Amanita dunensis - Amanitaceae.org - Taxonomy and Morphology of Amanita and Limacella
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name Amanita dunensis
name status nomen acceptum
author R. Heim ex Bon & Andary
english name "Dune Death Cap"
intro The following is based on the original description by Bon & Andary (1983).
cap The cap of Amanita dunensis is (20-) 30 - 50 (-70) mm wide, not very fleshy, quickly becomes planar or depressed in the center, pale green which ranges from a whitish-green to a ochre-olivaceous, with the presence of imbedded radial fibers, with a thin and distinctly striate margin.  Volval remnants are absent; microscopically, the cap may retain some hyphae of the volva.  The flesh is white.
gills The gills are broad in the middle, narrow at the ends, just attached to the stem, white, with an irregular edge.  The short gills are numerous and not truncate.
stem The stem is (40-) 50 - 70 (-80) × (3-) 5 - 8 (-10) mm, cylindric or very slightly narrowing upward, whitish or silvery, undecorated or with pale ochraceous fibers on the stem in a snake skin-like or flame-like pattern.  The bulb is minimal.  The ring is skirt-like, whitish, fragile, slightly striate on the upper surface.  The volva is limbate, rather fragile, and white.  The flesh is white.
odor/taste No noticeable odor even in age or while drying.  This species is probably deadly POISONOUS and should be assumed so.
spores The authors provide the following spore measurements: (7-) 8 - 10 (-11.5) × (5.5-) 6 - 7.5 (-8) µm and are broadly ellipsoid to ellipsoid and amyloid.  Clamps are absent at bases of basidia.
discussion This species was originally collected in the departement Vendée, France where it was associated with pine (Pinus pinaster) or oak (Quercus ilex) in dunes along the Atlantic coast.  According to Neville and Poumarat (2004), this species is known only from France and Portugal on the Atlantic and Mediterranean coasts in sandy soil, 10 - 100 meters from the ocean where it occurs with pine, oak and Cistus.

Bon and Andary considered the present species distinct from Amanita phalloides (Fr. : Fr.) Link because of the marginal striations of the cap and the fact that they found no amatoxins in a dried specimen and more phalloidin than they considered usual for A. phalloides.  The remainder of their argument that A. dunensis is a distinct species is based upon the striate margin, the thin stature, and the pale coloration of the cap.  Considering that the mushroom was found growing in the dunes, the supposed macroscopic difference with A. phalloides might be used instead to argue that the specimens were simply depauperate examples of the latter species.

Neville and Poumarat (2004) describe a greater range of size of the fruiting bodies than in the original description and say that the caps are not always striate at first and may only be striate here and there on the margin at maturity.  In addition, they say nonstriate and striate caps can be found in a single collection. Moreover within a single cap, the striations can be of extremely uneven length.  This suggests that striations are related to the drying of the cap in an area exposed to direct sunlight.  This environmental consideration can also contribute to the pale colors in the cap.

The stem length may not be genetically determined.  One occasionally sees specimens of very different species of Amanita with stems abnormally elongated in order to pass around an obstacle such as a rock or a root and get the mushroom's cap out of the substrate.  RET has never examined a specimen of A. dunensis.

We agree with Neville and Poumarat that molecular comparison to A. phalloides would be valuable.  We are not aware of anyone repeating Andary's assay of toxins in the present species.  It would be worth while to perform such an assay on recently collected material.—R. E. Tulloss and L. Possiel
brief editors RET

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