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Lichen: Acarospora impressula

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Name: Acarospora impressula Th.Fr.

Pronunciation: Acarospora impressula

Conservation Evaluation: Least Concern

Acarospora impressula often runs along cracks and around large crystals in silica rich rocks. It has the overall appearance of dried snakeskin. Photographed in Cork Harbour. © Paul Whelan

Acarospora impressula often runs along cracks and around large crystals in silica rich rocks. It has the overall appearance of dried snakeskin. Photographed in Cork Harbour. © Paul Whelan

Body Type: Crustose

Description: The thallus forms small patches or areoles that are tightly interlocking and angular. The areoles are smaller near the edge of the thallus; colour is in the range of red-brown to dark-brown. The apothecia are concave, dark in colour; there tends to be just one per areole (check against Acarospora fuscata). The discs show a great variation in shape from angular to circular with a colour similar to the thallus. The areoles are small reaching a maximum size of just 2mm and the apothecia on them reach a maximum diameter of 0.5 mm. The overall appearance to the eye is that of dry snakeskin.

Acarospora impressula on a silica rich rock. © Paul Whelan

Acarospora impressula on a silica rich rock. © Paul Whelan

Chemical Tests: All Negative.

Nature Notes: A rather rare lichen in Ireland and confined to exposed rocky coastal regions formed from rocks with a high silica content. Seems to show a preference for sunlit granite where it grows among feldspar and quartz crystals. Do not confuse with Acarospora fuscata. Note the distribution map shows it near areas dominated by granite geology such as the Mourne Mountains, Dublin-Wicklow Mountains and Donegal. The southern and south western distribution tends to be along the coastal exposed Old Red Sandstone high in silica. While its presence in the Burren may initially seem rather odd, it has been recorded on some of the large granitic erratics that were left on the limestone paving after the last Ice Age.

Vice County distribution map of Acarospora impressula: See Map

Acarospora impressula

Acarospora impressula

Link: Map this species on the Lichen Survey

Other Acarospora recorded in Ireland

  • Acarospora benedarensis
  • Acarospora fuscata (Schrad.) Th.Fr.
  • Acarospora glaucocarpa (Ach.) Körb.
  • Acarospora heppii (Nägeli ex Hepp) Nägeli ex Körb.
  • Acarospora macrospora (Hepp) A.Massal. ex Bagl.
  • Acarospora rufescens (Ach.) Kremp.
  • Acarospora sinopica (Wahlenb.) Körb.
  • Acarospora smaragdula (Wahlenb.) A.Massal.
  • Acarospora veronensis Massal.

Text and images © Paul Whelan, 2009.