SafePlants

River Jelly Lichen (Collema dichotomum)

The River Jelly Lichen, scientifically known as Collema dichotomum, is a fascinating lichen species that resembles seaweed more than a typical plant. It's also known by its common name, River Jelly Lichen.

Taxonomy and Nomenclature

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

Distribution and Habitat

• This aquatic lichen thrives on submerged rocks and boulders in fast-flowing rivers.
• It is known to be found in the upper reaches of rivers in Northumberland, England.
• The populations of river jelly lichen are thought to be the largest in Great Britain.

Morphological Characteristics

• The thallus (lichen body) forms flattened or erect rosettes that range in color from bright to dark green.
• When wet, the thallus is gelatinous and black.
• The thallus features broadly rounded lobes.
• Spores are 4-septate, hyaline, and measure 20-40 by 3-4.5.

Ecological Role

• It is crucial to ensure that activities like canoe access do not adversely affect populations of this lichen.
• Conservation efforts are in place to safeguard existing populations against developments that might compromise their survival.

Interactions with Other Organisms

• The photobiont (photosynthetic partner) of this lichen is the cyanobacterium genus Nostoc. This is what makes it a jelly lichen!