Omphalotus olivascens, commonly known as the western jack-o'-lantern mushroom, is an orange to brown-colored gilled mushroom

Mushroom

A mushroom is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or on its food source. The standard for the name "mushroom" is the cultivated white button mushroom, Agaricus bisporus; hence the word "mushroom" is most often applied to those fungi that...

 native to California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 and Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

. To an untrained eye, O. olivascens appears similar to some chanterelle

Cantharellus

Cantharellus is a genus of popular edible mushrooms, commonly known as chanterelles . They are mycorrhizal fungi, meaning they form symbiotic associations with plants, making them very difficult to cultivate...

s, but unlike the chanterelle, the jack o'lantern mushroom is poison

Poison

In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....

ous. While not lethal, consuming this mushroom leads to very severe cramp

Cramp

Cramps are unpleasant, often painful sensations caused by muscle contraction or over shortening. Common causes of skeletal muscle cramps include muscle fatigue, low sodium, and low potassium...

s, vomiting

Vomiting

Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...

, and diarrhea

Diarrhea

Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...

.

Unlike chanterelles, the jack-o'-lantern mushroom has true gills (rather than ridges) and it can have olive coloration that chanterelles lack; also, Omphalotus species are saprotrophic

Saprotrophic nutrition

Saprotrophic nutrition is a process of chemoheterotrophic extra-cellular digestion involved in the processing of dead or decayed organic matter that occurs in saprotrophs or heterotrophs, and is most often associated with fungi, for example Mucor and Rhizopus...

, grow directly on wood, and are bioluminescent

Bioluminescence

Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...

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A subspecies with blue flesh, O. olivascens var. indigo, was described growing on live oak in Baja California

Baja California

Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...

, Mexico.

A recent molecular study shows the jack-o'-Lantern to be most closely related the Ghost Fungus Omphalotus nidiformis

Omphalotus nidiformis

Omphalotus nidiformis, or ghost fungus, is a gilled basidiomycete mushroom found in southern Australia most notable for its bioluminescent properties. Generally found growing on dead or dying trees, it is saprotroph and parasite....

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