What Is Hypomyces? The Parasitic Fungi That Specialize In Transformation

There’s a lot of weird in the fungi world, and Hypomyces fungi are the source of a lot of funky happenings. Hypomyces species essentially hijack their fungal hosts, altering their appearance so dramatically that identifying the original mushroom becomes nearly impossible.

They are parasites that attack and transform other mushrooms into something totally different from the original. You might have encountered some of the better-known Hypomyces species without even realizing it. The lobster mushroom (Hypomyces lactifluorum) and the bolete eater (Hypomyces chrysospermus) are two prime examples of these parasitic species that dramatically alter their host fungi.

The Hypomyces fungi are known as mycoparasites, fungi that attack other fungi. They are found across Europe, North America, Australia, and parts of China. There are currently 53 species identified across the world. Of the 53, the 23 species that parasitize bracket and crust fungi aren’t usually host-specific. They’ll be more opportunistic and less choosy about their host. However, the ones that target boletes and gilled mushrooms tend to be quite selective, often limiting themselves to a specific host family or genus.

What Is Hypomyces?

The genus Hypomyces belongs to the family Hypocreaceae. These specialized fungi are one of the most distinctive groups of mycoparasites in the fungal kingdom. Hypomyces species are commonly found in both temperate and tropical regions, but the genus has higher species diversity in temperate areas.

Hypomyces are exclusively parasitic fungi that live on other mushrooms. They do not parasitize other plants, trees, or organisms; only other fungi. The parasitic Hypomyces grows over the surfaces of other mushrooms as powdery tissues and pimply crusts. They are obligate parasites, meaning they can only grow on specific fungal hosts. When a Hypomyces species infects a host mushroom, it often causes a systemic infection and the host’s fruiting body is essentially mummified.

The fruiting bodies of these parasitic mushrooms are very small and hard to notice. Each little mushroom sac is around 0.04 inches (1 mm) wide and tall. However, the little fruiting bodies work together in large groups. They form large clusters on the fruiting bodies of their host fungi. And, in doing so, they change both the shape and color of the host into something completely different from its original appearance.

From a scientific point of view, Hypomyces are a key model for learning about how fungi act as parasites and how they interact with their hosts. They are also being researched for possible medical uses. The active compounds from Hypomyces chrysospermus may have cancer-fighting, germ-fighting, and antioxidant effects, including preventing the spread of cancer and stopping cell growth.

Some species, such as H. mycophilus and H. perniciosus, are problematic for mushroom farmers. These are pathogens that affect commercially grown mushrooms.

What Makes Hypomyces Unique?

What sets Hypomyces apart from other parasitic fungi is its incredible ability to completely transform its hosts. Each species typically has a preference for a specific host type. The species that parasitize boletes or agarics tend to be quite selective in their choice of host.

Hypomyces also has a very interesting dimorphic lifecycle. It has both sexual and asexual stages (also called teleomorphic and anamorphic stages). In the asexual stage, the fungus reproduces by cloning, while in the sexual stage, it reproduces through spores.

The transformation effect on hosts is dramatic and distinctive. For example, when Hypomyces infects Amanita mushrooms, the Amanita caps become deformed and stunted. In Russula hosts, Hypomyces growth fills the gaps between the gills, often until you can’t even tell there were gills to begin with. When Hypomyces attack boletes, the cap development of the bolete is often entirely stunted. In all cases, the host mushroom’s spore formation (reproduction) and dispersal are hindered or completely prevented.

How Hypomyces Parasitizes Other Fungi

Parasitic fungi, such as Hypomyces, attack living organisms, penetrate their defenses, and obtain nourishment from living cells. This process can cause disease and sometimes lead to the death of the host.

The parasitic fungi form symbiotic relationships with other living organisms. However, they benefit at the detriment of their host. In the fungal world, fungi that feed on other fungi exhibit a behavior known as mycoparasitism. Hypomyces is a prime example of this phenomenon. They are mycoparasites that target a diverse range of fungal hosts, including Boletes, Russulas, and Polypores.

Most species of Hypomyces are obligatory parasites, meaning they can grow only on specific fungal hosts. Host specificity varies across the genus—some species, like H. microspermus, are highly selective, infecting only specific mushroom groups, such as the Xerocomus chrysenteron group. On the other hand, those like H. chrysospermus act more as generalist pathogens.

