Mycena haematopus, commonly known as the bleeding fairy helmet, the burgundydrop bonnet, or the bleeding Mycena, is a species of fungus in the family Mycenaceae, of the order Agaricales. First described scientifically in 1799, it is classified in the section Lactipedes of the genus Mycena, along with other species that produce a milky or colored latex. The fruit bodies of M. haematopus have caps that are up to 4 cm (1+5⁄8 in) wide, whitish gills, and a thin, fragile reddish-brown stem with thick coarse hairs at the base. They are characterized by their reddish color, the scalloped cap edges, and the dark red latex they "bleed" when cut or broken. Both the fruit bodies and the mycelia are strongly bioluminescent. It is widespread and common in Europe and North America, and has also been collected in old Japan and Venezuela. It is saprotrophic—meaning that it obtains nutrients by consuming decomposing organic matter—and the fruit bodies appear in small groups or clusters on the decaying logs, trunks, and stumps of deciduous trees, particularly beech. The edibility of the species is not known definitively. It produces various unique alkaloid pigments.
Taxonomy The species was initially named Agaricus haematopus by Christian Hendrik Persoon in 1799, and later sanctioned under this name by Elias Magnus Fries in his 1821 Systema Mycologicum. In the classification of Fries, only a few genera were named, and most agaric mushrooms were grouped in Agaricus, which was organized into a large number of tribes. Mycena haematopus gained its current name in 1871 when the German fungal taxonomist Paul Kummer raised many of Fries' Agaricus tribes to the level of genus, including Mycena. In 1909 Franklin Sumner Earle placed the species in Galactopus, a genus that is no longer considered separate from Mycena. Mycena haematopus is placed in the section Lactipedes, a grouping of Mycenas characterized by the presence of a milky or colored latex in the stem and flesh of the cap. The specific epithet is derived from Ancient Greek roots meaning "blood" (αἱματο-, haimato-) and "foot" (πους, pous), owing to the red latex than can easily be produced by breaking the mushroom at the base. It is commonly known as the blood-foot mushroom, the bleeding fairy helmet, the burgundydrop bonnet, or the bleeding Mycena. In 1914, Jakob Emanuel Lange described the variety M. haematopus var. marginata, characterized by the reddish color on the edge of the gills; Mycena specialist Rudolph Arnold Maas Geesteranus considered the coloration of the gill edge too variable to have taxonomical significance. Mycena haematopus var. cuspidata was initially found in Colorado in 1976, and described as a new variety by American mycologists Duane Mitchel and Alexander H. Smith two years later. The fruit bodies are characterized by a "beak" on the cap that often splits or collapses as the cap matures. It was treated as Mycena sanguinolenta var. cuspidata by Maas Geesteranus in 1988.
Description
The fruit bodies of Mycena haematopus are the reproductive structures produced by cellular threads or hyphae which grow in rotting wood. The shape of the cap of the fruit body will vary depending on its maturity. Young caps, or "buttons", are ovoid (egg-shaped) to conical; later they are campanulate (bell-shaped), and as the fruit body matures, the margins (cap edge) lift upward so that the cap becomes somewhat flat with an umbo (a central nipple-shaped bump). The fully grown cap can reach up to 4 cm (1+5⁄8 in) in diameter. The surface of the cap initially appears dry and covered with what appears to be a very fine whitish powder, but it soon becomes polished and moist. Mature caps appear somewhat translucent, and develop radial grooves mirroring the position of the gills underneath. The color of the cap is reddish- or pinkish-brown, often tinged with violet, and paler towards the edge. The margin is wavy like the edge of a scallop and may appear ragged because of lingering remnants of the partial veil. The gills have an adnate attachment to the stem, meaning they are more or less directly attached to it. They are initially whitish or "grayish vinaceous" in color, and can develop reddish-brown stains. Between 20 and 30 gills reach from the cap edge to the stem, resulting in a gill spacing that is described as "close to subdistant"—gaps are visible between adjacent gills. There are additional gills, called lamellulae, that do not extend directly from the margin to the stem; these are arranged in two or three series (tiers) of equal length. The stem is 3–9 cm (1+1⁄8–3+1⁄2 in) tall and 0.1–0.2 cm (1⁄32–3⁄32 in) thick, hollow and brittle, and a dark reddish-brown color. In young fruit bodies, the upper part of the stem is densely covered with a pale cinnamon-colored powder which wears off with age. The stem has a mass of coarse hairs at the base.
The mushroom flesh can range from pale to the color of red wine (vinaceous), and has no distinctive odor. It oozes a red latex when cut or otherwise injured. The flavour is mild to slightly bitter.
Bioluminescence Both the mycelium and the fruit bodies of M. haematopus (both young and mature specimens) are reported to be bioluminescent. However, the luminescence is quite weak, and not visible to the dark-adapted eye; in one study, light emission was detectable only after 20 hours of exposure to X-ray film. Although the biochemical basis of bioluminescence in M. haematopus has not been scientifically investigated, in general, bioluminescence is caused by the action of luciferases, enzymes that produce light by the oxidation of a luciferin (a pigment). The biological purpose of bioluminescence in fungi is not definitively known, although several hypotheses have been suggested: it may help attract insects to help with spore dispersal, it may be a by-product of other biochemical functions, or it may help deter heterotrophs that might consume the fungus.
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