Diatonisia

Diatonisia is a genus of microalgae in the diatoms (Bacillariophyta), described as part of freshwater diatoms. The name derives from Greek roots suggesting a distinctive, island-like valve morphology. The genus was first proposed by researchers in 2010 after molecular analyses indicated a clade distinct from related genera such as Diatoma and Navicula. The type species is Diatonisia elongata.

Morphology and characteristics: Diatonisia species have elongate, narrowly fusiform valves with a perforated raphe running along the length. The central area is relatively narrow; the pattern of riblets, or striae, can be uniseriate or biseriate depending on the species. Frustules are composed of silica, and chloroplasts are typically golden-brown, giving the cells their characteristic appearance under light microscopy.

Distribution and habitat: Species have been reported from temperate freshwater lakes and slow-flowing rivers in Europe and North America, with occasional records in brackish estuaries. They tend to inhabit siliceous substrates in clear or moderately clear waters and can be more common in nutrient-balanced systems.

Ecology and life history: Diatonisia species are photoautotrophic and contribute to primary production in freshwater ecosystems. In regional diatom surveys, they often co-occur with other naviculoid diatoms and can form observable assemblages during favorable conditions. Reproduction is primarily asexual through mitotic division; sexual reproduction with auxospore formation is inferred from occasional cytological observations in culture.

Species and taxonomy: Notable described taxa include Diatonisia elongata and Diatonisia indica, with additional species described in regional floras. The taxonomic status of Diatonisia varies among classifications, reflecting broader revisions in diatom phylogeny.