The infection process starts when Hypomyces spores land on a suitable host mushroom. When encountering a potential host, they use a set of special enzymes and structures to invade their targets. When they break through the host mushroom’s defenses, they create a mycelial network inside the affected tissue.

After that, the parasitic fungus grows rapidly, typically starting at the base of the stem and progressing upward to take over the gills (or pores) and cap. The parasites often cause a widespread infection that eventually leads to the complete mummification of the host’s fruiting body. The mycoparasite then spreads its infection to healthy mushrooms through the underground mycelium (the mushroom’s “roots”).

Many species go through a guttation phase. Guttation is small drops of moisture on the mushroom, especially when it is just starting out and growing quickly. The drops are usually small and a reddish-amber color.

This guttation is easiest to see when the Hypomyces colony is spreading on its host, mainly along the stem and gills. The guttation process has several ecological roles, such as keeping moisture levels, controlling internal functions, and possibly releasing helpful compounds that assist in taking over the host mushroom.

Once established, the parasitic fungus dramatically transforms its victims. The parasite often so transforms its mushroom host that it becomes difficult to tell what the original mushroom was. The transformation varies depending on the host type:

• In Amanita mushrooms, Hypomyces infection causes the cap to become deformed and stunted. The end result is often shapes resembling human male genitalia.
• When the parasite attacks Russula hosts, the gaps between the folds of the host’s gills become filled with the mycelium of Hypomyces. This creates the characteristic ridged marks of the parasitized mushroom.
• For the boletes Xerocomus and Boletus, the development of the mushroom cap is frequently suppressed. Then, the pores on the underside of the host’s cap are filled with Hypomyces mycelium. The H. chrysospermus-infected mushrooms sometimes develop into spherical forms. They are gray-white and significantly larger in size and weight than normal fruiting bodies.

In all cases, the host mushroom’s ability to make and spread spores is blocked or completely stopped. This disruption of the host’s reproductive process is the final win for the parasite. It essentially hijacks the host’s resources to help itself grow and reproduce, rather than allowing the host to complete its lifecycle.

Visual Characteristics of Hypomyces

Hypomyces species produce a wide and rather remarkable spectrum of colors when infecting their hosts. But there is so much more than just color changes. These parasitic infections radically alter the texture and surface features of host fungi.

The most distinctive textural change is the development of small, flask-shaped fruiting bodies called perithecia. These structures appear as tiny pustules on the surface of the infected host, giving it a fine, sandpaper-like feeling to the touch. The surface of infected mushrooms often develops cracks and folds that aren’t present in the uninfected host.

1. Hypomyces lactifluorum, commonly known as the lobster mushroom, transforms its white mushroom host to a vivid reddish-orange hue. This drastic color change makes the mushroom resemble a cooked lobster shell. As these infected mushrooms age, their color changes from bright orange to purple-red or even wine-purple in extremely old specimens.
   
   The parasite creates a hard, shell-like exterior that completely transforms the host’s consistency. The gills of the host disappear entirely and are replaced by a smooth or slightly bumpy surface covered with tiny pimples. This crusty exterior is remarkably firm, similar to the texture of a young, fresh potato.
   
2. Hypomyces chrysospermus, which primarily targets boletes, initially appears as a white, powdery, mold-like covering. It gradually turns golden yellow and finally matures to a reddish-brown color. This transformation completely engulfs the host bolete, making it virtually impossible to identify the original mushroom.
   
   As the infection progresses, mature specimens often develop a ring of fine white powder around them or have this powder encrusted on the lower portion of the mushroom. Despite appearing like mold, this powder actually consists of the parasite’s spores.
   
3. Hypomyces luteovirens creates a distinctive yellowish to greenish-yellow powdery coating on Russula species. The coating is primarily on the gills and stem. The cap is usually relatively unchanged. This selective colonization creates a striking contrast between the natural cap color and the parasite’s yellow-green infection.
   
4. Hypomyces cervinigenus, which prefers members of the Helvella genus (false morels and allies), initially shows up whitish or pinkish. As it matures, it turns a pale brown color.
   
5. Hypomyces hyalinus transforms its host into a white to pink-tinged mold that completely covers the mushroom. This species creates an especially dense covering that distorts its host into thick, club-like formations. The structural modification completely alters the typical mushroom shape into something barely recognizable as a fungal fruiting body.

