Chicken fat mushroom

Appearance

The mushroom can be recognized by the bright yellow cap with red to reddish-brown scales embedded in slime, the large yellow angular pores on the underside of the cap, and the narrow yellow stem marked with dark reddish dots. Molecular phylogenetics analysis suggests that ''S. americanus'' may be the same species as ''S. sibiricus'', found in western North America and western and central Asia. ''Suillus americanus'' is edible, although opinions vary as to its palatability; some susceptible individuals may suffer a contact dermatitis after touching the fruit bodies. The fruit bodies contain a beta glucan carbohydrate shown in laboratory tests to have anti-inflammatory properties.

The cap is typically between 3–10 cm in diameter, broadly convex with a small umbo to flat with age. The cap margin is curved inwards in young specimens, and may have remnants of a yellowish, cottony veil hanging from it. The cap surface is colored bright yellow with red or brownish streaks and hairy patches. When the fruit body is young and moist, the surface is slimy; as the cap matures and dries out, it becomes sticky or tacky.

The tubes which comprise the pore layer on the underside of the cap are 0.4 to 0.6 cm deep, and have an adnate to decurrent attachment to the stem. They are yellow, and stain reddish-brown when bruised. The yellow pores are large and angular, and tend to become darker as they age. The pores are slightly wider than long, so that there are about 9–10 pores per centimeter measured radially, but 12 to 13 per centimeter when measured tangentially, about halfway to the edge. As is the case with all boletes, spores form on the inner surfaces of the tubes and sift through their openings to be borne away on the air currents outside.

The stem is 3–9 cm by 0.4–1 cm , roughly equal in width throughout, often crooked, and becomes hollow with age. The color of the stem surface is lemon yellow, and it is covered with glandular dots that bruise if handled. The partial veil is not attached to the stem, and usually does not leave an ring on the stem. A whitish mycelium present at the base of the stem helps anchor the fruit body in the substrate. The flesh is mustard yellow, and stains pinkish-brown when cut or bruised.In deposit, the spores are cinnamon-colored. Viewed with a microscope, they are pale yellow, smooth, and roughly elliptical in shape, and measure 8–9.5 by 3.5–5 µm. The basidia, the spore-bearing cells, are club-shaped and 4-spored, with dimensions of 21–25 by 5.5 to 6 µm. The pleurocystidia range in shape from cylindrical to club-shaped and are arranged in bundles. Both the bases of the bundles and the surface of the cystidia may be covered with brown pigment particles. Cheilocystidia are cystidia located in the gill faces. In ''S. americanus'', they are mostly club-shaped, often with an expanded apex, and like the pleurocystidia, are arranged in bundles, with brown pigment particles at the base of the bundles. Bundles of cystidia near the tube openings may sometimes be visible with a hand lens. Like all ''Suillus'' species, the cystidia of ''S. americanus'' will turn orange-brown in the presence of a solution of 3% potassium hydroxide. The slimy layer on the cap surface results from an interwoven layer of gelatinous hyphae that are typically 3–5 µm thick.

Naming

''Suillus americanus'' is very similar in appearance to ''Suillus sibiricus'' but the latter species associates with ''Pinus monticola'' and ''Pinus flexilis'' rather than ''Pinus strobus''. One field guide suggests that ''Suillus sibiricus'' has a thicker stem than ''S. americanus'', brown spots on the cap, and is a darker, more dingy yellow. Molecular phylogenetics analysis has shown, however, that specimens of ''S. sibricus'' collected from China and western North America, as well as ''S. americanus'' from eastern North America, are most likely "a single circumboreal taxon".

Another lookalike species is ''Suillus subaureus'', which can be distinguished microscopically by slightly smaller, hyaline spores , and an association with Quaking Aspen .

Distribution

''Suillus americanus'' is a common species, and is found growing solitarily or in clusters on the ground throughout northeastern North America, north to Canada, where it typically fruits in the late summer and autumn. It is also found in Guangdong, China, an example of a disjunct distribution. Fruit bodies can often be found in drier weather when other species are not abundant.

''Suillus americanus'' is a mycorrhizal species, a mutualistic relationship where the fungus forms a sheath on the surface of the root from which hyphae extend outward into the soil, and inwards between the cortical cells with which they interface to form a Hartig net. The main benefit for the fungus is constant access to a supply of carbohydrates produced by the plant's photosynthesis, while the plant benefits from an enhanced supply of mineral nutrients from the soil, taken up by the hyphae of the fungus. It grows in association with pines, particularly eastern white pine .

Habitat

''Suillus americanus'' is a common species, and is found growing solitarily or in clusters on the ground throughout northeastern North America, north to Canada, where it typically fruits in the late summer and autumn. It is also found in Guangdong, China, an example of a disjunct distribution. Fruit bodies can often be found in drier weather when other species are not abundant.

''Suillus americanus'' is a mycorrhizal species, a mutualistic relationship where the fungus forms a sheath on the surface of the root from which hyphae extend outward into the soil, and inwards between the cortical cells with which they interface to form a Hartig net. The main benefit for the fungus is constant access to a supply of carbohydrates produced by the plant's photosynthesis, while the plant benefits from an enhanced supply of mineral nutrients from the soil, taken up by the hyphae of the fungus. It grows in association with pines, particularly eastern white pine .