Verrucula hladuniana (Nav.-Ros. & C. Roux) Nav.-Ros. & C. Roux

Parasitic lichen, specific of Caloplaca marina.

     Thallus rather small at first, 0.5-1.5 cm diam., made of polygonal areoles, 0,2-0,6 mm, greyish. Perithecia, 1-2 (3) per areole, 0.1-0.2 mm diam., faintly prominent, black. Ascospores narrowly ellipsoid, 12-16 x 5-7 µm. Pycnidia numerous. Conidia, 4-6 x 1 µm. Chemical spot tests negative. Parasite of Caloplaca marina, rather inconspicuous, visible to the naked eye, at first as blackish to dark grey spots on the thallus of hosts; later this species may become independant from the host, reaching bigger sizes (10-20 mm) owing to the confluence of several polygonal areoles, those of margin may be squamulose (see pictures) and in that case it resembles to Verrucula maritimaria Nav.-Ros. & C. Roux. This species is probably widespread, but so inconspicuous that it has to be specifically searched in its habitat, (see Navarro-Rosines, Roux et Gueidan 2007). It also seems thermophile but up to now it only has been  found in well-lit habitats exposed to the South in our prospection area. N.B. Placopyrenium fuscellum is rather similar but the latter has a larger size and, being parasite of  Verrucaria nigrescens, its habitat is different.*