Cryptothecia rubrocincta

Appearance

''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.

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 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 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 yeast ''Fellomyces mexicanus'', an anamorphic member of the Cuniculitremaceae family, was discovered growing epiphytically on the lichen in 2005.

Naming

The classification of the genus ''Cryptothecia'' has been unclear, and historically, ''C. rubrocincta'' has been placed in several different genera. Like all lichens, ''C. rubrocincta'' is an association of a fungus with a photosynthetic organism , in this case, an algae. Initially, it was unknown whether the mycobiont component of ''C. rubrocincta'' was an ascomycete or a basidiomycete. Although the vast majority of lichen mycobionts are from the Ascomycota, in 1937 German lichenogist Friedrich Tobler believed the mycobiont to be a basidiomycete, because he interpreted some unusual microscopic structures to be clamp connections, structures associated only with the basidiomycete fungi. In another publication later that year, he specified the mycobiont to be a hymenomycete, and described the monotypic genus ''Herpothallion'' to supersede the old name ''Chiodecton sanguineum''. Although Vernon Ahmadjian corroborated the presence of clamp connections in the species when he studied the species' cytology in 1967, other researchers did not find clamp connections in specimens collected from different countries. Further doubt was cast on the possibility of a basidiomycete mycobiont with the discovery of the depside confluentic acid in 1966, concentric bodies in 1975, and woronin bodies in 1983, as all of these characteristics are restricted to Ascomycetes.

The International Code of Botanical Nomenclature states that names of fungi adopted by Fries in Systema Mycologicum vols. 1–3 are sanctioned, that is, they are conserved against earlier homonyms and competing synonyms. This means that the name ''Hypochnus rubrocinctum'' has priority over ''Byssus sanguinea''. The type material of ''H. rubrocinctum'' was examined by Christian Gottfried Ehrenberg in Berlin; it has since been destroyed, probably during the Second World War. The drawing in Erhenberg's 1820 publication serves as the lectotype. The species was transferred to the genus ''Cryptothecia'' by Swedish lichenologist Göran Thor in 1991, on the basis of its similarity with ''C. striata'' such as the thallus with radiate ridges, granular isidia, and presence of ''para''-depsides .

The red and green of ''C. rubrocincta'' give it a Christmas wreath look, hence its common North American name, the Christmas wreath lichen. The specific epithet is derived from the Latin words ''ruber'' "red" and ''cinctus'' "girdled/encircled" or "banded". The other epithet ''sanguineum'' is the neuter form of the Latin adjective ''sanguineus'' "bloody".

Distribution

The lichen is widely distributed in the southeastern United States; in 1954 the north border of its distribution was given as a line passing through southern Louisiana, Mississippi, Alabama and Georgia. Although the northern limit was extended to southern Delaware, the author later revised his opinion, and the northern limit is thought to be North Carolina. In North Carolina, it is found on Smith Island, a notable location because it represents the northern limit of the distribution of cabbage palmetto . The presence of this 6 meter tree interspersed among the dominant tree species ''Quercus virginiana'' give the island a subtropical appearance—consistent with the lichen's preferred climate.

''Cryptothecia rubrocincta'' is also widespread in tropical and subtropical areas of the West Indies and Central and South America. In South America it is found north of Chile and Argentina. It is rarer in Africa, having only been collected from three geographically widely separated mountain regions: São Tomé and Príncipe, Tanzania, and DR Congo. The lichen may be found at altitudes ranging from sea level to 2,600 metres .

The lichen typically grows on rough bark in sheltered and shaded habitats in moist and dense subtropical forests. More rarely, it is found on rocks or on leaves. In the USA it occurs in hammocks and swamps which have standing water, at least part of the year. It is also common in oak or oak-pine scrub vegetation. The species is often associated with ''Cryptothecia striata'' in the USA.

Habitat

The lichen is widely distributed in the southeastern United States; in 1954 the north border of its distribution was given as a line passing through southern Louisiana, Mississippi, Alabama and Georgia. Although the northern limit was extended to southern Delaware, the author later revised his opinion, and the northern limit is thought to be North Carolina. In North Carolina, it is found on Smith Island, a notable location because it represents the northern limit of the distribution of cabbage palmetto . The presence of this 6 meter tree interspersed among the dominant tree species ''Quercus virginiana'' give the island a subtropical appearance—consistent with the lichen's preferred climate.

''Cryptothecia rubrocincta'' is also widespread in tropical and subtropical areas of the West Indies and Central and South America. In South America it is found north of Chile and Argentina. It is rarer in Africa, having only been collected from three geographically widely separated mountain regions: São Tomé and Príncipe, Tanzania, and DR Congo. The lichen may be found at altitudes ranging from sea level to 2,600 metres .

The lichen typically grows on rough bark in sheltered and shaded habitats in moist and dense subtropical forests. More rarely, it is found on rocks or on leaves. In the USA it occurs in hammocks and swamps which have standing water, at least part of the year. It is also common in oak or oak-pine scrub vegetation. The species is often associated with ''Cryptothecia striata'' in the USA.