Helotiales
Helotiales is an order (biology), order of the class Leotiomycetes within the division Ascomycota. The taxonomy within Helotiales has been debated. It has expanded significantly as genomic techniques for taxonomical identification have become mor ...
, but not yet assigned to a family. The two species in this genus produce minute, hairy, disc-shaped
fruiting bodies
The sporocarp (also known as fruiting body, fruit body or fruitbody) of fungi is a multicellular structure on which spore-producing structures, such as basidia or asci, are borne. The fruitbody is part of the sexual phase of a fungal life cyc ...
on the surface of their lichen
hosts
A host is a person responsible for guests at an event or for providing hospitality during it.
Host may also refer to:
Places
* Host, Pennsylvania, a village in Berks County
* Host Island, in the Wilhelm Archipelago, Antarctica
People
* ...
. They are distinguished from similar fungi by their characteristic violet pigment, which changes to blue-grey or reddish-orange when treated with different chemical solutions.
Taxonomy
The species now called ''Neoechinodiscus lesdainii'' was first described as ''Phacopsis lesdainii'' by
Léon Vouaux
Léon Vouaux (1870 – 1914) was a French priest, philologist and lichenologist. He was executed by German forces in the second month of the First World War. The Académie Française awarded him the Prix Saintour posthumously in 1915.
Early li ...
in 1914. When Javier Etayo and Paul Diederich re-examined fresh collections in the 1990s, they found that its minuscule, hairy
apothecia
An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. As ...
(fruiting bodies), the striking violet pigment that turns blue-grey in K and reddish-orange in nitric acid, and the thin-walled, iodine-negative asci could not be reconciled with '' Phacopsis'', '' Skyttea'' or any other known lichenicolous genus. They therefore erected the monotypic genus ''Echinodiscus'' in 2000 and, because Bouly de Lesdain's
holotype
A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
had been destroyed during the Second World War, chose a Coppins specimen from
Castle Coole
Castle Coole (from Logainm – Castle Coole – scanned record 2) is a
neotype
In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to anchor or centralizes ...
. The generic name alluded to the "spiny" look of the hairy discs, and the authors placed the taxon in the order then called Leotiales (now Helotiales) but left it unassigned to family because no close relatives were apparent.
A second species, ''Echinodiscus kozhevnikovii'', was added from the
Russian Arctic
The Extreme North or the Far North is a large part of Russia located mainly north of the Arctic Circle and boasting enormous mineral and natural resources. Its total area is about , comprising about one-third of Russia's total area. Formall ...
in 2009, but the genus name itself proved to be an illegitimate later
homonym
In linguistics, homonyms are words which are either; '' homographs''—words that mean different things, but have the same spelling (regardless of pronunciation), or '' homophones''—words that mean different things, but have the same pronunciat ...
of plant and
diatom
A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...
genera (1837 and 1925 respectively). Rather than conserve a little-used name, Molinari-Novoa and Sierra introduced the
replacement name
In biological nomenclature, a ''nomen novum'' (Latin for "new name"), replacement name (or new replacement name, new substitute name, substitute name) is a replacement scientific name that is created when technical, nomenclatural reasons have mad ...
''Neoechinodiscus'' in 2020 and made the necessary
new combination
In Taxonomy (biology), biological taxonomy, a combinatio nova (abbreviated comb. nov. or n. comb.) refers to the formal renaming of an organism's scientific name when it is transferred to a different genus, reclassified within a different specie ...
s for both species, leaving the genus ''incertae sedis'' at familial rank within
Helotiales
Helotiales is an order (biology), order of the class Leotiomycetes within the division Ascomycota. The taxonomy within Helotiales has been debated. It has expanded significantly as genomic techniques for taxonomical identification have become mor ...
apothecia
An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. As ...
) that rest on the surface of their lichen hosts rather than sinking into the thallus. Each disc is usually only 0.05–0.15 mm across and looks slightly shaggy because it is clothed in fine, colourless hairs. The narrow rim (a strongly reduced ) contains a distinctive violet pigment that turns blue-grey when a drop of
potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash.
Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which utili ...
solution is applied and reddish-orange in concentrated
nitric acid
Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...
—chemical reactions that make the genus easy to recognise and separate from superficially similar lichen parasites in the
Helotiales
Helotiales is an order (biology), order of the class Leotiomycetes within the division Ascomycota. The taxonomy within Helotiales has been debated. It has expanded significantly as genomic techniques for taxonomical identification have become mor ...
.
Under the microscope, the spore-bearing layer (
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 oth ...
) is suffused with the same violet tint and lacks the iodine-positive layers seen in many other leotiomycete fungi. Sterile filaments (
paraphyses
Paraphyses are erect sterile filament-like support structures occurring among the reproductive apparatuses of fungi, ferns, bryophytes and some thallophytes. The singular form of the word is paraphysis.
In certain fungi, they are part of the f ...
) are simple, septate threads that mingle with the excipular hairs and remain mostly unswollen at their tips. The asci are club-shaped with a long stalk and an evenly thin wall; unlike those of many relatives they show no thickened apex and contain eight
ascospore
In fungi, an ascospore is the sexual spore formed inside an ascus—the sac-like cell that defines the division Ascomycota, the largest and most diverse Division (botany), division of fungi. After two parental cell nucleus, nuclei fuse, the ascu ...
s. These spores are colourless, single-celled and
ellipsoid
An ellipsoid is a surface that can be obtained from a sphere by deforming it by means of directional Scaling (geometry), scalings, or more generally, of an affine transformation.
An ellipsoid is a quadric surface; that is, a Surface (mathemat ...
, typically 5.5–8.5 × 2.5–3 μm, often holding several oil droplets. No asexual
propagule
In biology, a propagule is any material that functions in propagating an organism to the next stage in its life cycle, such as by dispersal. The propagule is usually distinct in form from the parent organism. Propagules are produced by organisms ...
s have been observed. The combination of hairy discs, unusual violet chemistry, thin-walled asci and tiny, aseptate spores distinguishes ''Neoechinodiscus'' from allied genera such as '' Skyttea'' and '' Rhymbocarpus''.