Sclerococcum gelidarium

Sclerococcum gelidarium
Scientific classification
Domain:	Eukaryota
Kingdom:	Fungi
Division:	Ascomycota
Class:	Eurotiomycetes
Order:	Sclerococcales
Family:	Dactylosporaceae
Genus:	Sclerococcum
Species:	S. gelidarium
Binomial name
Sclerococcum gelidarium Etayo & F.Berger 2000

Sclerococcum gelidarium is a species of lichenicolous fungus belonging to the family Dactylosporaceae. ^{[1] [2]} It has only been reported from Iceland. It grows on the host lichen Placopsis gelida , from which the species derives its epithet. ^[3]

Description

Sclerococcum gelidarium forms distinctive dark brownish-black, round, slightly convex reproductive structures (called sporodochia ) that measure about 250–300 micrometres (μm) in diameter. These structures develop on the surface of the host lichen. Each sporodochium consists of a pale-coloured base made up of densely packed cells arranged in a tissue-like pattern. From this base arise densely packed, unbranched, specialized fungal filaments (conidiophores) that are arranged in a palisade-like formation. These conidiophores measure about 50 μm in length and have grey to greyish-brown cells that appear swollen at the base. Only the cells at the tips of these conidiophores can produce spores. ^[3]

The spores (conidia) of Sclerococcum gelidarium are produced individually (a process known as monoblastic conidiogenesis) and arranged in chains. Each spore contains 2–5 cells (described as "phragmospore", which means a spore with cross-walls dividing it into several cells) and has an irregularly elliptical to irregular shape, measuring 8–12.5 by 6.5–8 μm. Young spores appear bluish-grey and are covered with small scale-like structures ( squamulae ). As the spores mature, they become brown, thick-walled, and heavily encrusted with a dark brown gelatinous material. The fungus spreads through the body (thallus) of its host lichen via microscopic filaments (mycelium). ^[3]

This species differs from the related Sclerococcum sphaerale by its bluish-grey to brown conidiophores and conidia, and by its spores that are encrusted with dark gelatinous scales. ^[3]

Habitat and distribution

Sclerococcum gelidarium is found growing parasymbiontically on the thallus (body) and cephalodia (specialized structures containing nitrogen-fixing cyanobacteria) of the lichen species Placopsis gelida . The species has a very limited known distribution, having been documented at only two locations in Iceland as of the time of is original description. ^[3]

References

1. "Sclerococcum gelidarium". Global Biodiversity Information Facility . Retrieved 5 June 2023.
2. "Sclerococcum gelidarium Etayo & F. Berger". Catalogue of Life . Species 2000: Leiden, the Netherlands. Retrieved 8 April 2025.
3. Berger, Franz (2000). "Beitrag zur Kenntnis der Flechten und lichenicolen Pilze Islands" [Contribution to the knowledge of lichens and lichenicolous fungi of Iceland](PDF). Acta Botanica Islandica (in German). 13: 69–82.