Cingulum

Central nodule

Clavate

Cingulum is a term that refers to all of the collective elements of the diatom girdle. The cingulum is made up of delicate silica bands (= girdle bands, copulae) that join the two valves of a frustule. Most diatoms possess a cingulum, although some may not. The silica structures of the cingulum may be secreted after vegetative cell division that produces the diatom valve; that is, while the deposition of the silica valves are tied to cell division, the deposition of the cingulum may not be tied to division.

Alternative Term

girdle band

All of the girdle bands make up the cingulum.

copula

All of the copulae make up the cingulum. The first copula (the one positioned next to the valve) is termed the valvocopula.

Citations

Round, F.E., Crawford, R.M. and Mann, D.G. (1990). The Diatoms. Biology and Morphology of the Genera. Cambridge University Press, Cambridge, 747 pp.

Image Credit: Eduardo Morales

The cingulum of Staurosira construens is composed of the series of silica bands between the two valves of the frustule. The arrows indicate the the first girdle band, the valvocopula, of each valve.