Nectria cinnabarina also known as the coral spot is a common species of flask fungus, distributed in colder environments. You will typically see this small fungus gregariously gathered on fallen branches in more northern latitudes. This species is also considered a weak wound parasite, as it tends to take full advantage of novel woody substrate when insects and other biota remove protective bark layers from trees. These miniature fruiting bodies are widely stepped over without being truly appreciated, so I thought I’d dedicate a Fungi Friday to this inconspicuous mycological wonder that has evolved some interesting physiology.
Over the past several months, I’ve talked about several fungal adaptations that enhance spore release. These strategies are quite diverse throughout this Kingdom, so it’s no surprise that I haven’t covered all of the fungal types. Members of the Ascomycetes are riddled throughout forest floor narrative’s articles, but the flask fungi associated with the class Sordariomycetes have taken a back seat. Until now.
Close up of Nectria cinnabarina perithecium. Photo by Amadej Trnkoczy.
The Sordariomycetes are a diverse class of fungi that contain 1344 genera. The species in this class display a wide array of fungal forms, but for the most part, they produce their asci (Ascomycete spore sac) in perithecial fruiting bodies. Perithecium are flask like structures with tiny openings or pores that allow ascospores to be released into the environment. This hardy structure protects the developing spores from the elements, reducing water loss during dry bouts that other unprotected species may succumb to. In most perithecial fruiting bodies, each ascus inside is phototrophic and has the ability to aim toward the tiny pore opening. In this species, when ascospores are completing their development, they migrate up the walls of the perithecium. As proper conditions become present, the ascospores are forcefully ejected from the tip of the ascus towards the pore opening. If all goes as planned, these spores will hopefully land on a fresh beech or sycamore tree wound, where they can carry out their life cycle again.
When you find this species this mushrooming season, you will note that there are slightly larger, different colored, soft tissue globules growing on the same twig or branch. Before Nectria cinnabarina was fully understood, these separate structures were described as another species; Tubercularia vulgaris. As it turns out that these paler, light pink or faint orange structures are the asexual form of this species, while the hardy perithecial fruiting bodies represent its sexual form. The asexual pustules consist of a dense tuft of conidiophores termed the conidial stroma .
Nectria cinnabarina. (a) Perithecium containing several asci. (b) Asexual conidial stroma. (c) Asci. (d) Conidiophore and conidia.
A recent 2011 study looked into the genomics of this species and isolated DNA from N. cinnabarina found in Asia, Europe, and North America. Along with DNA analysis, morphological examination of the ascus was too carried out. Different ascospore morphology was recognized from geographical separated specimens. What these researchers concluded was that N. cinnabarina is actually a species complex made up of 4 separate species.
The forest floor is teaming with diversity, but it can also be quite deceptive. The asexual form of Nectria cinnabarina is not the first-time mycologists falsely described a new species. It’s funny to me that initially, a new species was described only to be removed once realized it was just an asexual form. After that, 3 more species were described upon morphological and genetic analyses. Some predict that we have only described a fraction of Earth’s fungal diversity, and the story of N. cinnabarina definitely supports that theory.