Viridothelium sinuosogelatinosum

Viridothelium sinuosogelatinosum is a species of crustose lichen in the family Trypetheliaceae.^[1] This corticolous (tree bark-dwelling) lichen is characterised by its pale olivaceous-brown thallus and its unique ascospores, which are surrounded by a wavy gelatinous sheath. It was discovered in the Amazonas state of Brazil, within the Adolfo Ducke Forest Reserve near Manaus.^[2]

Viridothelium sinuosogelatinosum
Scientific classification
Kingdom:	Fungi
Division:	Ascomycota
Class:	Dothideomycetes
Order:	Trypetheliales
Family:	Trypetheliaceae
Genus:	Viridothelium
Species:	V. sinuosogelatinosum
Binomial name
Viridothelium sinuosogelatinosum Aptroot & M.Cáceres (2022)
Holotype: Adolfo Ducke Forest Reserve, Brazil

Taxonomy

Viridothelium sinuosogelatinosum was formally described in 2022 by the lichenologists André Aptroot and Marcela Eugenia Cáceres, as part of a broader study aimed at cataloging the lichen biodiversity within a small area of the Amazon rainforest. The species epithet, sinuosogelatinosum, alludes to the distinctive wavy (sinuoso) gelatinous sheath that envelops the ascospores, highlighting one of its most distinguishing features.^[2]

Description

The thallus of Viridothelium sinuosogelatinosum is crustose (crust-like), corticate, and has a dull pale olivaceous-brown colouration. It does not have a prothallus bordering it. The ascomata (fruiting bodies) are single, either globose or pear-shaped, measuring between 0.4 and 0.6 mm in diameter, and are black in colour. The ostioles are apical or slightly off-centre, dark brown with a pale dot in the centre, and concave.^[2]

The hamathecium (a tissue composed of filamentous hyphae) lacks any inspersed oil droplets. Ascospores are produced eight per ascus, are hyaline (transparent), and 3(–4)-septate. They measure 33–37 by 8–11 μm, and are long-ellipsoid in shape with rectangular lumina. Each spore is encased in a wavy gelatinous sheath up to 5 μm thick. No pycnidia (asexual fruiting bodies) have been observed to occur in this species.^[2]

Spot tests performed on the thallus show no reaction to ultraviolet light, and negative results for standard lichen substances reactions (C, K, KC, P).^[2]