Loculus

A loculus is a chambered areola with the outer surface covered by a type of velum (often a hymen or cribrum) and the inner surface opening through a foramen or other type of unoccluded pore. From Latin for small space. Plural is loculi.

In some species, loculi may be difficult to distinguish from alveoli. A loculus and an alveolus are both chambered openings in the valve wall but typically only the alveolus is transversely elongated.

Also called a loculate areola. A loculate valve has loculi.

Example genera with loculi include Coscinodiscus, Diploneis, Muelleria, Neidium, many Mastogloia, and some rapheless valves of Cocconeis.

See also areola, pseudoloculus, and false pseudoloculus.

Citations

Ross, R., Cox, E.J., Karayeva, N.I., Mann, D.G., Paddock, T.B.B., Simonsen, R. and Sims, P.A. (1979) An amended terminology for the siliceous components of the diatom cell Nova Hedwigia, Beihefte 64: 513-533
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.
Sims, P.A., Williams, D.M. and Ashworth, M. (2018) Examination of type specimens for the genera Odontella and Zygoceros (Bacillariophyceae) with evidence for the new family Odontellaceae and a description of three new genera. Phytotaxa 382: 1-56

Publication Link: 10.11646/phytotaxa.382.1.1

Cerataulus turgidus 030 — External view of fractured valve of *Cerataulus turgidus* (SEM). Loculi are shown with the outer layer of cribra at top of image and inner foramina at bottom . Scale bar = 2 µm.

Coscinodiscus 004 — Internal view of fractured valve of *Coscinodiscus* sp. (SEM). Loculi are shown with outer layer of cribra at top of image and inner foramina at bottom. Scale bar = 2 µm.