Solarion

Solarion is a rare genus of eukaryote microbes that inhabits shallow marine low-oxygen sediments. The genus contains a single species, Solarion arienae, which is the only member of the family Solarionidae. Alongside Meteora, they form the phylum Caelestes. Solarion was described in 2025 based on a specimen collected in Croatia, but it may be globally distributed. It is characterized by two distinct life-cycle phases: a globular, sun-like cell with protruding stalks—from which the genus gets its name—and an ellipsoid cell with a single long flagellum and tail. Solarion retains a mitochondrially encoded secA protein, a 'primitive' feature seen in very few other eukaryotes.