Where To Find Hypomyces

The specific habitats are very different for each Hypomyces species because of which host species they prefer to host. Hypomyces lactifluorum (lobster mushroom) grows in wooded areas where its host mushrooms, Russula brevipes or Lactarius species, are found. In the Southwest and Pacific Northwest, though, you often find the lobster mushroom parasite in conifer forests, mainly under ponderosa pine trees.

Hypomyces chrysospermus, which targets bolete mushrooms, is most commonly encountered alongside its favored hosts Xerocomellus zelleri, Xerocomellus chrysenteron, and Xerocomus subtomentosus. Hypomyces cervinigenus, on the other hand, typically attacks Helvella species.

Most of these species have distinct seasonal patterns, with peak fruiting periods during summer and fall months. For instance, lobster mushrooms typically appear from July through October.

The amount of rainfall in a year plays a crucial role in triggering the appearance of Hypomyces. Hypomyces chrysospermus, that one that mummifies bolete mushrooms, is most prevalent during wet years. Moisture stimulates both the host mushroom development and the subsequent parasitic infection.

Ecological Role Of Hypomyces Fungi

These parasitic fungi play important roles in forest ecosystems. Hypomyces species help recycle nutrients by breaking down other fungi. They are decomposers of decomposers. This process returns more nutrients to the soil. By feeding on and altering host fungi, these parasitic mushrooms influence the diversity and abundance of fungi. Their actions help control how many of certain mushroom species there are, which can stop one type of fungus from taking over local ecosystems.

Though Hypomyces fungi do not directly attack wood, many types have indirect connections with woody materials through their host fungi. You can find them in both hardwood and conifer forests. They are often close to decaying logs or stumps that support their host mushrooms. The parasitic fungi grow only on the forest floor, not directly on trees or logs. Their presence indicates that the conditions are suitable for mycoparasitism. This includes the right moisture levels, temperature ranges, and the availability of host fungi.

Life Cycle and Reproduction of Hypomyces

These parasitic fungi use both sexual and asexual reproduction methods, which allows them to efficiently spread and colonize host mushrooms.

The lifecycle of Hypomyces includes three types of spores—two asexual and one sexual—each with different roles in the fungus’s reproduction and survival. These different spore types help the parasite live in various environmental conditions and take advantage of different colonization chances.

In the sexual phase, Hypomyces makes perithecia, which are small flask-shaped structures that look like tiny dark bumps on the mushroom’s body. Inside these perithecia are long, tube-like structures called asci. Each asci holds eight spores. As the mushroom matures, many asci form inside each mushroom body. They then push the spores out through a small hole at the top of the body.

For most species, asexual reproduction is the main method of reproduction. These asexual spores are called “thick-wall spores” because they have a strong cell structure. The thick-walled cells help them stay inactive (hibernate) and survive in tough conditions. This ability allows the fungus to survive until it can find the right host mushrooms to infect.

Throughout their complex lifecycle, Hypomyces species alternate between two distinct stages: asexual (anamorph) and sexual (teleomorph). Initially, the fungus exists in its asexual form and reproduces through cloning. As it matures, it transitions to sexual reproduction.

Example: Hypomyces chrysospermus has three clear lifecycle stages. First, a white fluffy mold covers the host bolete mushroom. Next, a bright yellow powdery layer appears on the surface. Both the white and yellow stages are the asexual forms of the parasite. In the final stage, the mushroom forms a soft, creamy, gray to light khaki skin-like layer with small, dark bumps—these are the fruit bodies where sexual spores are produced.

This final teleomorphic stage often goes unnoticed or is ignored because it typically develops after the host has decayed beyond recognition. Boletes are usually gross, slimy, and smelly at this point. Many Hypomyces species (particularly those attacking boletes) are rarely encountered in their sexual stage. Others are seldom found in their asexual form.

Because the lifecycle stages of Hypomyces species can look so different physically, it can be hard to accurately identify them. Since scientists started putting names to fungi, Hypomyces has always caused problems. If you see a lobster mushroom, it is almost impossible to believe it was once a Russula or Lactarius.

Notable Species of Hypomyces

Hypomyces lactifluorum (lobster mushroom)

The most famous member of the genus, Hypomyces lactifluorum, transforms its host into a bright reddish-orange color resembling a cooked lobster shell. This parasite primarily infects Russula brevipes and Lactarius piperatus species. Unlike its appearance might suggest, it’s neither a lobster nor technically a mushroom but a parasitic fungus that completely alters its host’s appearance. The lobster mushroom is a choice edible and is commercially marketed.

