Lichen: Ochrolechia parella
Name: Ochrolechia parella (L.) A. Massal.
Pronunciation: Ochrolechia parella
Body Type: Crustose
Conservation Evaluation: Least Concern
Description: The thallus is white in colour. On close examination specimens can show a bluish tint to buff-white to grey colour. It forms regular circular or oblong growths where the substratum permits and when there is no competition from other lichens. Sometimes growth bands or zones can be distinguished in the thallus. The edge or prothallus is much whiter than the main body. Sometimes its growth pattern is irregular. The thallus is lumpy, particularly near the centre of a specimen.
The fruiting bodies or apothecia are abundant and have a margin the same colour as the thallus. When young or immature the apothecia are small and have a deeply convex disk. When mature they are quite large, 2 mm – 3 mm in diameter and in conjunction with the cracked and lumpy thallus give this crustose lichen a rough appearance. The margins of the mature apothecia are very thick and ridged. The apothecia disk is pale grey to pink. The disc itself is flat and frequently covered with a white frost-like coating of minute calcium oxalate crystals. Sometimes the margin of the disk is swollen like an over-inflated tyre and pushes in over the disk surface.
O. parella likes direct sunlight. The thallus is thick, prolific, lumpy and contains numerous apothecia in these conditions. When growing in the shade the thallus is thin with fewer reproductive structures and is often fringed or fimbriate at the edges. The apothecia are quite large, 2 mm to 4 mm in diameter, with thick rims. Spores are ellipsoidal. Sometimes the thallus and apothecia are heavily pruinose
Checmical Tests: C-, UV-, C+ red, KC+ red, UV+ white.
Nature Notes: This is probably Ireland’s most common white crustose coastal lichen. It is found in all coastal areas on smooth siliceous rocks. It favours slightly basic acid rocks such as basalt or gabbro. Gabbros are coarse grained basalts. In the sandstone hills of Kerry and West Cork, O. parella frequently forms large circular colonies. In 1915, the Irish lichenologist Matilda Knowles noted the regularity of a white lichen zone at the top of sea shores in the West of Ireland. She referred to this as the White Belt, with O. parella and Tephromela atra as characteristic species.
Although common around the coast, it is also found inland, particularly west of the river Shannon and in West Cork and Limerick. Ochrolechia parella grows mostly on rocks but can occasionally be found near the coast on trees such as sycamore, ash, rowan and elm.
Vice County distribution map of Acarospora fuscata: See Map
Link: Map this species on the Lichen Survey
Other species recorded In Ireland
- Ochrolechia androgyna (Hoffm.) Arnold
- Ochrolechia inversa (Nyl.) J.R.Laundon
- Ochrolechia microstictoides
- Ochrolechia subviridis (Hoeg) Erichsen
- Ochrolechia szatalaensis Verseghy 
- Ochrolechia tartarea (L.) A.Massal.
- Ochrolechia turneri (Sm.) Hasselrot
Text and images © Paul Whelan, 2009.