vs

Cocconeis placentula compared with Cocconeis scutellum

Taxonomic Classification

Rank
Kingdom same	Chromista (Chromista)	Chromista (Chromista)
Phylum same	Ochrophyta (Ochrophyta)	Ochrophyta (Ochrophyta)
Class same	Bacillariophyceae (Bacillariophyceae)	Bacillariophyceae (Bacillariophyceae)
Order same	Achnanthales (Achnanthales)	Achnanthales (Achnanthales)
Family same	Cocconeidaceae	Cocconeidaceae
Genus same	Cocconeis	Cocconeis
Species	Cocconeis placentula	Cocconeis scutellum

Evolutionary Relationship

and share a common ancestor at the Genus level: Cocconeis.

View Genus: Cocconeis

Conservation Status

NE — Not Evaluated

Physical Characteristics

Attribute
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Habitat

Native to Asia and Europe and South America, inhabiting ecosystems characteristic of the region.

Range

Distributed across Brazil, Norway, Portugal, Sweden, and Taiwan.

Habitat

Native to Asia and Europe and South America, inhabiting ecosystems characteristic of the region.

Range

Distributed across Brazil, Norway, Portugal, Sweden, and Taiwan.

Cocconeis placentula is among the most ubiquitous and widely studied freshwater and brackish-water diatoms worldwide, serving as a model organism for periphyton ecology and a key species in biological assessment of water quality. A member of the family Cocconeidaceae, this adnate epiphyte produces a characteristic ovoid frustule with fine transapical striae, a well-developed raphe system on one valve, and an elaborate pattern of areolae visible under electron microscopy. The species complex encompasses several morphological varieties (var. placentula, var. lineata, var. euglypta, var. acuta) that differ in fine structural details of the valve ornamentation. Cocconeis placentula colonizes the surfaces of aquatic plants, algae, rocks, and sediment particles in rivers, lakes, and ponds across a vast global range spanning Europe, the Americas, Asia, Africa, and beyond, tolerating a wide range of water temperatures, pH values, and moderate nutrient enrichment. Its abundance varies dramatically with substrate type, light availability, and water chemistry, making community composition data involving this species valuable in diatom-based paleolimnological reconstructions and modern bioassessment indices. As a benthic primary producer, C. placentula contributes substantially to the productivity of the photic benthos and serves as a dietary component for invertebrate grazers. Its remarkable cosmopolitan distribution and ecological flexibility make it one of the defining species of freshwater periphyton communities globally. Conservation status is not formally assessed.

Cocconeis scutellum is a marine and brackish-water diatom in the family Cocconeidaceae, one of the most commonly encountered epiphytic diatoms in coastal ecosystems worldwide. The frustule is broadly oval and relatively large for the genus, with robust silica walls bearing coarse transapical striae that give the valve a distinctive, shield-like appearance—a morphology reflected in the species epithet 'scutellum,' Latin for small shield. This species is a strict epiphyte in marine environments, attaching to the surfaces of seagrasses, macroalgae such as Ulva and Zostera, coralline algae, and other benthic substrates in shallow intertidal and subtidal zones. Cocconeis scutellum has been documented from coastal habitats across the Atlantic, Pacific, and Indian Oceans, with records from temperate and tropical regions including South America, Europe, and the Indo-Pacific, reflecting its cosmopolitan marine distribution. The species is a basal component of coastal food webs: dense epiphytic biofilms including C. scutellum are grazed by amphipods, gastropods, sea urchins, and small fish, transferring photosynthetically fixed carbon up the food chain. In estuarine environments where freshwater and saltwater mix, C. scutellum may co-occur with freshwater and brackish Cocconeis species, and salinity tolerance experiments indicate the species survives across a broad range of salinities. Its silicon frustules contribute to coastal sediment biosilica content upon cell death. Conservation status is not formally evaluated.