Heppia arenacea
Heppia arenacea is a species of terricolous lichen in the family Lichinaceae. Discovered in Yemen, it is characterized by its sand-coloured thallus and the incorporation of soil particles throughout its vegetative parts. The lichen is found in soil crust communities over limestone and basaltic rock in desert habitats, as well as in partially sheltered areas between large boulders.
Taxonomy
Heppia arenacea was first formally described by German lichenologist Matthias Schultz in 2005. The type specimen was collected by the author in Wadi Asariah, Jabal Arays at an elevation of approximately ; there it was found growing on exposed soil over basaltic rock under an Anisotes trisulcus shrub.Description
Heppia arenacea has a sand-coloured to pale ochre thallus, which can sometimes be slightly greyish-white and is somewhat gelatinous when wet. The thallus is, resembling an crust with somewhat angular to roundish measuring 0.6–2.5 mm wide.Microscopically, the lichen's thallus anatomy is, with an upper 20–35 μm thick, comprising cells that are angulate to roundish and small, measuring 3–5 μm wide. The is 75–150 μm thick, consisting of vertical or irregular reticulate hyphae, with short to elongated cells measuring 7.5–12.5 by 2.5–3 μm. The of Heppia arenacea is a filamentous cyanobacterium, present as short and contorted filaments or split individual cells. The filament cells are 7.5–12.5 μm wide without a sheath and 10–17.5 μm wide including the sheath. The lichen lacks a lower cortex and medulla. Except for the hymenium and, abundant soil particles are incorporated in all parts of the thallus and apothecium.