Algae World: Sellaphora

Sellaphora bacillum

This series of photographs shows an interphase cell of Sellaphora bacillum in girdle view. The six photographs show successively deeper planes within the cell, from close to one side of the girdle to the other. The first and last photographs focus on the two lateral lobes of the chlorplast. One of these (left) contains the base of the pyrenoid; the other does not. Since the pyrenoid also appears triangular when seen 'in valve view' (i.e. perpendicular to the views shown above), it must be tetrahedral. The invaginations into the pyrenoid matrix are obvious in these photographs, as is the central bridge of cytoplasm containing the nucleus. Each of the polar vacuoles contains a strongly refractile volutin granule.

The complete series of 25 images from which these six were chosen can be viewed as a focusable stack, focusing up from the distant side of the girdle. Around the cell are many bacteria, especially on the side closest to the cover-slip (later frames in the sequence: the cell had been lying attached to the cover-slip for several hours).