Cryptothecia rubrocincta is a species of lichen in the Arthoniaceae family of fungi. The species is prominent in Central Florida wilderness areas this month. It is distributed in subtropical and tropical locations throughout the southeastern United States, as well as Central and South America.
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Lichens exist in many forms, ranging from flat, smooth organisms to frilly species and those that resemble greenish Spanish moss (which is a flowering bromeliad and not a moss). In the image above the Christmas lichen is living in close proximity to the more common and abundant Cryptothecia striata (white-to-grey circular lichens).
Lichens are biologically interesting in that they are composed of symbiotic associations of fungi (called the mycobionts) and algae or cyanobacteria (the photobionts, the latter being blue-green algae). The fungus gives the organism its structure and a means of maintaining moisture, and the algae or cyanobacteria supply the fungus with nutrients.
Above and Below: These specimen are living adjacent to Bulbothrix laevigata (Eyelash Lichen) and Hyperphyscia pustulifera (Loop Lichen),
Lichen species are defined by the type of fungus, type of photobiont, and the shape the association assumes. Though some are distinct enough that they can be identified by their morphology, a student often has to apply certain chemicals to note color changes in order to distinguish among species.
The body of the lichen forms continuous, circular crust-like patches on dead wood, readily recognizable by the prominent red pigment. The older, central region is covered with red, spherical to cylindrical granules. Moving outwards from the center, zones of color may be distinguished, the first gray-green, the second white, and finally a bright red cottony rim. The red and green colors of this unmistakable woodland lichen give the appearance of a Christmas wreath, suggestive of its colloquial North American name, the Christmas wreath lichen.
“Rubrocincta” translates to “red wreath.” The central, oldest area of the thallus is often adorned by dense clusters of small red granules that look somewhat like isidia – one of the two types of reproductive methods employed by lichens.
The red pigment, called chiodectonic acid is one of several chemicals the lichen produces to help tolerate inhospitable growing conditions.
Cryptothecia rubrocincta is a crustose lichen, because it grows in the form of a surface crust. The thallus, or body of the lichen is spread out flat and can be either tightly to loosely attached to the growing surface. It is 0.15–0.30 mm thick, and can be smooth, or have low radiating ridges. The older, central region of the lichen surface has many reproductive structures called isidia; they resemble granules that are 0.1–0.4 by 0.1 mm.
The species relies entirely on vegetative means to reproduce, and is not known to have any sexual structures. From the center outwards, three color zones can be differentiated in mature specimens; the first grayish-green, the second white, and finally a bright red cottony rim.
All of these specimen were photographed within a 3 mile radius around the Florida Trail between the Black Hammock Wilderness Area (Lake Jesup) and the Little Big Econ State Forest (Econlockhatchee River) on the outskirts of Oviedo, Florida, an eastern suburb of Orlando.
These specimen were growing exclusively on hardwoods (live oak, hickory, magnolia, lyonia) and were found in thick hammocks mostly facing north or west away from the most punishing Florida sun and in areas that sometimes contain standing water.
Scientific description: The lichen has a distinct prothallus—fibers of whitish fungal hyphae at the edge that lack photobiont, and which project beyond the thallus onto the growing surface. The prothallus is red to whitish in the inner part, red the in outer part. The surface of the thallus does not have a well-defined cortex, an outer layer of well-packed hyphae. The medulla (a loosely arranged layer of hyphae below the cortex and photobiont zone) is whitish but the lower part is red. It has few to many calcium oxalate crystals that are 3–8 μm diameter. The hyphae of the medulla have many such crystals on the walls, that are 1–2 μm in diameter. The algal photobiont (technically a phycobiont, as it is a green algal photosynthetic partner) is from the genus Trentepohlia. Normally, the algae is long and filamentous; when in the lichen state, it is divided into shorter filaments. The alga has a large chloroplast that contains droplets of beta-carotene. The lichen is heteromerous, meaning that the mycobiont and photobiont components are in well-defined layers, with the photobiont in a more or less distinct zone between the upper cortex and the medulla. Cells are single or a few cells aggregated, with dimensions of about 8–15 by 5–11 μm.
The lichens geographical range extends northward as far as the extent of Sabal Palmettos, generally thought to be some of the southern islands of North Carolina.
As seen in many of these images Christmas lichen is often found with or alongside Cryptothecia striata (the white to grey round circular lichens). Cryptothecia striata is also an easily identified lichen with its white cottony prothallus and mint green thallus. A drop of ordinary household bleach on the surface produces a bright red color. This genus is unusual in that it bypasses the chore of producing fruiting bodies (apothecia or perethecia). Instead asci are apparently produced within the thallus and arise when mature.
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