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River Jelly Lichen (Collema dichotomum)

The River Jelly Lichen, scientifically known as Collema dichotomum, is a fascinating lichen species with a unique appearance and habitat.

Common Names

• River Jelly Lichen

Taxonomy and Nomenclature

• Scientific Name: Collema dichotomum (With.) Coppins &amp Laundon
• Family: Collemataceae
• Order: Lecanorales
• Synonyms: C. ohioense

Distribution and Habitat

• This aquatic lichen is found on submerged rocks and boulders in fast-flowing rivers.
• It has been observed in the upper reaches of rivers in Northumberland, Great Britain.

Morphological Characteristics

• The thallus (lichen body) forms flattened or erect rosettes, ranging in color from bright to dark green.
• It consists of convex, finger-like lobes typically one to two centimeters long.
• When wet, it has a gelatinous texture and looks more like seaweed than a typical lichen.
• The thallus can grow up to 2-4 cm broad, black, gelatinous when wet, with broadly rounded lobes isidia and soredia lacking spores 4-septate, hyaline, 20-40 by 3-4.5.

Ecology

• The photobiont (the photosynthetic partner in the lichen symbiosis) is the cyanobacterium genus Nostoc.
• It is one of the cyanobacteria-containing jelly lichens.

Quirky Facts

• Due to its gelatinous nature when wet, the River Jelly Lichen can resemble seaweed, a characteristic that distinguishes it from many other lichens.
• It absorbs water until it is jelly-like.

Further Information

• Learn more about the River Jelly Lichen on ARKive.
• Encyclopedia of Life has briefs summaries and articles about Collema dichotomum.