Species Fact Sheet
Common Name:
Scientific Name: Hydnotrya michaelis (E. Fisch.) Trappe
Divivion: Eumycota
Subdivision: Ascomycotina
Class: Discomycetes
Order: Tuberales
Technical Description:
Fruiting Body yellow, yellow-brown to red-brown; subspherical, 10-30(50) mm in
diameter, divided into a couple of cerebriform lobes (reminiscent of Helvella); surface
smooth or finely pubescent; in cross section irregularly labyrinthine, ochre-yellow to
purple-brown, with broad channels, without outside connection, hymenium formed on the
surface of the lobes. Flesh tough, initially with pleasant smell, later with garlic odor.
Spores 8 per ascus, ellipsoid, red-brown and warty at maturity, 20-42 x 15-30 um.
Hydnotrya is one of several genera included among the true truffles (Division
Ascomycota). There are three groups of fleshy fungi with which true truffles may be
confused: 1) puffballs, 2) gastroid agarics, and 3) "false truffles". False truffles,
puffballs and gastroid agarics are included within the Gasteromycetes (Division
Basidiomycota) whose sexually produced spores (usually 4) are born within, rather than
forcibly discharged from meiosporangia called basidia. The spore mass of puffballs
(Lycoperdon and allies) is usually white, firm, and without readily discernable chambers
when young, and becoming powdery and rather quickly dispersed at maturity. The
fruiting bodies of puffballs are usually found aboveground. While the presence of a cap
and stalk is clearly evident in some gastroid agarics, species of Endoptychum,
Brauniellula or Thaxterogaster may bear a stronger resemblance to false truffles.
However, dissection of a gastroid agaric will reveal at least some evidence of a percurrent
stalk (one that extends through the spore mass to the top of the cap). At maturity, the
sporocarps of gastroid agarics are usually found partially or fully aboveground.
Macroscopically, the false truffles most likely to be mistaken for true truffles are those
lacking any evidence of an external or internal stalk. The most common of such false
truffle general is Rhizopogon. However, in contrast to most true truffles, most false
truffle genera, including Rhizopogon, have an interior featuring minute gelatinous or nongelatinous holes or empty chambers. In contrast, most genera of true truffles, including
Hydnotrya, feature 1) an interior that is solid, flakes or chips off like wax and may be
marbled with veins, or 2) an interior composed of one or more large, simple or
convoluted chambers, or 3) a sporocarp wall that is infolded to form numerous empty
canals, veins or cavities that often open to the exterior. Microscopically, true truffles
differ from all Gasteromycete fungi in bearing sexually produced spores (usually 8)
within a meiosporangia called asci. can be distinguished from other genera of true
truffles by the following combination of characters: 1) exterior of sporocarp neither
distinctly hairy or warty, 2) interior of sporocarp hollow or with open (without loosely
stuffed hyphae) veins, canals or chambers formed by complex infolding of the sporocarp
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wall, 3) asci not amyloid (tips staining bluish in iodine solution) and 4) spores
ornamented. Among the several North American species of Hydnotrya, H. cerebriformis,
H. michaelis, H. tulasnei and H. variiformis can be distinguished from H. cubispora by
the presence of a complexly folded or convoluted interior. Hydnotrya cerebriformis and
H. tulasnei can be differentiated from H. variiformis, and H. michaelis by the production
of round (and often knobby), rather than elliptical spores. Mature spores of Hydnotrya
variiformis are described as being yellow-brown and minutely pitted and wrinkled while
those of H. michaelis are said to be red-brown and warty. The rare truffle Hydnotrya
inordinata has a complexly folded and convoluted interior and globose to ellipsoid
yellow-brown spores ornamented with crowded, flexuous, tapered spines.
Life History: Sporocarps maturing in summer, usually gregarious, near tree trunks; may
be slightly emergent from ground surface when fully developed. As with some other
Hydnotrya species occurring in the USA, H. michaelis sporocarps are sometimes found
inside very rotten logs. The frequency of sporocarp occurrence within rotten lots has led
to species of the genus being referred to as "wood truffles".
Range, Distribution and Abundance: British Isles, Europe, Alaska, Colorado,
Montana, Nevada, Idaho, Washington and Oregon. In Oregon, this species is reported
from Anthony Lakes Pass, Wallowa-Whitman National Forest, Baker Co., and Santiam
Sno-Park (west of Santiam summit), Willamette National Forest, Linn Co. In
Washington, the species is reported from Mt. Adams, Skamania Co.
Habitat Associations: Coniferous forests; believed to be ectomycorrhizal with Pinaceae.
