Nephrocytium is a genus of green algae in the class Chlorophyceae. Formerly placed in the family Oocystaceae, it is currently placed in its own family, Nephrocytiaceae.[1]
Nephrocytium consists of colonies of 4, 8, or 16 asymmetrical cells surrounded by a spherical to ovoid layer of mucilage, which is formed when the mother cell wall expands and gelatinizes. Individual cells are kidney-shaped to ovoid, containing one chloroplast lining the inside of the cell membrane, each with one pyrenoid.[2]
Reproduction occurs asexually. It exclusively forms autospores, and does not appear to have a flagellated stage in its life cycle.[1]
Similar genera include Nephrochlamys and Juranyiella; Nephrochlamys differs in having cells that lack pyrenoids, while Juranyiella has granules dotted on the cell wall surface.[3]
Species are distinguished mainly by the shape of the cells (particularly at their apices), cell sizes, and length-to-width ratios. However, cells enlarge during their life cycle, which must be taken into account while identifying Nephrocytium species.[1]