Thallus areolate and usually placodioid, ±circular, 0.7–2 cm diam., or becoming confluent; areoles convex to bullate, 0.3–1 mm wide, but radially elongate at the thallus margin, forming convex lobes 0.25–1.4 mm long, greyish white or with a faint yellow-green tinge, matt; lobe tips sometimes slightly raised from the surface of the substratum, but ecorticate below; prothallus absent. In section: 200–300 µm thick or to 420 µm (or more) in old, bullate areoles; hyphae (2–)3(–3.5) µm wide, predominantly vertically orientated; cortex (phenocortex) 15–35 µm thick, hyaline; algal layer 60–110 µm thick; medulla I–. Photobiont cells 5–10 µm diam.
Apothecia at first plane and marginate, 0.3–0.5 mm diam., but later becoming convex with a reflexed margin, to 0.8(–1) mm diam. Exciple dark red-brown, c. 50 µm wide, but widening to c. 75 µm at the base; outermost edge usually with a narrow, hyaline zone to 8 µm wide containing free hyphal apices; hyphae radiating in a dense pigmented matrix, c. 2–2.5 µm wide, but outer 1–2 cells broader (3–4 µm) and free of pigment. Hymenium 75–85 (–100) µm tall, hyaline, I+ blue; epithecium purplish brown. Subymenium c. 30–50 um tall, dilute brown, composed of vertically arranged hyphae c. 2 µm wide and numerous ascogenous hyphae with hyphae to 7 µm wide. Hypothecium 60–145 µm tall, dark red-brown, with irregularly orientated hyphae, c. 2–2.5 µm wide in a densely pigmented matrix. Paraphyses simple or a few once-branched (especially in the upper part), 1.5–1.8 µm wide in mid-hymenium; apices incrassate to narrowly clavate, to 3.5 µm wide, wall colourless or pale purplish brown. Asci clavate, c. 70–75 × 15–23 µm, 4–8-spored; in K/I outer coat and tholus amyloid, but with a non-amyloid, triangular or cylindrical axial body. Ascospores variable in shape, fusiform, broadly fusiform (and then ± with an acuminate apex at one or both ends), ovoid-fusiform, ±cylindrical, or shortly acicular, (1–)3–7(–8)-septate, 20–36 × 3.5–6(–8) µm, without a perispore. All pigmented parts K+ purplish intensifying.
Pycnidia usually present but not abundant, visible as minute (50–60 µm diam.) sunken, red-brown pits in the surface of the areole. In section: seen to develop within the algal zone, ±ovoid, 90–115 µm wide but narrowing to 50–60 µm at the apex, 110–170 µm tall; wall hyaline, 5–7 µm wide, but wider and pale reddish brown around the ostiole. Conidiogenous layer convoluted into 2 (perhaps more) locules. Conidigenous cells slender, 9–12 × 1.5–1.7 µm. Conidia curved or hamate, aseptate, 10–11 × 0.8 µm.
Chemistry. Thallus K–, C–, KC–, P–, UV+ yellowish white; zeorin (major) and a chemosyndrome of 4 fatty acids - two of which appear to correspond with nephrosteranic and roccellaric acids by TLC. Nothing detected by HPLC.
Distribution and Ecology: So far known only from Campbell Island, where it grows on both calcareous and non-calcareous, sea-shore rocks. Associated taxa include species of Caloplaca, Collemopsidium and Verrucaria, suggesting that it grows in the mesic-supralittoral or lower xeric-supralittoral zones. Other collections from the same localities include Caloplaca regalis, Dirina neozelandica, Lecanora capistrata, Lecidea lygomma, Pertusaria erubescens, P. graphica, Tephromela atra, Turgidosculum complicatulum and Verrucaria mucosa.
Notes: The specimen packets were annotated “Toninia bacidioides” by Imshaug, suggesting that he was undecided whether to place this species in Bacidia or in Toninia. We have the same dilemma, and the possibility of describing a new genus to accommodate this remarkable species has also been considered.
In spite of the thallus colour and reaction under UV light, no xanthones, or any other substances, were detected by HPLC. This may indicate that the thallus colour is due to carotenoids as these do not tend to survive the highly acidic medium used for HPLC (J. Elix pers. comm.)
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