Arthonia sanguinaria Frisch & Y. Ohmura, 2018

Frisch, Andreas, Grube, Martin, Kashiwadani, Hiroyuki & Ohmura, Yoshihito, 2018, Arthoniaceae with reddish, K + purple ascomata in Japan, Phytotaxa 356 (1), pp. 19-33 : 25-26

Arthonia sanguinaria Frisch & Y. Ohmura sp. nov.

MycoBank MB823125

Diagnose.—This species differs from the similar A. meissneri Müll. Arg. by the larger ascospores (15–21 × 5–8 μm, 4–5-septate vs 10–14 × 4.5–5.5 μm, 2-septate). Arthonia picea Vain. has thick-walled ascospores, 26–35 × 9–12 μm, turning brown with granular ornamentation in the perispore at late maturity, and a different chemistry (pigments A4, A5, A6). Arthonia ferruginea Vainio (1890: 165) has a distinct K+ blue pigment in the ascomata and slightly larger ascospores (20–24 × 5–8 μm, 5-septate).

Etymology.—The new species is named after the blood red colour of the ascomata.

Type.— Japan, Ogasawara Islands (Tôkyô Metropolis): Chichi-jima, Mt Tsutsuji (27°03′33.7″N, 142°13′15.6″E), on bark of Livistona chinensis var. boninensis , elev. 250 m. 28. vi. 2009, Y. Ohmura 6609 (TNS holotype). FIG. 3C, 3D , 4C

THALLUS pale olivish grey to pale buff(almost whitish),thin,matt, smooth to granular-warty, coherent to fissured-areolate, up to 0.1 mm tall, partly endophloeodal; prothallus line not observed; photobiont trentepohlioid, the cells rounded to elliptical, 6–18 × 4–8 μm, in short chains or single cells; mycobiont hyphae 1.5–2.5 μm wide, with thick (0.7–1.0 μm) walls, hyaline, weakly conglutinated; calcium oxalate crystals not observed. ASCOMATA dispersed, maculate, immersed, flat, irregularly rounded to elliptical to shortly lobed, 0.5–3.0 × 0.4–1.3 mm, often separated from the thallus by a thin fissure, margin not differentiated; disc dark red, flat, level with the thallus, epruinose; proper exciple not differentiated, the margins of the ascomata without asci and with more closely netted paraphysoids; epithecium deep orange, 7–12 μm tall; hymenium deep orange-red, 40–45 μm tall, strongly conglutinated, the asci distantly spaced; hypothecium brown to olive-brown, 15–25 μm tall, conglutinated, of short-celled, densely branched and netted prosoplectenchymatic hyphae (cells 2–5 × 0.7–1.0 μm); quinoid pigments mainly as amorphous pigmentation in the gelatinous matrix of epithecium, hymenium and hypothecium, and to a lesser degree as ca 1 μm wide granular crystals attached to the hyphal walls; paraphysoids densely branched and netted, 1.0–1.5 μm wide, somewhat wavy; paraphysoid tips only slightly widened to 1–2 μm, without pigmentation of the walls. ASCI of the Arthonia-type, with broadly triangular ocular chamber, 40– 48 × 20–24 μm (n=10), lateral walls 0.5–1.0 μm thick, base not abruptly deflected, 8-spored (spores in 2–3 irregular rows). ASCOSPORES narrow elliptical with capitate upper cell, (15.0–)16.8–19.4(21.0) × (5.0–)6.1–7.5(–8.0) μm (n=40; STDV: l=1.30, w=0.66), hyaline, 4–5-septate, slightly constricted at the septa, overaged collapsed spores with pale brownish walls lacking a clear granular ornamentation in the perispore. PYCNIDIA not observed.

Chemistry.— Confluentic acid (major), ± psoromic acid (minor), pigment A7 (major) in solvents B′ and C detected by TLC. Thallus hyphae I+ pale blue, KI+ blue; ascomatal gels I dil –, I+ blue, KI+ blue; asci with small KI+ blue ring structure in the tholus; ascospore walls and septa I–, KI–. The pigments change to purple in K but do not dissolve.

Ecology and distribution.— On the trunk of Livistona chinensis var. boninensis in dense humid forest. The species is known from a single locality on Chichi-jima in the Osagawara Islands.

Notes.— A distinctive species with almost whitish, pale olive grey thallus, dark red maculate apothecia, and hyaline, 4–5-septate ascospores with enlarged apical cell, 15–21 × 5–8 μm. The thallus margins show a distinct but rather weak zonation of brownish pigmentation. The pigments in the apothecia dissolve in LCB with precipitation of stellate clusters of red prism-shaped crystal needles ( Fig. 4B ), a character not observed in the other species treated in this study. A. meissneri Müll. Arg. (type: G!) is a fairly similar widespread species in the tropics. The ascospores of A. meissneri , however, are distinctly smaller (10–14 × 4.5–5.5 μm, 2-septate) and this species does not contain psoromic acid. Superficial similarities also exist with the neotropical A. ferruginea Vain. (TUR-Vain 28914!, holotype), but that species differs by a distinct K+ blue pigment in the ascomata and slightly larger ascospores (20–24 × 5–8 μm, 5- septate).

Additional specimen examined: — Japan, Ogasawara Islands (Tôkyô Metropolis): Chichi-jima, Mt Tsutsuji (27°03′33.7″N, 142°13′15.6″E), on bark of Livistona chinensis var. boninensis , elev. 250 m. 19. iii. 2013, A. Frisch 13/Jp59 (TNS).

Figures

FIGURE 3. Thallus and ascomata. A. Arthonia lopingensis on Graphis handelii (Frisch 12/Jp5, TNS). B. Coniocarpon cinnabarinum (Frisch 13/Jp128, TNS). C, D. Arthonia sanguinaria (Frisch 13/Jp59, TNS): A margin of thallus, B ascomata. E. Arthonia picea (Kashiwadani 14142, TNS). F. Arthonia eos (Thor 26000, GZU). Scale bars:A, B=0.5 mm, C, E, F=1 mm, D=1.5 mm.

FIGURE 4. Details of the ascomata. A. Arthonia lopingensis, Arthonia-type ascus and spores (Ohmura 9795, TNS). B. Arthonia sanguinaria, young spores and crystal needles formed in LCB (Ohmura 6609, holotype, TNS). C, D. Arthonia picea (Kashiwadani 14742, TNS), C Arthothelium-type ascus with young spores, D spores. Scale bars = 10 μm.