Biatora species are
crustose lichens with a spreading ()
thallus that may appear thin and somewhat membranous in places. The surface is often cracked () and, in species that grow in association with
mosses, may be or warted. The thallus is typically creamy white, dull green,
glaucous green, or green-grey and lacks a distinct outer protective layer (). Some species produce
soredia, small reproductive that facilitate dispersal. A , the initial fungal layer that some lichens form before developing a full thallus, is absent. The
photosynthetic partner () is a alga, a group characterized by spherical to broadly
ellipsoidal cells. The reproductive structures (
apothecia) are , meaning they lack a derived from the lichen thallus itself. They are or closely to the surface and range from weakly to strongly convex. In some species, the apothecia are initially flat with a shallow margin but later become (without a distinct border). Their colour varies widely, including light beige, dark reddish brown, green-grey, bluish green, or khaki. Black apothecia are rare but, when present, have a green or blue tint when wet. Most species lack , the powdery surface coating found on some lichens. A well-developed (the outer tissue of the apothecium) is present but becomes reflexed over time. It consists of tightly packed, radiating
hyphae embedded in a gel matrix that remains stable in
potassium hydroxide (K) solution and does not swell. The outer edge may be coated with a thin gel layer. The
hymenium, where spores develop, is 30–100 μm tall and typically lacks a distinct (uppermost layer), though some species show pale pigmentation at the top. It does not contain granules or oil droplets and reacts with
iodine (I+),
staining red-brown when young and blue in older
herbarium specimens. Below the hymenium, the is distinct and slightly opaque due to the presence of ascogenous hyphae (spore-producing structures). The , a supporting tissue beneath the hymenium, consists of interwoven hyphae embedded in a dense gel matrix. The
paraphyses, sterile filamentous structures within the hymenium, are coherent in KOH, have narrow (0.5–2.5 μm wide), and are mostly unbranched, though occasional branching or connections (
anastomoses) occur. The tips of the paraphyses are slightly swollen, sometimes reaching up to 5 μm in diameter, and rarely bear a distinct cap or hood. The asci, where spores develop, contain eight spores and have a
Biatora-type structure. They feature a blue-staining (K/I+) apical dome penetrated from below by a non-staining (K/I–) apical cushion, which is surrounded by a deeply blue-staining zone. The ascus walls themselves do not stain in K/I but are surrounded by an outer layer that reacts red-brown in iodine (I+) and blue in K/I. The ocular chamber, an internal structure within the ascus, is relatively small. The are colourless, with a shape ranging from ellipsoidal to (thread-like) or (spindle-shaped). They may be aseptate (lacking internal divisions) or have between one and seven
septa. The spores are smooth and do not possess a distinct outer coating ().
Asexual reproduction occurs via
conidia, which are produced in small, flask-shaped reproductive structures called
pycnidia. These structures are within the thallus and have an unpigmented or weakly pigmented wall, similar in colour to the hymenium. The conidia themselves are colourless, aseptate, and (rod-shaped). Chemically,
Biatora lichens can contain a variety of
secondary metabolites, including
gyrophoric acid and
argopsin, and less commonly, other
depsides,
depsidones,
xanthones, or
usnic acid. Some species, however, lack detectable secondary metabolites when analysed using
thin-layer chromatography. ==Species==