Hypomyces chrysospermus

Commonly called the “bolete eater,” H. chrysospermus parasitizes bolete mushrooms throughout Eurasia, North America, and Australia. It forms a thin white crust layer first. Then, it progresses to golden yellow and finally a reddish-brown pimpled appearance. This species isn’t edible and may be poisonous. Interestingly, it’s used in traditional Chinese medicine to stop bleeding when applied topically to wounds.

Hypomyces cervinigenus

H. cervinigenus exclusively targets elfin saddle (Helvella) mushrooms. It starts out as a white, loose, cottony crust. Later, it becomes more compact as its reproductive structures develop.

Hypomyces polyporinus

This species specifically targets bracket fungi in the genus Trametes. It forms a distinctive white, web-like structure on the surface of the host polypore. Unlike other Hypomyces, this species doesn’t always significantly change the appearance of the host mushroom. This white to buff or tan colored thin crust-like formation may extend across multiple adjacent fruiting bodies without causing obvious changes to the host’s appearance.

Hypomyces camphorati

This species parasitizes Lactarius camphoratus. It forms a white crust on the host mushroom. Then, the crust turns yellow and completely covers the host’s gills. It causes significant deformation. The end result is an irregular shape with a pinkish-brown cap. The stem also gets lighter than the cap and has an irregular, darker zone where the parasite and gills meet.

Hypomyces completus

Hypomyces completus grows on boletes, typically Suillus spraguei in North America. Its crust formation ranges from white to yellow-brown, greenish-brown, brown, to black.

Hypomyces hyalinus

This host-specific pathogen exclusively attacks Amanita species. The infection thoroughly disfigures its host. It causes the Amanita’s cap to grow wider and fuse to the stem. The Hypomyces then covers the entire fruiting body of the Amanita with a crust-like growth that destroys the host’s gills and prevents spore dispersal. This species is found across eastern Canada, the northern United States, and eastern Asia.

Hypomyces transformans

H. transformans only attacks boletes. It is similar to H. chrysospermus but has some differences. This parasite is white to pinkish, dull yellowish, or brownish to brown when fresh.

Hypomyces lateritius

Known as the “ochre gillgobbler,” this species parasitizes specific Lactarius mushrooms. It forms a whitish crust over the gills of its host, which prevents gill formation. The crust also usually deforms the cap and stem. The crust starts out white to beige in color and then darkens to brick red or reddish-brown with age. It is widespread across North America.

Hypomyces luteovirens

This species only infects Russula mushrooms, especially the purple and red types. It looks like a bright yellow-green, powdery mold that slowly covers the stem and gills of the host mushroom. However, the cap surface usually stays the same and is not affected. The inside of the mushroom becomes very firm and shows unique yellow pits that are not usually found in Russula mushrooms. As it gets older, the bright yellow-green color changes to olive green or greenish brown.

Can Hypomyces Be Useful to Humans?

Several Hypomyces species offer practical benefits beyond their role in forest ecosystems. These unique parasitic fungi present surprising utilities in both culinary applications and agricultural management.

Edibility and culinary value

The majority of Hypomyces-infected mushrooms are not edible (and may be toxic), but there are several that are edible and very good.

Hypomyces lactifluorum, commonly known as the lobster mushroom, is a prized edible species with its light seafood-like flavor and dense, firm texture. This parasitic fungus transforms unpalatable mushrooms into culinary delights. The host mushroom, Lactarius piperatus, is very spicy and hot to the taste. But the heat goes away completely with the parasitic takeover.

Fresh lobster mushrooms are absolutely delicious and can be sautéed, grilled, or added to soups and stews. They have a substantial, dense texture that makes them ideal for grating like potatoes to make mushroom patties or latkes. The bright orange coating is also fun because it turns butter or cream a brilliant shade of orange when cooked.

Biocontrol potential in agriculture

Agricultural researchers have found Hypomyces species to be good biological control agents. These fungi are related to the Trichoderma genus, which naturally kills harmful fungi such as Verticillium and Pythium. They could help improve pest management.

Scientists from the Agricultural Research Service also are researching three new Hypomyces species that could be useful. These species may serve as an alternative to methyl bromide. This commonly used pesticide is no longer employed due to environmental concerns. There is also ongoing research examining the potential use of Hypomyces biology for agricultural purposes.

Common Questions About Hypomyces Fungi