Sarea difformis: A fungus that lives on conifer resin

**Black spruce resin with *Sarea difformis*.**

Conifer resin oozing from a tree is an inhospitable place. The terpenoid chemicals in resin are toxic to many forms of life, but not all. Even though conifer resins are full of anti-fungal and anti-bacterial compounds, some organisms have found a way around that. One of these is a fungus called Sarea, a genus of fungi that grows on the resins of pines, spruces, firs, and cedars. Organisms that live on resins are called resinicolous (resin plus “colous” meaning “inhabitant”).

From lichen to fungus

At one time, Sarea was thought to be a lichen, but because it lacks a photobiont (symbiotic photosynthetic organism), it has been “demoted” to a fungus. The tiny (barely 1 mm across) fungus bodies pictured above and below growing on the resin of a black spruce are, to the best of my knowledge, the apothecia (reproductive structures) of Sarea difformis. Cross-sections of the fruiting body examined under a microscope would make identification more certain, but that’s a bit out of my reach right now.

**A few small fruiting disks (marked by red arrows) of the fungus *Sarea difformis* are growing on the darker portions (are those part of the fungal body?) of the resin. Can you find more?**

I have looked for research papers on how Sarea can live on conifer resin, but the results have not yielded much information. Does it actually break down the resin components into simple carbohydrates? If so, then does it do this on its own, or is there a symbiotic relationship with bacteria or another fungus? Are the fungal hyphae growing in the resin or merely on top? How does it disperse? A lot of questions, and I’m sure there are answers somewhere.

Taxonomy

Sarea is a genus in the phylum Ascomycota (cup fungi, sac fungi), which includes familiar mushrooms like morels and the blue mold in Roquefort cheese. The taxonomy of the genus Sarea is not entirely settled, so some species may be moved to other genera, and species from other genera may be moved to Sarea. Also, new species are being discovered.

A similar resinicolous species that might be encountered in northern coniferous forests is Sarea (Zythia) resinae. It can be distinguished morphologically by the color of its apothecia. Sarea difformis has black apothecia, and Sarea resinae has orange apothecia.

Rare?

Sarea is not a rare fungus, but because of its small size and peculiar habitat, it is just rarely seen. It occurs throughout the cooler regions of the northern hemisphere.

Sources and additional reading

Coming attractions

I’m working on a few posts related to fungi and insects. One should be ready next weekend and will feature an unusual beetle that eats bracket fungi and sprays poison on its enemies. And a beautiful beetle, too, will be discussed. The fungi posts will be about some important species found across the northern boreal forests. There are still literature searches going on that lead me down many wandering paths, as well as coalescing all of this information into writing before these are ready to post.

Another fungus eating moth

***Metalectra quadrisignata (four-spotted fungus moth)*** **from Carlton County, Minnesota**

But not in Tineidae. This moth, Metalectra quadrisignata (four-spotted fungus moth), in the Family Erebidae, Subfamily Boletobiinae is yet another addition to the species checklist. The first syllables in the name Boletobiinae are “bolet” from “bolete” which is a name given to a vast group of species of mushrooms with large caps free from the stems and producing spores from pores, not gills. So, Metalectra quadrisignata is in the Subfamily Mushroom-iinae. Presumably, the larva of many or most of the members in this subfamily are fungivores but full life histories for species is incomplete. Larvae of Metalectra quadrisignata feed on bracket fungi preferring living or actively growing fruiting bodies. What species or even order is not specified. Some photos at Bug Guide show larva on a gilled mushroom and a slime mold which is not a fungus. It is unclear if they larvae were consuming these. I’ll need to start looking more carefully at these types of fungus.