#197: Tolypocladium ophioglossoides, The Golden Thread Cordyceps

Tolypocladium ophioglossoides can be distinguished from similar mushrooms by its black/brown colors, pimply head, and golden rhizomorphs that connect to Elaphomyces truffles.

Tolypocladium ophioglossoides (also called Cordyceps ophioglossoides and Elaphocordyceps ophioglossoides) is a fun little mushroom to find, but you have to be paying attention to enjoy it. Unlike most fungi that were placed in Cordyceps, which were insect parasites, T. ophioglossoides – commonly known as the “Golden Thread Cordyceps” (even though it is no longer in that genus) – attacks other fungi. Specifically, it parasitizes truffles in the genus Elaphomyces. If you can spot this tiny brown/black mushroom, make sure to dig it up carefully and follow the golden thread that attaches the mushroom to its truffle host.^1,2

Collecting Tolypocladium

The first thing you do when you find a mushroom is assess its surroundings and substrate (i.e. is it terrestrial or growing on wood, what trees are nearby, etc.). But what is the second thing you do? My next instinct is to pick up the mushroom – being careful to dig up the whole base – to examine it more closely. But this is wrong! The second thing you should do is decide whether or not it is a Cordyceps or Ophiocordyceps relative.

Mushrooms related to Cordyceps and Ophiocordyceps are always attached to an insect or fungal host underground. You should make sure to dig out the subterranean attachment whenever you find one of these mushrooms because it is fun and it can help you identify your otherwise not very descriptive mushroom. Unfortunately, most mushroom hunters – myself included – have the unfortunate habit of unceremoniously plucking these mushrooms from the ground, expecting them to be a coral or earth tongue (which do not require careful excavation). By the time we inspect the mushroom more closely, there is usually no way to go back and find the buried remains.

The Golden Thread Cordyceps has a pimply head with brown and black colors, a smooth stipe, and yellow threads extending out from the base.

So, how do you tell if something is a (Ophio)Cordyceps relative? These mushrooms are usually small and thin and have a pimply head. The pimples are actually tips of flask-shaped spore producing cavities called perithecia. No basidiomycete mushrooms have perithecia and only certain ascomycetes do, so identifying these structures helps narrow down the possibilities. Additionally, most (Ophio)Cordyceps relatives are vaguely shaped like clubs, but many have unusual branching patterns that make them look alien.

Of course, there are many other little ascomycetes that could fit this description; even (Ophio)Cordyceps experts can’t tell for sure without finding the insect or truffle to which the mushroom is attached. Since finding the parasitized organism is the only way you can be sure you’ve found a (Ophio)Cordyceps, you should carefully dig up every specimen that has a distinctly pimply head – a few of them might actually be in the Cordyceps or Ophiocordyceps families!

Description

T. ophioglossoides is a small mushroom that belongs to the earth tongue look-alikes (ETLAs, FFF#037) morphological group. Like other ETLAs, the Golden Thread Cordyceps has two regions on its fruiting body: a sterile stipe and a spore-producing head. In T. ophioglossoides, the stipe and head are not very well defined and the two regions blend into one another. However, the head is somewhat swollen, which makes the mushroom look like a club or a misshapen tongue. Although the Golden Tread Cordyceps can grow up to 8cm long and 1cm wide, it is usually much smaller and thinner than that.^1,2

When young, T. ophioglossoides mushrooms are smooth and reddish brown with only a slight swelling to differentiate the head from the stipe. As the mushroom grows, it gets darker and becomes black with a swollen and pimply head. The stipe remains smooth and often has shades of red-brown and/or yellow, especially near the base. The most distinctive feature of this mushroom is the bright yellow rhizomorphs that connect to the base of the stipe. This feature earned the Golden Thread Cordyceps its common name.^1,2

Ecology

If you carefully dig out the yellow rhizomorphs, you will find that they lead from the base of the mushroom to what looks vaguely like a tiny (and maybe hairy) potato. This structure is actually a truffle from the genus Elaphomyces that is being parasitized by the Golden Thread Cordyceps.^1–3 Cut open this truffle and you will find that the center is filled with loose white mold instead of the dense marbled tissue you expect from truffles. The mold is the part of T. ophioglossoides actually attacking and decomposing the truffle.

T. ophioglossoides feeds off of Elaphomyces truffles. The white mold inside the sectioned truffle is the Golden Thread Cordyceps decomposing the truffle.

T. ophioglossoides fruits in late summer and fall under various trees (mostly oaks and pines) in Eastern North America. Elaphomyces truffles are mycorrhizal fungi that are common symbionts with pines and oaks and less frequently with other trees. Because the Golden Thread Cordyceps gets all its nutrients from attacking the truffles, it grows only under trees that support its hosts.^1,3

Similar Species

There are a whole host of species that are similar to T. ophioglossoides. Black earth tongues, Dead Man’s Fingers (FFF#005), and species from Cordyceps and Ophiocordyceps can all easily pass for T. ophioglossoides, especially when old. The golden threads attached to the base of T. ophioglossoides mushrooms, however, easily distinguish it from those mushrooms. Of course, the trick with the Golden Thread Cordyceps is to excavate it carefully enough to actually see the threads…

Edibility

As far as I know, this mushroom is not edible or used for anything. There are numerous studies examining extracts from T. ophioglossoides for potential medicinal benefits, but I haven’t heard of anyone actually using it medicinally.

Evolution

Based on its genetic relationships to other mushrooms, mycologists believe T. ophioglossoides evolved to parasitize truffles from an ancestor that parasitized insects. The genera most closely related to Typocladium contain mostly entomopathogenic insects, so insect parasitism appears to have evolved first in this lineage. Then, about 50-70 million years ago (which is fairly recent, evolutionarily speaking), the first Typocladium switched from an animal host to a fungal host.⁴ Mycologists are still not sure how the Typocladium lineage was able to accomplish this “host switching” event. The theory is that the insect hosts and the truffles live in the same habitat (namely, on tree roots), so the Typocladium didn’t have to go very far to find a new type of host.⁵

Left: Young T. ophioglossoides showing its smooth texture and light colors.
Right: An old specimen with a distinctly pimply head.

Taxonomy

In recent years, DNA evidence has dramatically altered how Cordyceps is classified. In 2014, the Golden Thread Cordyceps was moved to its current genus, Typocladium. Before that, belonged to Cordyceps or Elaphocordyceps and many sources still use one of those two names for this fungus.² Cordyceps has now been broken up into two distinct lineages that are closely related but different enough to be placed in two separate families. Typocladium was assigned to the family Ophiocordycipitaceae, which mostly includes insect pathogenic fungi like the “Zombie Ant” Fungus, Ophiocordyceps unilateralis (FFF#006).

A note on the title “truffle”: Underground mushrooms that are dispersed by being dug up and eaten by animals have evolved many times. For Fungus Fact Friday, I opted to differentiate between “truffles” and “false truffles” based on phylum: truffles are ascomycetes while false truffles are basidiomycetes. Using my definition, Elaphomyces counts as a truffle. However, many authors do not follow this convention and there is considerable disagreement over how to define those terms. For some, false truffles are any truffle-like mushroom outside the genus Tuber. In this case, Elaphomyces is labeled a false truffle even though it is an ascomycete. To complicate matters a bit more, E. granulatus can be called “the false truffle” because it is the most common species of Elaphomyces.⁶ Others take the opposite position, applying the term truffle to everything that looks like a truffle. Following this method, Elaphomyces species are true truffles.