Fissurina karnatakensis is a species of corticolous (bark-dwelling) script lichen in the family Graphidaceae. Found in India, it was formally described as a new species in 2007 by Urmila Makhija and Bharati Adawadkar. It grows on tree trunks in exposed conditions along roadsides within moist forests, particularly in Karnataka, a state known for its many endemic lichen species.
The thallus of Fissurina karnatakensis is brown and slightly glossy, with a smooth to uneven texture with cracks. The periphery of the thallus is delimited by a thin, black region. The ascomata, or fruiting bodies, are in form and immersed, matching the colour of the thallus. They can be simple or branched, measuring 1âÂÂ6 mm in length and 0.25 mm in width. The is not visible and very narrow, with a slit-like appearance. The is often separated by a narrow slit from the .
The exciple is non-striate and present at the base, with a pale orange-brown colour. It is non- and covered by a distinct layer. The hymenium, a layer containing the asci, is 105âÂÂ113 üm high. are approximately 1 üm thick, with hyaline, distinctly warty tips. are short to moderately long and distinctly warty. The asci are 8-spored, and the , which measure 14âÂÂ21 by 3âÂÂ5 üm with a 1âÂÂ1.6 üm-thick , contain 3 transverse septa.
Chemical spot tests reveal that Fissurina karnatakensis has K+ (yellow), CâÂÂ, KCâÂÂ, P+ (rust-red), and UVâ reactions. It contains protocetraric and fumarprotocetraric acids, which lichen products that are rare in the family Graphidaceae. Fissurina karnatakensis features the "comparilis-type" ascomatal structure and is distinct from other species like Fissurina verrucosa due to its exciple, which often has 2 striae (grooves), smaller ascospores (7âÂÂ12 üm long), and a thallus.