Description of Colpoda augustini
provided by BioPedia
Colpodid ciliate, about 30-60 x 20-40 microns. Shape rather variable highly reminiscent of C. maupasi, keel however more acutely tapered, enabling rather reliable distinction between these species even under low magnification. Right margin (dorsal side) convex left (ventral side) distinctly sigmoid through marked indentation at oral apparatus and distinct postoral vaulting; well-nourished specimens almost globular postorally. Slightly flattened broadly wedge-shaped in ventral view no postoral sack. Macronucleus globular, near centre of cell, with single rope-like or reticulate nucleolus. Nuclear membrane in both populations with tufted argyrophilic structures the nature of which is not known. Micronucleus ellipsoid, flattened, attached to macronucleus. Contractile vacuole in posterior end single excretory pore slightly subterminally in median of left side. Cortex indistinctly furrowed by somatic kineties. Mucocysts difficult to recognize in living cells. Cytoplasm with few rod-shaped crystals and many 5-10 microns sized food vacuoles containing bacteria. Movement moderately rapid, often peculiarly tumbling due to tapered preoral and globular postoral portion. Kineties of right side extend almost parallel to straight preoral suture and longitudinal body axis respectively whereas those of left side abut at right angles. Some postoral dikinetids lack anterior cilium. 3-5, usually 4 postoral kineties. Oral apparatus in anterior third. Vestibulum small covers only proximal third of knee-to-boomerang-shaped left polykinetid. This unique shape of the left polykinetid is constant in about 30 populations from around the world; it facilitates ready and reliable identification. The cilia of its distal kineties are slightly elongated forming an indistinct "beard". Right polykinetid composed of 5-8 kineties with rather short (about 3 microns) cilia.
