Constrictolumina esenbeckiana

Constrictolumina esenbeckiana has a thin, whitish thallus. Its fruiting bodies (ascomata) are solitary, 0.4–0.6 mm in diameter, and range from partly immersed to distinctly raised above the surface. They are hemispherical to somewhat flattened, with apical openings, and frequently occur in dense groups of 5–20, where they may fuse sideways. The ascomatal wall is absent on the underside.^[5]

The asci are usually narrowly obovate, sometimes nearly cylindrical, and measure about 100–125 by 17–22 micrometres (μm). Each ascus contains 4–8 ascospores, arranged in two rows, overlapping rows, or nearly in a single line. The ascospores are narrowly egg-shaped, divided by a single cross-wall, and the lower cell may occasionally show a slight constriction. They measure 22–27 by 7–10 μm, with a well-developed outer layer (perispore).^[5]

Asexual reproductive structures (pycnidia) are often present, producing rod-shaped conidia about 4–5 by 1 μm. Both the thallus and ascomata test negative in standard chemical spot tests (UV and K), and thin-layer chromatography has not detected any secondary metabolites.^[5]

Constrictolumina esenbeckiana is a neotropical species known from the Antilles and Brazil. Most records are historical, but the lichen has also been documented more recently in Sergipe state, Brazil. It typically grows on bark in tropical habitats.^[5]