Tremella mesenterica vs Naematelia aurantia

Tremella mesenterica surrounded by its common host Peniophora quercina

Mostly during winter, gelatinous fungi of yellowish to slightly orange colour can easily be found growing out of dead (or dying) wood. Even though they all look morphologically more or less the same, there are two distinct species in Europe: Tremella mesenterica and Naematelia aurantia.

Fortunately, no microscopy is needed to identify them, but you will have to look carefully at the dead wood they are growing on and check if you find their host organism. Because yes, even though those fungi grow on dead wood, they do not consume the wood, they consume another fungus. And that fungus can either have corticoid fruiting bodies, often greyish-brown, pale or purple in colour, and belong to genus Peniophora, or it can have effuso-reflexed fruiting bodies, often yellowish in colour, and belong to genus Stereum (as far as I know, it is always Stereum hirsutum).

In short (you'll find an observation attached to this journal entry for every one of those three cases):

• If the fungus is found next to Peniophora sp, it can be identified as Tremella mesenterica.
• If the fungus is found next to Stereum sp, it can be identified as Naematelia aurantia.
• If neither or both are found on the same piece of wood, the fungus can only be identified as belonging to order Tremellales.

Even though many people ID those fungi as T. mesenterica if Stereum sp. is not visible on the photograph, you really should NOT do this... with one possible excpetion: On very thin, long twigs not or only very distantly connected to thicker branches, T. mesenterica can be inferred, because those are a good habitat for Peniophora sp. but not for Stereum sp. In this case you may ID to species lvl without a visible host. Generally, T. mesenterica will look a bit more glossy and transparent than the rather dull N. aurantia, but this should only be used as a supportive criterion to your ID, especially because, at least in my opinion, it is sometimes difficult to tell if something is glossy or humid or if it's just the lighting.

So please, if you want your observation of a yellowish, gelatinous fungi growing on dead (or dying) wood to count, provide a picture of that fungi together with its host. Look for it on the piece of wood you're photographing, especially on the side opposing the fungus. More often than not you will be able to spot the host after a short search. Please also take a look at the observation of N. aurantia linked below. You'll see that it would've been really easy to overlook the host, if I hadn't looked for it carefully, and you'll also see that if I hadn't, following the rule of thumb "No Stereum visible: T. mesenterica it is" would have let to a misidentification of the specimen. In a comment to this journal entry you will find some more N. aurantia observations that could have been (or have been) esily misidentified as T. mesenterica.

If you have valuable information to add, please do so in the comment section. Just because I'm writing this journal entry doesn't mean I'm the leading expert on those fungi.

Primary literature:

• https://www.sciencedirect.com/science/article/pii/S0269915X0980270X

Posted on January 24, 2024 05:33 PM by mangoblatt