and does not leave a ring on the stipe.

References

  1. Hibett DS; Tsuneda A; Shigeyuki M. (1994). "The Secotioid Form of Lentinus tegrinus:Genetics and Development of a Fungal Morphological Innovation". American Journal of Botany. 81 (4): 466–478. doi:10.2307/2445497. JSTOR   2445497.
  2. 1 2 3 4 5 The following 1984 article provides a good introduction to sectioid fungi: Thiers, Harry D (January–February 1984). "The Secotioid Syndrome" (PDF). Mycologia. New York: The New York Botanical Garden, Bronx. NY 10458. 76 (1): 1–8. doi:10.2307/3792830. JSTOR   3792830.
  3. 1 2 Hibbett, D. S; Pine, E. M; Langer, E; Langer, G; Donoghue, M. J (1997-10-28). "Evolution of gilled mushrooms and puffballs inferred from ribosomal DNA sequences". PNAS. Washington DC: National Academy of Sciences of the United States of America. 94 (22): 12002–12006. Bibcode:1997PNAS...9412002H. doi: 10.1073/pnas.94.22.12002 . PMC   23683 . PMID   9342352.
  4. Conard, Henry S (March 1915). "The Structure and Development of Secotium agaricoides" (PDF). Mycologia. New York: The New York Botanical Garden, Bronx. NY 10458. 7 (2): 94–104. doi:10.2307/3753132. JSTOR   3753132.
  5. To see which species of Secotium have been assigned to a new (presumably more appropriate) genus and which remain under that taxon, see "the Species Fungorum search page". Species Fungorum. Royal Botanic Gardens Kew. Retrieved 2022-06-18. Then select "genus" and search for Secotium.
  6. For genus Secotium, also see "the Secotium Kunze page". Index Fungorum. Royal Botanic Gardens Kew. Retrieved 2022-06-18.
  7. Binder, M; Bresinsky, A (2002). "Derivation of a polymorphic lineage of Gasteromycetes from boletoid ancestors". Mycologia. New York: The New York Botanical Garden, Bronx. NY 10458. 94 (1): 85–98. doi:10.2307/3761848. JSTOR   3761848. PMID   21156480.
  8. "Historical and current perspectives in the systematics of Australian cortinarioid sequestrate (truffle-like) fungi" (PDF). Australasian Mycologist. 21 (3): 81–116. 2002.
  9. See this Mykoweb page of Nivatogastrium nubigenum, which shows rudimentary lamellae.
  10. 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 (2007). "Major clades of Agaricales: a multilocus phylogenetic overview". Mycologia. 98 (6): 982–95. doi:10.3852/mycologia.98.6.982. PMID   17486974. Open Access logo PLoS transparent.svg
  11. "the Pholiota nubigena page". Species Fungorum. Royal Botanic Gardens Kew. Retrieved 2020-05-24.
  12. Vellinga EC; de Kok RPJ; Bruns TD. (2003). "Phylogeny and taxonomy of Macrolepiota (Agaricaceae)". Mycologia. 95 (3): 442–56. doi:10.2307/3761886. JSTOR   3761886. PMID   21156633.