Roccellinastrum spongoideum (Follmann)

Jung, Patrick, Werner, Lina, Briegel-Williams, Laura, Emrich, Dina & Lakatos, Michael, 2023, Roccellinastrum, Cenozosia and Heterodermia: Ecology and phylogeny of fog lichens and their photobionts from the coastal Atacama Desert, MycoKeys 98, pp. 317-348 : 317

Roccellinastrum spongoideum (Follmann)

Fig. 1

Description.

Thallus usually 2 cm large but specimens up to 7 cm were observed, gray to brownish gray, sub- fruticose, byssoid-spongiose or cottony-granular. Lobes tubular, up to 20 mm long or longer, cylindrical and up to 5 mm broad or flattened and up to 6 mm broad, partly fenestrate in older parts. Young thalli at first as erect tufts developing to hollow tubes covered with white to light pink or brownish apothecia which are laminal, up to 0.5 mm broad, frequently compound, sessile or shortly stipitate. Hymenium 35-45 µm high, paraphyses branched, hypothecium colorless. Asci 26-35 × 8-10 µm, spores 1-septate at maturity, 7.5-10 × 1.5-3 µm. Excipulum of (often dichotomously) branched, radiating hyphae with strongly gelatinized walls, colorless, not sharply delimited from the paraphyses. Single hyphae often form loop structures in inner thallus parts. Thallus hyphae 3-9 µm wide, lumina ca. 1 µm thick. Cell lumina elongated or short, the ends sometimes characteristically enlarged adjacent to septa. Cells of the Symbiochloris photobionts (= ‘micareoid’) of 8-10 µm in diameter, arranged in nests of several cells.

Secondary metabolites.

Atranorin, protocetraric acid and traces of two unknown constituents. UV-, K-, C-, KC+ orange, P+ yellow to orange.

Distribution and ecology.

The endemic species grows epiphytically on downwards pointing needles mainly of the cactus Eulychnia sp. along the Coastal Range of the Atacama Desert of Chile where fog frequently occurs.

Notes.

The pale brownish tinge of the apothecia is caused by crystals of pigments deposited on the outer surface of the fruiting bodies. It seems that Follmann (1967) misinterpreted these crystals when he described a dark hypothecium and excipulum; in sections of the apothecium, hypothecium and excipulum are, in fact, colorless. R. spongoideum is easily distinguished from the other species by the well-developed grayish thallus composed of rather compact, tubular lobes, by the one-septate spores, and by its restricted habitat on cacti in fog zones along the coast of northern Chile.

Specimens examined.

specimen HBG-025791 (Herbarium Hamburgense, Hamburg, Germany) from Chile, Atacama Desert, Pan de Azúcar National Park.

Figures

Figure 1. Roccellinastrum spongoideum A, B photographs showing R. spongoideum on the downfacing cactus needles of different Eulychnia cacti in the National Park Pan de Azucar C photograph of byssoid lichen thallus D, E close-up of byssoid thallus showing the coarse hyphal structure F SEM image of hyphal loops G close-up of a cross section with a loose hyphal network, patchy arrangement of photobionts and pink apothecia H SEM image of four ' micareoid' photobionts on fungal hyphae I light microscopy of micareoid photobionts with large vacuole-like structures J, K SEM image and light microscopy of the lichen thallus L microscopic cross section through apothecium with two-celled spores divided by a septum. QR code redirects to 3 D scan of R. spongoideum. PW: Lichen.