Bryometopus sphagni

Colpodid ciliate, length 50-180 microns. Shape variable: reniform, elliptical, or oval with posterior end either narrowed or widened. Right (dorsal) body margin usually more convex than left, which is indented more or less distinctly near distal end of adoral zone of organelles. Starved and normally fed individuals flattened about 2:1, well-fed specimens postorally often inflated. Cells sometimes very fragile, may deform and move amoebae-like under coverslip pressure. Macronucleus ellipsoid (about 2:1), fusiform or reniform; near mid-body between proximal end of adoral zone and left body margin, in some populations surrounded by many 1-2 microns sized roundish globules; many tiny nucleoli. 1-4 (usually at least 2) ellipsoid micronuclei attached to macronucleus. Contractile vacuole surrounded by small collecting vesicles during diastole. Excretory pore with distinct, short canal in postoral (ventral) suture between posterior half and posterior third of cell. Cytopyge in postoral suture near end of cell; sometimes large vacuole with food remnants adjacent. Cortex slightly furrowed by somatic kineties, between each 2 ciliary rows about 5 files of colourless granules which stain blue with methyl green-pyronin and eventually form a voluminous, structureless coat around cell. Cytoplasm colourless, granulated, crammed with small and very large food vacuoles in well-fed specimens. Movement moderately rapid, gliding or rotating about main body axis, may attach to soil particles and detritus. 40-65 moderately spirally coursing kineties with about 8 microns long cilia markedly condensed beneath adoral zone of organelles. Postoral suture distinct, occasionally a second suture on left side due to some shortened postoral kineties. Sometimes a short kinety along paroral membrane. In most parts of the cell, only one basal body of each pair bears a cilium. Ciliated dikinetids occur near the adoral zone of organelles and are scattered over the entire cell. Oral aperture conspicuous, occupies anterior left quadrant of cell, orientated at about 45 degrees to longitudinal body axis. Vestibulum broad-elliptical, deepened spoon-like, right (dorsal) wall distinctly striated by fibres originating from paroral membrane, appears flabby and blister-like; deepens during feeding. Pharynx long, which is however only recognizable during feeding, and containing proximal third of adoral zone of organelles. Paroral membrane curved to C-shaped, in vivo apparently comprising single, fused cilia. Silver preparations and SEM-micrographs, however, show it to be composed of tightly spaced, ciliated dikinetids; middle region in some specimens apparently composed of short, oblique kineties having 3-4 basal bodies each. Adoral zone sigmoid, comprises about 45 organelles with 2 rows of ciliated basal bodies each. A fibre originates at the distal end of each organelle and unites with fibres of adjacent organelles to form stellate aggregations underneath the zone. A thin fibre of each aggregate extends to the proximal end of the organelles and merges with those from the other aggregates to generate a long bundle which extends along the left margin of the adoral zone. This fibre forms a conspicuous, ramified nodule at the proximal end of the adoral zone.