At the Santiam Sno-park site in Oregon, this species was reported to be hypogeous under
Tsuga heterophylla. In Colorado and Nevada, Hydnotrya michaelis has been reported in
association with Picea engelmannii, Pinus flexilis, Pinus albicaulis and Abies lasiocarpa.
Collection records in the western USA suggest that this species is found from midmontane to subalpine elevations.
Threats: With the assumption that this species is ectomycorrhizal, it is reasonable to
assume that as with ectomycorrhizal fungi in general, threats to the species particularly
include activities/events that threaten to damage the mycelium. While not entirely
consistent, the literature appears to amply demonstrate that moderate to severe fire,
removal of a large percentage of host plants (with attendant reduction in canopy cover)
and/or of large woody debris, and soil compaction can reduce both the biomass and
species diversity within a community of ectomycorrhizal fungi. Attendant reductions in
production of false truffles may, in turn, potentially reduce dispersal of their spores by
small mammals.
Conservation Considerations: Revisit known localities to confirm persistence and
determine extent of populations. Conduct surveys to locate new populations. Consider
buffering known sites from adjacent vegetation management activities. Consider
vegetation management activities within known site buffer that are likely to maintain or
improve ectomycorrhizal fungal habitat quality (e.g., moderate hand-thinning of an
overstocked stand or augmenting a deficient volume of coarse woody debris). When
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conducting vegetation management activities in areas with good habitat potential,
consider leaving scattered and clumped host trees and ample coarse woody debris while
minimizing soil compaction and burn severity of activity-related fires.
Conservation Rankings and Status:
Global: G3; Oregon: S1
ORNHIC List 3
Prepared by: Rick Dewey, Deschutes National Forest, April 2009
References
Arora, David. 1979. Mushrooms Demystified - A Comprehensive Guide to the Fleshy
Fungi. Ten Speed Press, Berkeley, California. 959 pp.
Castellano, Michael, Jane Smith, Thom O'Dell, Efren Cazares and Susan Nugent. 1999.
Handbook to Strategy 1 Fungal Taxa from the Northwest Forest Plan. U.S. Department
of Agriculture Forest Service, Pacific Northwest Research Station, Portland, OR.
General Technical Report PNW-GTR-476. October 1999.
Cushman, Kathleen and Rob Huff. 2007. Conservation Assessment for Fungi Included
in Forest Service Regions 5 and 6 Sensitive and BLM California, Oregon and
Washington Special Status Species Programs. R6 USFS and OR/WA BLM Interagency
Special Status/Sensitive Species Program (ISSSSP).
http://www.fs.fed.us/r6/sfpnw/issssp/planning-tools/
Evans, Larry. 2009. Montana Truffles. In Winter 2009 edition of Fungal Jungal,
newsletter of the Western Montana Mycological Association.
http://www.fungaljungal.org/truffle.htm
Ferriel, Jenifer and Katie Grenier. 2008. Annotated Bibliography of Information
Potentially Pertaining to Management of Rare Fungi on the Special Status Species List
for California, Oregon and Washington. R6 USFS and OR/WA BLM Interagency
Special Status/Sensitive Species Program (ISSSSP).
http://www.fs.fed.us/r6/sfpnw/issssp/planning-tools/
Fogel, Robert. 1994. Report on Fungi from the Columbia Basin Deposited in the
University of Michigan Herbarium. Interior Columbia Basin Ecosystem Management
Project, Science Integration Team - Terrestrial Staff. December 7, 1994. 21 pp. + 5
appendices.
MICH Fungus & Lichen Database Query for Specimen Data.
http://www.herb.lsa.umich.edu/Bioinformatics.htm
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Oregon Natural Heritage Information Center. 2007. Rare, threatened and endangered
species of Oregon. Oregon Natural Heritage Information Center, Oregon State
University. Portland. 100pp.
http://oregonstate.edu/ornhic/2007_t&e_book.pdf
Snowarski, Marek. 2002. Hydnotrya michaelis. In Atlas grzybow Polski - Mushrooms
and Fungi of Poland.
http://www.grzyby.pl/gatunki/Hydnotrya_michaelis.htm
Trappe, Matt, Frank Evans and James Trappe. 2007. Field Guide to North American
Truffles. Ten Speed Press, Berkeley, California.
Weber, Nancy. 1994. Report on Pezizales (Eumycota, Ascomycotina) of the portion of
the Columbia River Basin in the United States. Interior Columbia Basin Ecosystem
Management Project Science Integration Team - Terrestrial Staff. December 14, 1994.
107 pp.
USDA Forest Service. 1995. Report on Fungi. Prepared by Michael A. Castellano for
Interior Columbia Basin Ecosystem Management Project.
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