Conopeum

A conopeum is a thin flap of silica lying along the apical axis on the external valve face, extending unsupported, partially or completely covering the striae. Its proximal margin is formed by the edge of the raphe slit and its distal margin is free. It may be hyaline or finely porous and it may lie flat or may be slightly to distinctly elevated. A conopeum is present on each side of the raphe. In Greek, conopeum means canopy. The plural is conopea.

Conopea are found in genera such as Fallacia, Mastogloia, Nitzschia, Homoeocladia, and Sellaphora.

Details of the conopea are best viewed with SEM, but may be visible with LM as longitudinal lines near the raphe or as unornamented areas of the valve face.

Conopea have been found to contain symbiotic nitrogen-fixing cyanobacteria.

See also pseudoconopeum.

Citations

Lobban, C.S. and Ashworth, M.P. (2022) Homoeocladia C.Agardh reinstated for bilaterally symmetrical conopeate Nitzschia species (Bacillariaceae, Bacillariophyta) Notulae Algarum 267. 9 pp https://notulaealgarum.org/2022/documents/Notulae Algarum No. 267.pdf
Paddock, T.B.B. and Kemp, K.D. (1990) An illustrated survey of the morphological features of the diatom genus Mastogloia Diatom Research 5: 73-103.
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.

Conopeum Copy — External valve face of *Sellaphora californica* (SEM). The arrow marks a conopeum. This species is an example with hyaline conopea extending a short distance from the raphe slit, and appearing as longitudinal lines in the light microscope.

Fallacia Latelongitudinalis Brightened — Outside of the apex of *Fallacia latelongitudinalis* (SEM). This species is an example with finely porous conopea reaching nearly to the valve margin, almost completely covering the striae, and making the valve face appear unornamented in the light microscope. Fascicles of pores spread across each conopeum. A few areolae of the striae under the conopea are visible in the apical openings of the conopea. Scale bar = 1 µm.