Chaetoceros guide
  1. Cells lightly silicified
  2. Frustules with fused or interlocking setae
  3. Cells joined into colonies
  4. Resting cells heavily silicified

Chaetoceros is a lightly silicified, centric diatom. Valves are elliptical to circular, with a single hollow spine (seta) projecting from each apex, such that each cell possesses four setae. Setae exhibit ultrastructural characters (e.g., spines, poroids) that are taxonomically informative. Radial costae originating from the valve center or central annulus and can be observed using scanning electron microscopy. The cingulum is composed of scale-like copulae. Setae join cells together into filaments, although a few species are solitary. In the microscope, frustules are usually observed in girdle view.

Chaetoceros is a large genus, with over 200 species. It is primarily a marine genus, with only a few representatives in inland waters. In non-marine waters, cells reach their greatest abundances in saline or brine contaminated rivers and lakes.

Living cells are easily destroyed by harsh cleaning methods and so are best observed live or in burn mounts. Furthermore, the architecture of intact filaments and plastid morphology (e.g., number, location) are useful taxonomic characters. Living cells are lightly silicified. Some Chaetoceros species, particularly near-shore marine and non-marine species, produce heavily silicified resting cells which may be preserved in sediments.

Chaetoceros is capable of high growth rates and the cells contain high concentrations of lipids. As a result, Chaetoceros is a potential source for the harvesting of lipids for biofuels.