Scenedesmus quadricauda. Coloured scanning electron micrograph (SEM) of Scenedesmus quadricauda, a flat colony of 4 alga cells. Scenedesmus, a green alga from the Chlorophyceae group, is a small, non-motile, colonial green alga consisting of cells aligned in a flat plate. The colonies most often have two or four cells, but may have 8, 16, or 32 cells.The cells each have two long spines protruding from their outer corners (as seen here). Other cells may have additional spines or chitinous bristles. Each cell contains a single parietal, plate-like chloroplast with a pyrenoid (the site of CO2 fixation). The cell walls may be covered in bumps or reticulations. Scenedesmus is a photosynthetic planktonic organism that is important in the aquatic food chain. Magnification: x 3000 when printed at 10cm wide. Specimen collected from Vietnam courtesy of Mike Allen, Plymouth Marine Laboratory. |