Plankton critter

Ventral view of a cell of Peridiniella danica. Cells measure approximately 10-20 µm. Within the equatorial groove (Cingulum) lies an undulating flagellum, which is not visible on this image. Another flagellum lies within the Sulcus in the lower half of the cell. In direct proximity to the Sulcus, a greenish vacuole containing the last prey is shining through the cell wall. The apex is on the very top of the upper cell half.

A sip of plankton photographed with visible light (left) and UV-light (right). On the left, a P. danica with filled food vacuole and a few unicellular coccolithophorids with their calcareous scale armour. The unique dinoflagellate nucleus displays oval-shaped chromosomes, which are (almost) always visible whereas all other organisms have such condensed chromosomes only during certain stages of cell fission. Chloroplasts of coccolithophorids light up in vivid red in UV-light (right), which reveals the last bite of the dinoflagellate.

Dinoflagellates proliferate by fission, but the plane of fission is unusually oblique to the cell’s axes of symmetry. That means these cells don’t divide along on of the grooves. In this image, cell nuclei are already separated whereas the cells just started dividing.

A P. danica cell ingested several cells of planktonic Rhodomonas sp., which appear as orange blobs. Every meal is digested in a separate stomach.

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