Frustula

Frustula refers to the siliceous cell walls of diatoms, a major group of microalgae found in oceans, rivers, and soils. The frustule is composed mainly of hydrated silica and an organic matrix, and it is divided into two overlapping halves called the epitheca and hypotheca. Together these valves form a protective shell with intricate patterns of pores, ribs, and perforations, often including a raphe system in species capable of gliding.

During the life of a diatom, the frustule is formed inside the cell and is shed and rebuilt as cells divide. In a typical asexual division, each daughter cell inherits one valve from the parent and constructs a new complementary valve, which can lead to a gradual decrease in average cell size over successive generations until sexual reproduction restores maximum size. The frustule’s detailed architecture is produced by biological control of silica deposition and is species-specific, making it valuable for identification.

Frustules persist extensively after the organism dies, becoming a major component of diatomaceous deposits. Diatomaceous earth, derived from accumulated frustules, has industrial uses in filtration, polishing, and as a mild abrasive. In paleontology and earth sciences, fossil frustules are critical microfossils used in biostratigraphy, paleoenvironmental reconstruction, and climate studies due to their abundance, preservation potential, and sensitive responses to environmental conditions.

Frustules occur in a wide range of aquatic habitats, from freshwater to marine systems, and their diversity and preserved silica skeletons provide essential insights into modern ecology, ancient environments, and industrial applications.