''Hydnellum fennicum'' is a species of

tooth fungus The hydnoid fungi are a group of fungi in the Basidiomycota with basidiocarps (fruit bodies) producing spores on pendant, tooth-like or spine-like projections. They are colloquially called tooth fungi. Originally such fungi were referred to the ge ...

in the family

Bankeraceae The ''Bankeraceae'' are a family of fungi in the order Thelephorales. Taxa are terrestrial, and ectomycorrhizal with plant species in families such as Pinaceae or Fagaceae. The family was circumscribed by Marinus Anton Donk in 1961. According t ...

. Native to northern Europe, it forms

mycorrhiza A mycorrhiza (; , mycorrhiza, or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plant's rhizosphere, the plant root system and its surroundings. Mycorrhizae play ...

l associations with

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...

trees. It is recognised by its yellowish‑brown

cap A cap is a flat headgear, usually with a visor. Caps have crowns that fit very close to the head. They made their first appearance as early as 3200 BC. The origin of the word "cap" comes from the Old French word "chapeau" which means "head co ...

covered in fine powdery scales and by downward‑pointing teeth beneath that change from whitish to purplish‑brown. The fungus is considered

critically endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

in Switzerland due to

habitat loss Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...

Taxonomy

It was originally described by the Norwegian mycologist

Petter Karsten Petter Adolf Karsten (16 February 1834 – 22 March 1917) was a Finnish mycologist, the foremost expert on the fungi of Finland in his day, and known in consequence as the "father of Finnish mycology". Karsten was born in Merimasku near Turku ...

in 1882 as a

variety Variety may refer to: Arts and entertainment Entertainment formats * Variety (radio) * Variety show, in theater and television Films * ''Variety'' (1925 film), a German silent film directed by Ewald Andre Dupont * ''Variety'' (1935 film), ...

of '' Sarcodon scabrosus''. Karsten promoted it to a distinct species in 1887.

Description

''Hydnellum fennicum'' produces fruit bodies (

basidiocarp 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 no ...

s) that occur singly or in small clusters. The cap ( pileus) grows up to 10 cm in diameter and often develops a shallow central depression. Its surface is densely covered in fine, powdery scales—those in the centre tending to stand upright, while those towards the margin lie flat. Young caps are

ochre Ochre ( ; , ), iron ochre, or ocher in American English, is a natural clay earth pigment, a mixture of ferric oxide and varying amounts of clay and sand. It ranges in colour from yellow to deep orange or brown. It is also the name of the colou ...

‑yellow, but they darken to yellow‑brown over time and may show patches of reddish‑brown. Beneath the cap, 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 (; 18 July 16353 March 1703) was an ...

is composed of slender, downward‑pointing spines (or "teeth") up to 5 mm long; these start off whitish and gradually deepen to purplish‑brown. The

flesh Flesh is any aggregation of soft tissues of an organism. Various multicellular organisms have soft tissues that may be called "flesh". In mammals, including humans, ''flesh'' encompasses muscles, fats and other loose connective tissues, ...

(context) is white throughout but shows greenish to greyish tones at the base of the stem ( stipe), and emits a faint bitter‑almond smell when fresh. The stipe is cylindrical, measuring 3–7 cm tall by 1–3 cm thick. It is initially tomentose—that is, clothed in a soft, woolly mat of hairs—but becomes smooth (glabrous) with age. Its colour matches the cap except at the very base, which often turns bluish‑green to greyish‑green and may be overlaid by pale mycelium (the fungal network). Under the microscope, the cap tissue comprises simple

septate In biology, a septum (Latin for ''something that encloses''; septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interatrial se ...

hyphae—thread‑like cells divided by cross‑walls—up to 20

μm The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...

wide. The spores formed on the spines (basidiospores) are pale brown, sharply angular in outline, and measure roughly 6.3–7.6 by 4.5–5.2 μm.

Habitat and distribution

''Hydnellum fennicum'' is distributed primarily in continental Norway and eastwards. It forms

ectomycorrhiza An ectomycorrhiza (from Greek ἐκτός ', "outside", μύκης ', "fungus", and ῥίζα ', "root"; ectomycorrhizas or ectomycorrhizae, abbreviated EcM) is a form of symbiotic relationship that occurs between a fungal symbiont, or mycobio ...

e with

. It is considered

in Switzerland.

References

{{Taxonbar, from=Q10430338 fennicum Fungi described in 1882 Fungi of Europe Inedible fungi Taxa named by Petter Adolf Karsten Fungus species