Amanita regalis, commonly known as the royal fly agaric or the king of Sweden Amanita, is a species of fungus in the family Amanitaceae. Common in Scandinavian countries, it is also found in eastern and northern Europe. In North America, its distribution is restricted to Alaska. The fruit bodies of the fungus somewhat resemble the fly agaric (Amanita muscaria), and it was formerly regarded as a variety of this species. A. regalis differs from it in being larger, with a liver-brown cap bearing numerous scabs, and in having a stem which is yellow-ochre at the base, with patches or rings of patches. Chemical analysis has shown that this species contains muscimol, the same psychoactive compound found in A. muscaria.
Taxonomy and naming
Amanita regalis was first described as Agaricus muscarius β regalis by Elias Magnus Fries in his Systema Mycologicum, published in 1821. In 1887, Pier Andrea Saccardo treated it as a variety of Amanita muscaria. Edmund Michael, in 1903, became the first to consider it a distinct species. In 1941, Jean-Edouard Gilbert suggested a complete reorganization of the genus Amanita in his world monograph of the genus, and moved it to Amanitaria as A. muscaria var. regalis. In his original (1949) version of Agaricales in Modern Taxonomy, Rolf Singer considered it a subspecies of A. muscaria, but noted that it may be regarded as a separate species; in the fourth edition (1986), he listed it as a distinct species. A. regalis is classified in a section of Amanita within the genus, a grouping of related Amanitas that have a ring on the stem (or remnants thereof), and a bulb at the base of it. More recently, a Japanese group studied the biogeography of A. muscaria and related species, and, using molecular phylogenetic analysis, concluded that the taxon should be considered a grouping of A. muscaria, rather than a distinct species. However, as of 2012, both Index Fungorum and MycoBank list the taxon as Amanita regalis.
The species has been called by several vernacular names, including the "Brown fly agaric", the "king of Sweden Amanita", or the king fly agaric. In France it is known as Amanite royale, while in Germany it is Königsfliegenpilz. The specific epithet is derived from the Latin word regalis, meaning "royal". In 2000, it was selected by the German Mycological Society as "Mushroom of the Year".
Description
Like all Amanita species, the bulk of the organism lies beneath the ground as a symbiotic partner to certain species of trees. The fruit body of the fungus is a reproductive structure that appears when appropriate environmental conditions of moisture, temperature, and nutrient availability are met. The cap of A. regalis is broad, and, depending on the stage of its development, can range in shape from spherical to convex to somewhat flattened. The color is yellowish brown, and it is densely covered with yellowish to light ochraceous scabby warts, which are arranged in almost regular concentric rings. The rings are a remnant of the volva left behind during expansion of the young fruit body. The cap is fleshy and when mature has grooves on the margin, which can extend . The cap cuticle may be separated from the cap by peeling, to almost the center.
The gills are crowded close together, free from attachment to the stem, and white with a creamy yellow tinge. The edges of the gills are floccose, meaning they have tufts of soft wooly hairs—another volval remnant. The stem of a mature individual is typically between long and wide, and spreads at the base into a bulb ornamented with 2–4 rings of small squamulose, lemon or ochre-yellow warts. The entire stem and ring are not pure white but have a faint yellowish tinge. The flesh is whitish, faintly yellowish in the stem, and golden yellow under the cuticle of the cap. It does not change color in air, and has an insignificant taste and smell.
Microscopic features
The spores are broadly ellipsoid to roughly spherical, hyaline (translucent), smooth, and have dimensions of 9–12 by 7–8 µm. They are non-amyloid, meaning that they do not absorb iodine when stained with Melzer's reagent. The spore-producing cells, the basidia, are club-shaped, measure 38–46 by 3–13 µm, and have clamps at their bases.