Chapsa psoromica Cáceres, Santos de Jesus & Santos Vieira
Mycobank MB 517751
Thallus corticolous, up to 5 cm diam., 70–100 µm thick, continuous; surface smooth to uneven, olive-green. Thallus in section with well-developed, prosoplectenchymatous upper cortex with internal splitting and irregular algal layer; clusters of calcium oxalate crystals absent. Apothecia erumpent, angular-rounded, 0.4–0.6 mm diam.; disc more or less covered by a narrow pore, flesh-colored and slightly translucent, non-pruinose; proper margin indistinct; thalline margin fissured to lobulate with 3–6 inclined to erect lobules. Columella absent. Excipulum paraplectenchymatous, 30–60 µm thick, yellow; periphysoids present but indistinct. Hymenium 150–200 µm high, strongly inspersed and appearing nubilous grey; inspersion of two types: primary inspersion quickly dissolving in KOH and then hymenium appearing translucent, but secondary inspersion persistent; paraphyses unbranched. Ascospores 8 per ascus, 9–11-septate, 35–45 x 9–12 µm, oblong, with thickened septa and lenticular lumina, colourless, I+ dark violet-blue. Secondary chemistry: psoromic acid.
Chapsa psoromica at first glance resembles a species of Fissurina because of its olive-green, corticate thallus with a split-cortex and fissured apothecia. However, the apothecia are rounded with a well-developed disc and therefore the species is here placed in Chapsa. Inspersion is very rare in Chapsa and only two species with hyaline, transversely septate ascospores show this feature: C. elabens (Müll. Arg.) Rivas Plata & Mangold and C. pseudoschizostoma (Hale) Sipman (Rivas Plata et al., 2010). The latter has an ecorticate, whitish thallus and much smaller ascospores; also, the apothecia are pseudocolumellate. Chapsa elabens differs from C. psoromica in the ecorticate, endoperidermal thallus and the non-amyloid, narrower ascospores with more numerous septa. Both species also lack psoromic acid. Chapsa psoromica resembles other fissurinoid species in the genus, namely C. dissuta (Hale) Mangold, C. lassae Mangold, and C. zahlbruckneri (Redinger) A. Frisch. The first two are externally almost indistinguishable but have a non-inspersed hymenium and much smaller, 3-septate ascospores, and lack psoromic acid. The latter agrees with C. psoromica especially in the indistinct periphysoids, but its hymenium is also non-inspersed and the ascospores are muriform; in addition, the apothecia are much larger and more distinctly chroodiscoid; also here, psoromic acid is lacking. The unusual psoromic acid chemistry may suggests that C. psoromica is not a genuine Chapsa; however, in the related genus Thelotrema, there is also a single species with psoromic acid, T. saxicola (Vain.) Salis. (Rivas Plata et al., 2010).
The epithet refers to the unusual chemistry for this genus.
This species is thus far only known from the type collection from the state of Rondônia in the western part of the Amazon forest. It appears to be a forest understory species on the bark of large trees.
Type:—BRAZIL: Rondônia: Porto Velho, Estação Ecológica de Cuniã; 8º04’S, 63º31’W, 100 m; Jul 2009, Cáceres 7595 (holotype ASE; isotype F).
Additional specimens examined (paratypes):—None.
Sicut Chapsa elabens sed thallo olivaceo corticato, acidum psoromicum continente et ascosporis I+ violaceis differt.