Areola

An areola is one of the pores in a row that forms a stria on a valve. The plural is areolae.

The type of the areola can be important in diatom taxonomy. Some examples of different types of areolae include lineolate (Navicula), punctate (Gomphoneis) and loculate (Diploneis).

An areola may be covered partly or completely by one or two thin, porous layers of silica known as an occlusion. Electron microscopy is usually needed to resolve occlusions.

See occlusion for more detail.

Alternative Terms

punctum

A general term for a round or oval pore in the silica wall of a diatom. The plural is puncta.

N Tripunctata Lineolate Areolae
Image Credit: Marina Potapova
An SEM image of the lineolate areolae of Navicula tripunctata. The arrow depicts one areola. These areolae are elongated in the apical direction, which is a characteristic of the genus Navicula. The areolae are arranged in rows to form the striae of the valve.
A Crassipunctata Areolae
Image Credit: Marina Potapova
A light micrograph of the valve mantle of Aulacoseira crassipunctata, showing many round areolae.
A Crassipunctata Areola
Image Credit: Marina Potapova
SEM image of an areola of Aulacoseira crassipunctata, with volae extending from its sides. Scale bar = 0.5 µm.