| Relicina | |
|---|---|
 | |
| Relicina eximbricata , in Florida | |
Scientific classification  | |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Lecanoromycetes |
| Order: | Lecanorales |
| Family: | Parmeliaceae |
| Genus: | Relicina (Hale & Kurok.) Hale (1974) |
| Type species | |
| Relicina eumorpha (Hepp) Hale (1974) | |
| Synonyms [1] | |
Relicina is a genus of foliose lichens belonging to the large family Parmeliaceae. It contains 60 species. [2]
Relicina was originally conceived as a series of the large genus Parmelia by lichenologists Mason Hale and Syo Kurokawa in 1964. A decade later, they promoted it to the status of genus. [3]
The genus Relicinopsis, proposed by Australian lichenologists John Elix and Doug Verdon in 1986 as a segregate of Pseudoparmelia , [4] was shown to be nested within Relicina in a 2017 molecular phylogenetics study. [5]
Relicina lichens have a leaf-like (foliose) body (thallus) with flat, two-sided lobes that are typically attached by a somewhat swollen, bulbous base. The edge of each lobe is lined with short, black, hair-like structures called cilia . The upper surface is generally yellow to yellow-green and may sometimes show small spots; it lacks the typical hairs and minute pores (pseudocyphellae) seen in some other lichens. Instead, the surface is covered by a continuous, pored layer (the epicortex ). On the underside, the color ranges from pale brown to black, and it bears simple or branched, root-like structures (rhizines) that extend to the edges, helping secure the lichen to its substrate. [6]
The lichen's photosynthetic partner is a green alga similar to those in the genus Trebouxia . Reproduction occurs through apothecia, which are open, disc-like fruiting bodies located on the surface of the lobes. These apothecia have a margin that resembles the thallus (a condition described as lecanorine ) and display a solid, uninterrupted disc that ranges in color from pale to dark red-brown. The disc lacks a powdery coating ( epruinose ) and is surrounded by a cup-shaped layer. The thallus-like margin is smooth or slightly scalloped and is often fringed with cilia at its base; in some cases, this edge appears almost crown-like due to the influence of swollen and bulbous pycnidia. [6]
Inside the apothecia, delicate filament-like cells called paraphyses are present; these are about 2–3 μm thick, mostly straight, and only lightly branched, with their tips being brown, rounded, and slightly expanded. The spore-bearing sacs, or asci, typically contain eight spores each. Each ascus features a well-developed, iodine-reactive (amyloid) zone known as the tholus that is pierced by a narrow, non-reactive central strand with parallel sides; there is no distinct ocular chamber. The resulting sexual spores are simple in structure, translucent (hyaline), ellipsoid in shape, and have walls about 0.5 μm thick. [6]
In addition to these sexual structures, Relicina produces asexual fruiting bodies known as pycnidia. These are embedded in the lichen's surface ( laminal and immersed ) and often appear somewhat swollen. They release conidia—small, asexual spores—that can be spindle-shaped ( bifusiform ) or more uniformly cylindrical to fusiform . [6]
Chemically, members of the genus Relicina contain usnic acid along with various other secondary metabolites such as depsidones, depsides, or fatty acids. [6]