Mushroom Monday: Shrimp of the Woods (Entoloma abortivum)

Mushroom Monday: Shrimp of the Woods (Entoloma abortivum)

This week on Mushroom Monday, we dive into one of the most unusual-looking fungi you might encounter: the Shrimp of the Woods (Entoloma abortivum). With its peculiar appearance and fascinating behavior, this mushroom stands apart in the forest floor ecosystem.

Overall Appearance

The overall look of Entoloma abortivum can vary depending on its form. Most often, it is seen as a lumpy, irregular mass known as an “aborted” form. These blobs are dense, firm, and often resemble chunks of seafood, which explains the common nickname “Shrimp of the Woods.” The color typically ranges from off-white to pale gray. Occasionally, the mushroom appears in its “normal” form, which looks more like a traditional mushroom with a cap, gills, and stem.

Cap Appearance

When it forms a traditional mushroom shape, the cap of Entoloma abortivum is pale gray to whitish. It often measures up to 10 cm across and may be broadly convex to nearly flat or slightly depressed in the center. The surface of the cap tends to be smooth, and in some cases, it may appear moist or slightly greasy. As the mushroom matures, the cap may develop faint wrinkles or folds.

Gills or Pores Appearance

The gills of the normal form of Entoloma abortivum are closely spaced and are attached to the stem. They start off pale but transition to a pinkish color as the spores mature. This pink coloration is a notable feature of many Entoloma species. In the aborted form, gills are usually absent or only barely visible, sometimes appearing as small, hidden structures within the lumpy mass.

Stem Appearance

In the normal form, the stem is relatively short and thick compared to the cap, with a whitish to pale gray color that matches the cap. It may measure several centimeters long and often shows a firm, solid texture. In the aborted form, the stem is typically absent or highly reduced, and the structure becomes a single dense mass without clear separation into cap and stem.

Geographic Distribution

Entoloma abortivum is found primarily in eastern North America, including the Midwest and along the Appalachian region. It has been reported from Canada down to parts of the southeastern United States. Although there are no extensive records confirming its presence around Houston, Texas, the hardwood forests of eastern Texas could potentially provide suitable habitat. However, sightings in the Houston area appear to be rare or undocumented.

Relationship to Trees

This mushroom is commonly found in hardwood forests, often near decaying stumps, fallen logs, or buried wood. It tends to fruit in areas rich in organic debris, suggesting a strong association with decomposing tree matter. Rather than forming a symbiotic (mycorrhizal) relationship with living trees, Entoloma abortivum seems to interact more closely with the forest floor itself, particularly where decaying wood is abundant.

Relationship with Other Organisms

Perhaps the most fascinating aspect of Entoloma abortivum is its relationship with other fungi — especially species in the Armillaria genus, often called honey mushrooms. Entoloma abortivum is believed to be mycoparasitic, meaning it parasitizes Armillaria mushrooms. In this interaction, it invades and overtakes the Armillaria tissue, resulting in the creation of the distinctive aborted forms. Studies suggest that this gives Entoloma abortivum a nutritional advantage, although much remains to be learned about the details of this unique fungal battle.

Interesting Facts

One of the most remarkable things about Entoloma abortivum is that the “aborted” form, which looks like a shrimp or a chunk of popcorn, is actually considered the result of a successful parasitic attack. Rather than being a failed fruiting body, the lumpy structure represents a win for Entoloma abortivum over its fungal rival. Moreover, while the normal form of the mushroom is relatively rare to find, the aborted, shrimp-like forms often appear in large clusters when conditions are right and when Armillaria is present.

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