Description
Austroroccella gayana presents as a pendent , bush-like (fruticose) lichen whose cords drape 5–40 cm down seaside rocks. Most branches are cylindrical, but many widen into thin, shovel-shaped blades that give the thallus a pliable, waxy feel. The surface is smooth and never wears the talc-like frost ( pruina ) that coats related genera; instead it shows sober grey-brown tones that darken toward the branch tips. Chemically the lichen is equally restrained: routine spot tests with potassium hydroxide (K), bleach (C) or para-phenylenediamine (PD) yield no colour change, and thin-layer chromatography detects only roccellic acid, whereas the erythrin and lecanoric acids that are found in many Roccella relatives are entirely absent. [4]
A thin cortex of vertically oriented, brown-tipped hyphae encloses a loose white medulla, while the basal holdfast turns coal-black as the hyphae compact against the rock. The internal partner is the green alga Trentepohlia , whose orange cells form a continuous layer just beneath the cortex. Reproduction is profuse: minute, disc-shaped apothecia stud the older branches in rows, their epruinose black discs bordered by a low collar of the thallus. Each fruit body shelters a 100 μm-thick hymenium threaded with delicate paraphysoids ; the asci discharge eight colourless ascospores that are spindle-shaped, divided by three cross-walls, and measure about 28 × 3 μm. Tiny pycnidia, seen as darker pin-pricks in the cortex, release thread-like conidia (12–16 × 1 μm) that provide an auxiliary means of dispersal. [4]
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