Fissurina astroisidiata
Fissurina astroisidiata is a species of lichen in the family Graphidaceae. Found in Veracruz, Mexico, it was described as new to science in 2011. This lichen was the first member of its genus discovered to produce cylindrical vegetative propagules called isidia, which help it spread vegetatively without sexual reproduction. It forms pale greyish-green crusts on tree bark in shaded rainforest and produces distinctive star-shaped reproductive structures.
Taxonomy
Fissurina astroisidiata was described in 2011 by María Herrera-Campos and Robert Lücking from material collected on the upper slopes of San Martin Tuxtla volcano in the Los Tuxtlas Biosphere Reserve, Veracruz, Mexico. The specific epithet combines the Latin astrum with isidiatus, alluding to the lichen's star-shaped and its coarse, cylindrical isidia—the first time true isidia have been recorded in the genus. A second isidiate species has since been discovered and described from China, Fissurina isidiata. Molecular data place F. astroisidiata at the base of Fissurina, close to F. dumastii and F. crassilabra. Morphologically it most closely resembles F. incrustans and F. karnatakensis, which share gaping lirellae with thin, pale labia, but both lack isidia and differ in ascospore size or chemistry.Description
The lichen forms a pale gray-green to olive-green crust up to 10 cm across and 100–150 micrometres thick. The thallus is cracked and noticeably bumpy; each bump often carries a tuft of stout, tapering isidia 1–2 mm long that darken at the tip as they age. In cross-section the thallus has a thin, cortex over an irregular peppered with clusters of calcium oxalate crystals.Reproductive structures are distinctive. The lirellae—elongate slits containing the asci—radiate from a central point on each bump, producing a star-like pattern 1–3 mm long. A complete surrounds each lirella, while the is partly exposed and the thin lips are yellow-white. Internally the is colorless to orange-brown, 15–25 μm thick; the hymenium stands 90–100 μm high and is clear, capped by a finely granular gray-brown. Each ascus contains eight ellipsoid spores that are somewhat and measure 12–15 × 6–8 μm, roughly twice as long as wide. No secondary metabolites have been detected by thin-layer chromatography.