Schizotrema
From Wikipedia, the free encyclopedia
| Schizotrema | |
|---|---|
Scientific classification  | |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Lecanoromycetes |
| Order: | Graphidales |
| Family: | Graphidaceae |
| Genus: | Schizotrema Mangold & Lumbsch (2009) |
| Type species | |
| Schizotrema zebrinum Mangold (2009) | |
| Species | |
|
S. flavolucens | |
Schizotrema is a genus of lichen-forming fungi in the family Graphidaceae. The genus was circumscribed in 2009 by Armin Mangold and H. Thorsten Lumbsch.[1]
The genus Schizotrema consists of lichens with a thallus that can range from being immersed in the substrate to appearing more superficial. The thallus is usually pale in colour and often inconspicuous. Its photosynthetic partner, or photobiont, is a green alga from the genus Trentepohlia. The prothallus, a structure that sometimes surrounds the edges of the lichen, is faint and brown, blending subtly with the substrate. Some species produce soralia, which are small, discrete, and punctiform (dot-like) structures that release powdery reproductive propagules for asexual reproduction.[2]
The ascomata, or sexual reproductive structures are generally rounded and embedded within the thallus. These structures are surrounded by a thick, layered thalline rim, which may flake away as the lichen ages. The true exciple, the tissue surrounding the spore-producing region, is dark brown to black and multilayered. It may or may not react with iodine at its base (amyloid or non-amyloid) and is lined with small hair-like structures known as periphysoids.[2]
Internally, the hymenium (spore-producing region) is tightly packed and does not react to iodine staining (non-amyloid). The hamathecium, the network of sterile filaments within the hymenium, is composed of unbranched paraphyses with tips that are not thickened. The asci, which are sac-like structures where spores develop, are clavate (club-shaped) and contain between one and eight spores. These asci also do not react to iodine. The spores produced by Schizotrema are transversely septate (divided by cross-walls) or muriform (divided into multiple compartments by both transverse and longitudinal walls). They are hyaline (colourless) to yellowish, sometimes becoming brown at full maturity, and may have a thin gelatinous coating. Asexual reproductive structures called conidiomata have not been observed to occur in this genus.[2] Secondary chemistry is variable: some species contain β-orcinol depsidones, while others appear to lack detectable lichen substances.[3]
