Kalapuya brunnea

Description

Kalapuya brunnea is a species of truffle in the monotypic fungal genus Kalapuya. It was formerly thought to be an undescribed species of Leucangium until molecular analysis demonstrated that it was distinct from that genus.

The truffle is reddish-brown with a rough and warty outer skin, while the interior spore-producing gleba is initially whitish before developing grayish-brown mottling as it matures. Mature truffles have an odor resembling garlicky cheese, similar to mature Camembert. The species has been harvested for culinary purposes in Oregon.

The species is known only from the Pacific Northwest region of the United States, where it grows in Douglas fir forests that are up to about 50 years old. Usually appearing from October through March, fruit bodies grow in the top 2–10 cm (0.8–3.9 in) of soil, beneath soil litter, at elevations ranging from roughly sea level to about 500 m (1,600 ft). It occurs on the west side of Oregon's Cascade Range, as well as in the Coastal Ranges of Oregon and northern California.

Common names: Oregon Brown Truffle.

Mushroom Identification

1. Fruit Bodies

   The truffle-like fruit bodies of Kalapuya are roughly spherical, with lobes and furrows, and dimensions of typically 12–60 mm (0.47–2.36 in) by 10–45 mm (0.39–1.77 in).

2. Peridium

   The peridium (outer "skin") is up to 2 mm thick, and ranges in color from light yellowish-brown to orange-brown to reddish-brown, usually with darker patches in maturity.

3. Surface

   The surface texture is rough, as the truffle is covered with flat to rounded warts that are 0.5–3 mm wide; larger warts often have smaller warts on them. Older specimens develop narrow cracks over the surface such that it becomes areolate or rimose.

4. Undersurface

   The undersurface of the peridium has an branching basal attachment that is roughly similar in texture to cartilage, and which breaks off readily when the truffle is extracted from the soil. The internal spore-bearing tissue, the gleba, is initially whitish and firm but develops grayish-brown mottling as it matures.

5. Edibility

   The truffle is edible and has been harvested for culinary purposes, although with less frequency than other Pacific Northwest truffles. Both the flavor and odor of the edible fruit body resemble mature Camembert cheese. One source described the taste as follows: "Served in melted butter on sliced baguette, they reminded of buttered lobster."

6. Spores

   The spores are ellipsoid in shape, with a smooth surface, and contain a large central oil drop surrounded by smaller droplets. The spore dimensions are 32–43 by 25–38 μm, the walls measuring 1–3 μm thick. Although not reactive with Melzer's reagent, spores stain readily with Methyl blue. The asci contain 6 to 8 spores per ascus. They are variably shaped, with dimensions of 70–110 by 60–100 μm, with a stem 10–40 by 6–10 μm, and a forked base. Initially about 3 μm thick, the ascus walls thin to roughly 1 μm when mature. The gleba comprises loosely interwoven, thin-walled hyaline hyphae measuring 5–13 μm in diameter.

7. Similar Species

   Leucangium carthusianum, the Oregon black truffle, is roughly similar in appearance, habitat, and growing season, but can be distinguished by its darker (charcoal black) peridium. Microscopically, the spores of Leucangium are larger (60–90 μm) and have a single large oil droplet. L. carthusianum is also edible and prized for its taste and aroma.

Photo sources:

Photo 1 - Author: Mary Smiley (ladyflyfsh) (CC BY-SA 3.0)

Photo 2 - Author: Mary Smiley (ladyflyfsh) (CC BY-SA 3.0)