Conopeum

A thin flap of silica on the external valve face, lying along the apical axis. Hyaline or finely porous. Proximal margin formed by the edge of the raphe slit. Extends unsupported over the valve face. Distal margin is free. May lie flat or may be slightly to distinctly elevated. May partially or completely cover the striae. Found in genera such as Fallacia, Lyrella, Mastogloia, Microcostatus, Nitzschia and Sellaphora. Plural form is conopea. From Greek for canopy.

Details of the conopea are best viewed with the scanning electron microscope, but may be visible with the light microscope 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.

Conopeum Copy
Image Credit: Marina Potapova
An SEM image of the external valve face of Sellaphora californica. 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
Image Credit: Marina Potapova
An SEM image of the outside of the apex of Fallacia latelongitudinalis. 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.

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.