Harpidium gavilaniae is a little-known species of saxicolous (rock-dwelling), crustose lichen in the family Harpidiaceae. It is found in the Northern Cape Province in South Africa.
The lichen was formally described as new to science in 2011 by Guillermo Amo de Paz, Sergio Pérez-Ortega, and Ana Crespo. The type collection was collected east of Springbok in Namaqualand (Northern Cape province) at an elevation of . There it was found growing on quartzite in vertical furrows that are seasonally inundated with water. The species epithet honours the Spanish botanist Rosario Gavilán, who accompanied the authors during their fieldwork in South Africa.
The lichen species Harpidium gavilaniae has a crustose, thallus that can be rounded or ellipsoid and spans up to 2.5 cm in diameter. The , which are the small, distinct patches of the thallus, are independent and vary in shape from flat to (blister-like) or nearly stalk-like. These areoles are typically adhered to the substrate over most of their lower surface, with the peripheral zone often free and with a maroon-purple to copper-red colour. The peripheral areoles extend outwards, forming that are about 0.4âÂÂ0.9 mm wide, sometimes reaching up to 1.3 mm. In contrast, the central areoles are more rounded and typically bear immersed apothecia, measuring 0.3âÂÂ0.6 mm in diameter.
Structurally, the areoles are layered, with heights ranging from 0.2 to 0.7 mm. The tissue of the upper cortex is (made of hyphae are oriented in all directions) and is approximately 25 üm high. Below this, the , consisting of Trebouxia-like (spherical green algae) cells measuring 6âÂÂ15 üm in diameter, is continuous and spans 90âÂÂ200 üm in height.
The apothecia of Harpidium gavilaniae are irregularly rounded, typically one per areole, and immersed in the thallus, resembling those found in Aspicilia species. The apothecial are blackish, with diameters ranging from 0.1 to 0.4 mm. Surrounding the discs, the is up to 20 üm thick. The is reddish, does not react to potassium hydroxide (KâÂÂ), and is about 10 üm thick. The hymenium stands 50âÂÂ70 üm tall and turns blue when exposed to iodine (KI+). The are (resembling a string of beads), measuring 4âÂÂ6 üm wide and slightly wider at the apex.
The asci are - and in shape, each containing eight spores and measuring 24âÂÂ27 by 11âÂÂ14 üm. The ascus walls are thick. are hyaline and , with a crescent form where the two apices are rotated at a 90-degree angle, measuring 9âÂÂ13 by 6âÂÂ7 üm with thick walls (approximately 0.8 üm).
Pycnidia are frequently present, laminal, and immersed, measuring 70âÂÂ120 üm in diameter. The conidia are cylindrical to ellipsoidal, sized at 3 by 1 üm. No secondary metabolites were detected in Harpidium gavilaniae through thin-layer chromatography analysis.