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River Jelly Lichen: A Fascinating Aquatic Lichen

The River Jelly Lichen, scientifically known as Collema dichotomum, is a unique and intriguing lichen species. Its common name aptly describes its gelatinous texture and preference for aquatic environments.

Considerations for Pets

• The River Jelly Lichen, when wet, has a gelatinous texture.

Considerations for Children

• The River Jelly Lichen, when wet, has a gelatinous texture.

Taxonomy and Nomenclature

• Scientific Name: Collema dichotomum (With.) Coppins & Laundon
• Common Name: River Jelly Lichen
• Family: Collemataceae
• Order: Lecanorales
• Taxon Version Key: NBNSYS0000018437
• Synonyms: While not explicitly stated, the text suggests ongoing revision of generic boundaries within the Collemataceae, implying potential future name changes or reclassifications.

Description and Morphology

• The thallus (lichen body) forms flattened or erect rosettes, ranging in color from bright to dark green.
• It looks more like a seaweed than a typical lichen.
• The lichen features convex, finger-like lobes, typically one to two centimeters long.
• When wet, it becomes black and gelatinous.
• The thallus can grow to 2-4 cm broad.
• Spores are 4-septate, hyaline, and measure 20-40 by 3-4.5 micrometers.

Habitat and Distribution

• This aquatic lichen grows on submerged rocks and boulders in fast-flowing rivers.
• It has been found in the upper reaches of rivers in Northumberland.
• The populations in Great Britain of River Jelly Lichen are thought to be the largest.

Ecology and Symbiosis

• The photobiont (the photosynthetic partner in the lichen symbiosis) is a cyanobacterium of the genus Nostoc.
• Collemataceae (&#8220jelly lichens&#8221) is a large family of fungi forming lichen symbiotic relationships.

Quirky Facts

• Due to its gelatinous nature when wet, the River Jelly Lichen is sometimes mistaken for seaweed.
• The populations in Great Britain of River Jelly Lichen are thought to be the largest.
• Other jelly lichens listed include: Collema fasciculare, Collema crispum, Collema auriforme, Collema flaccidum, Collema fragile, Collema multipartitum, Collema furfuraceum

Further Information

• ARKive (for photos and facts)
• Encyclopedia of Life (for summaries)
• Partnership with Nature: A Local Biodiversity Action Plan for Wales.