Dictyonema hernandezii

The thallus of Dictyonema hernandezii starts as a small, circular crust, and eventually covers large areas of its substrate. It appears gelatinous when wet and has a smooth, shiny surface when dry. The thallus is 300–500 μm thick and comprises a dominant medullary layer with numerous interwoven hyphae. The cyanobacterial filaments are blue-green to yellow-green, with cells measuring 10–12 μm wide and 3–5 μm high.^[2]

One of the main distinguishing features of this species is its peculiar thallus morphology and anatomy. It is strongly compacted and has a unique heteromerous structure, which is otherwise only known from Dictyonema glabratum and its relatives. However, Dictyonema hernandezii is phylogenetically more closely related to species in the Dictyonema sericeum group.^[2] The Ecuadorian D. metallicum, described as a new species in 2013, is morphologically similar to D. hernandezii. It is distinguished by its thin, completely appressed thallus, and its dark blue colour that, when dry, takes on a metallic shimmer.^[3]

Dictyonema hernandezii has been found in two collections in the montane rainforests of southern Costa Rica. It shares its habitat with Dictyonema glabratum and Dictyonema sericeum, and can be found growing on branches within disturbed rainforest patches. The species has been recorded at an elevation of around 1,200 m (3,900 ft) in the Las Cruces Biological Station and Wilson Botanical Garden within the Pacific La Amistad Conservation Area.^[2] It has also been recorded from Valle del Cauca in western Colombia.^[4]