Description of Pelodinium reniforme

Ciliate, 40-50 x 30-45 microns. Shape ellipsoid to lens-shaped, laterally strongly flattened. Ventral side usually straight and with rib and projections. Dorsal side semicircular, smooth. Posterior end broadly rounded, with 2 roundish recesses, which are surrounded by 6 inconspicuous spines. Macronucleus usually two. Contractile vacuole below the adoral membranelle zone, i.e. ventral in the posterior end. Body rigidly. Pellicula shining and transparent, usually clearly serrated. On the left side three rows (1/2 to 2/3 body length). Rear range of the right side with three ciliary rows (1/3 body length). Cilia long. At the front end a "frontal ciliary band", which begins on the left side and pulls crosswise over the ventral surface up to the median of the right side; to the rear the furrows prominent from this band gather on the usually rounded off spine, which is set in by 2 typical ear-form recesses. Adoral membranelle zone in a pit in the centre of the ventral side, seen only with difficulty in living cells, consists of 12-15 membranes. What seem to be endosymbiotic bacteria occur in the cytoplasm.