Chiodecton andamanicum Jagadeesh, 2014

Jagadeesh Ram, T. A. M., 2014, New species and new records in Roccellaceae (Arthoniales) from the Andaman Islands, India, Phytotaxa 177 (3), pp. 155-162 : 157-158

Chiodecton andamanicum Jagadeesh , sp. nov. (Figs 1C–D & 2I) MycoBank no.: MB809895

Chiodecton with perithecioid, solitary to united, lirelliform aggregated up to 180 µm diam. ascomata; white pruinose, 0.8–2(–2.5) × 0.8–1.2 mm stroma-like structures having more than 10 ascomata and lacking yellow pigment below the ascomata; I+ deep blue turns partly brownish red hymenium; thin, hyaline to pale brown hypothecium; hyaline, obovate-oblong, 4–5(–7)-septate, (18–)20– 25(–27) × (3.5–)4–5(–5.5) µm ascospores.

Type: — INDIA. Andaman Islands : South Andaman , Rani Jhansi Marine National Park , John Lawrence Island, Mangrove forest, on Rhizophora , elev. 5 m, 12 May 2012, T. A. M . Jagadeesh Ram 1980 (Holotype CAL) .

Thallus corticolous, epiphloeodal, up to 13 cm in diam., tightly attached, ± byssoid, minutely felty, smooth, becoming verrucose, whitish grey to greyish yellow, epruinose, ecorticate, 80–300 µm thick; prothallus distinct, pale brown to brown, 2–10 mm wide, byssoid, composed of radiating loosely interwoven smooth hyphae; medulla whitish, with few to many up to 20 µm wide calcium oxalate crystals; photobiont Trentepohlia , cells single or few cells aggregated, 10–18 × 9–12 µm. Ascomata perithecioid, solitary to united and lirelliform, aggregated into slightly elevated stromalike structures, 80–180 × 120–180 µm; stroma-like structures white pruinose, usually with more than 10 ascomata, 0.8–2(–2.5) × 0.8–1.2 mm, up to 0.6 mm high, ± constricted at base, lacking yellow pigment below the ascomata, I + orange and KI+ pale blue below the ascomata. Excipulum brown to dark brown, 6–10 µm thick. Hymenium hyaline, 80–110 µm high, not inspersed with oil droplets and granules, I + deep blue turns partly brownish red except the uppermost 15–30 µm which are persistently I + deep blue. Hypothecium thin, hyaline to pale brown, 5–12 µm thick, not forming a common dark brown carbonized hypothecium and extending to the substrate. Paraphysoids branched, 1 µm wide; tips slightly thickened, 1–2 µm wide. Asci clavate, 8-spored, 62–86 × 10–13 µm. Ascospores hyaline, obovate-oblong, 4–5(–7)-septate, (18–)20–25(–27) × (3.5–)4–5(–5.5) µm. Chemistry: Thallus K –, C –, KC–, P –, UV + grey white; I –, KI– (in section); roccellic acid (major) detected.

Notes: — Chiodecton andamanicum closely resembles Chiodecton applanatum G. Thor , a Malaysian species which also has similar stroma-like structures and the absence of common dark brown carbonized hypothecium extending to the substrate. However, it is distinct from Chiodecton applanatum G. Thor by the large stroma with over 10 much small ascomata, I + blue turns partly red hymenium and 4–5(–7)-septate much wider ascospores. The latter species has 5–10 ascomata per stroma, 0.4–7 mm wide ascomata, I + persistently blue, 3-septate, 22–31 × 2–3 µm ascospores. Chiodecton congestulum is the other similar species which shows similar hymenial I reaction but differs in having a common dark carbonized hypothecium ( Thor 1990, 2007).

Distribution and habitat: — Chiodecton andamanicum has been found in the type locality where it grows on the bark of the mangrove tree, Rhizophora . Etymology: —The specific epithet refers to its inventory from the Andaman Islands. Additional specimen examined: — INDIA. Andaman Islands: South Andaman, Rani Jhansi Marine National Park, John Lawrence Island, Mangrove forest, on Rhizophora , elev. 5 m, 12 May 2012, T.A.M. Jagadeesh Ram 2029 (PBL).

FIGURE 1. A. Bactrospora littoralis (holotype), part of thallus with apothecioid ascomata. B. B. medians (holotype), part of thallus with apothecioid ascomata. C–D. Chiodecton andamanicum (holotype). C. Part of thallus with prothallus. D. Stroma-like structures with perithecioid ascomata. E–F. Sagenidiopsis atroalba (holotype). E. Part of thallus with prothallus and apothecioid ascomata. F. Detail of thallus with ascomata. Scales: A–F= 1 mm.