Fissurina nigrolabiata is a species of lichen-forming fungus in the family Graphidaceae. It was first discovered in 2011 in the mountain rainforests of the Philippines, where it grows as a thin greenish crust on tree bark. The species has since been found in Brazil, and produces its spores in distinctive black-lipped slits that protrude slightly from the bark surface.
Fissurina nigrolabiata was first described in 2011 from montane rainforest on Luzon, Philippines, by Eimy Rivas Plata, Patrick Bawingan and Robert Lücking. The species is based on material collected by Rivas Plata on Mount Palali (Nueva Vizcaya province) at an elevation of about 1,400 m in March 2007. The specimen, numbered 1198B, is preserved as the holotype in the Field Museum herbarium (F), with an isotype (duplicate) housed in the CAHUP herbarium in Los Baños.
In 2023 Pieter van den Boom, Harrie Sipman and Lücking published a second lichen from the Azores under the same binomial. Because the 2011 name already occupied the combination, the later usage is an illegitimate later homonym under Art. 53.1 of the International Code of Nomenclature for algae, fungi, and plants; taxonomic databases record it accordingly and a replacement name has yet to be proposed.
Fissurina nigrolabiata forms a thin, bark-dwelling (corticolous) crust up to about 5 cm across and only 30âÂÂ50 micrometres (üm) thick. Its surface is smooth to slightly uneven, glossy green, and protected by a narrow brick-like () cortex. Just beneath this skin lies an irregular layer of green algae along with conspicuous clusters of colourless crystalsâÂÂfeatures that give the thallus a subtly speckled look in thin section.
The reproductive structures are elongated slits called . These are straight to gently curved, seldom branched, and protrude slightly from the bark, measuring 1âÂÂ3 mm long and roughly 0.3âÂÂ0.4 mm wide and high. Each lirella is framed by a cream-coloured , but its lips () are thick, grey-black to brown-black, and capped by a thin translucent ; the itself remains hidden. Internally the entire âÂÂtissue surrounding the hymeniumâÂÂis heavily blackened (), reaching 200 üm thick beneath the hymenium. The colourless hymenium rises 120âÂÂ180 üm and contains eight spindle-shaped asci (80âÂÂ100 à15âÂÂ20 üm) per . Each ascus produces eight ellipsoid ascospores divided by several cross-walls (a arrangement), usually 12âÂÂ17 à5âÂÂ8 üm and about twice as long as broad. No secondary metabolites were detected by thin-layer chromatography, and the species lacks detectable asexual propagules.
Fissurina nigrolabiata is a corticolous (bark-dwelling) species and has been documented from the Philippines, and from Brazil.