''Tremella'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

fungi A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...

in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Tremellaceae. All ''Tremella'' species are

parasites Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

of other fungi and most produce

anamorph In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the Biological life cycle, life cycles of fungi in the Phylum, phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a Asc ...

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to consti ...

states.

Basidiocarps 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 ...

(fruit bodies), when produced, are gelatinous and are colloquially classed among the "

jelly fungi Jelly fungi are a paraphyletic group of several heterobasidiomycete fungal orders from different classes of the subphylum Agaricomycotina: Tremellales, Dacrymycetales, Auriculariales and Sebacinales. These fungi are so named because their ...

". Over 100 species of ''Tremella'' (in its wide sense) are currently recognized worldwide. One species, ''

Tremella fuciformis ''Tremella fuciformis'' is a species of fungus; it produces white, frond-like, gelatinous basidiocarps (fruiting bodies). It is widespread, especially in the tropics, where it can be found on the dead branches of broadleaf trees. This fungus is c ...

'', is commercially cultivated for food.

Taxonomy

History

''Tremella'' was one of the original genera created by

Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, t ...

in his ''

Species Plantarum ' (Latin for "The Species of Plants") is a book by Carl Linnaeus, originally published in 1753, which lists every species of plant known at the time, classified into genera. It is the first work to consistently apply binomial names and was the ...

'' of 1753. The name comes from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

''tremere'' meaning "to tremble". Linnaeus placed ''Tremella'' in the

algae Algae ( , ; : alga ) are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from ...

, including within it a variety of gelatinous growths, including

seaweeds Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of ''Rhodophyta'' (red), '' Phaeophyta'' (brown) and '' Chlorophyta'' (green) macroalgae. Seaweed species such a ...

, cyanobacteria, and myxomycetes, as well as fungi. Subsequent authors added additional species to this mix, until

Persoon Christiaan Hendrik Persoon (1 February 1761 – 16 November 1836) was a German mycologist who made additions to Linnaeus' mushroom taxonomy. Early life Persoon was born in South Africa at the Cape of Good Hope, the third child of an immig ...

revised ''Tremella'' in 1794 and 1801, repositioning the genus within the fungi. Persoon's reinterpretation of ''Tremella'' was sufficiently radical to be considered a separate genus (''Tremella'' Pers.) from that originally created by Linnaeus (''Tremella'' L.). Tremella Pers. has now been conserved under the

International Code of Nomenclature for algae, fungi, and plants The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "trad ...

, with '' Tremella mesenterica'' as the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

Current status

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 bioch ...

research, based on

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived ch ...

analysis of

DNA sequences A nucleic acid sequence is a succession of bases signified by a series of a set of five different letters that indicate the order of nucleotides forming alleles within a DNA (using GACT) or RNA (GACU) molecule. By convention, sequences are usu ...

, has shown that ''Tremella'' (as previously understood) is

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 conver ...

(and hence artificial), with most species not closely related to the

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * Ty ...

. Accordingly, some species have been transferred to new genera and new families: ''Tremella foliacea'' and related species are now placed in the genus '' Phaeotremella'' within the family Phaeotremellaceae; ''Tremella encephala'' and related species are now placed in the genus '' Naematelia'' within the Naemateliaceae; ''Tremella moriformis'' and related species are now placed in the genus '' Pseudotremella'' within the Bulleraceae; and ''Tremella polyporina'' is now placed in the genus '' Carcinomyces'' within the Carcinomycetaceae. Several other species groups have not yet been renamed, pending further research. More than 500 species have been described in ''Tremella'', but most of these are old names of doubtful application or old names for species later transferred to other genera. In its strict sense, the genus ''Tremella'' now contains some 30-40 species, including the type '' Tremella mesenterica'' and the cultivated species '' T. fuciformis''.

Description

Fruit bodies (when present) are gelatinous. In some species they are small (under 5 mm across) and pustular to pulvinate (cushion-shaped). In others they are much larger (up to 150 mm across) and may be variously lobed, cephaliform (like a brain, with folds and ridges), or foliose (with leaf-like or seaweed-like fronds). Many ''Tremella'' species, however, are hymenial parasites, producing spores within the fruit bodies of their hosts, and are only visible microscopically.

Microscopic characters

''Tremella'' species produce

hyphae A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one or ...

that are typically (but not always) clamped and have haustorial cells from which hyphal filaments seek out and penetrate the hyphae of the host. The

basidia A basidium () is a microscopic sporangium (a spore-producing structure) found on the hymenophore of fruiting bodies of basidiomycete fungi which are also called tertiary mycelium, developed from secondary mycelium. Tertiary mycelium is highly- ...

are "tremelloid" (globose to ellipsoid, sometimes stalked, and vertically or diagonally septate), giving rise to long, sinuous

sterigmata In biology, a sterigma (pl. sterigmata) is a small supporting structure. It commonly refers to an extension of the basidium (the spore-bearing cells) consisting of a basal filamentous part and a slender projection which carries a spore at the ti ...

or epibasidia on which 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 ...

are produced. These spores are smooth, globose to ellipsoid, and germinate by hyphal tube or by

cells. Conidiophores are often present, producing

conidiospores A conidium ( ; ), sometimes termed an asexual chlamydospore or chlamydoconidium (), is an asexual, non-motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also called mitospores due to th ...

that are similar to yeast cells.

Habitat and distribution

Species are mainly parasitic on wood-rotting fungi in the phyla

Ascomycota Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The de ...

and

Basidiomycota Basidiomycota () is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basi ...

, particularly on species that occur on dead attached branches. Hosts include members of the

corticioid fungi The corticioid fungi are a group of fungi in the Basidiomycota typically having effused, smooth basidiocarps (fruit bodies) that are formed on the undersides of dead tree trunks or branches. They are sometimes colloquially called crust fungi or pa ...

and

Dacrymycetales The Dacrymycetes are a class of fungi in the Basidiomycota. The class currently contains the single order Dacrymycetales, with a second proposed order Unilacrymales now treated at the family level. The order contains four families and has a cos ...

in the Basidiomycota and species of '' Diaporthe'', other

Sordariomycetes Sordariomycetes is a class of fungi in the subdivision Pezizomycotina (Ascomycota), consisting of 28 orders, 90 families, 1344 genera. Sordariomycetes is from the Latin sordes (filth) because some species grow in animal feces, though growth habit ...

, and

lichens A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.Tremellomycetes