Description of Colpodella perforans:
Cells are 4-6 x 2-4.5 microns rather elongated, narrowed anteriorly and rounded at the posterior end. The ventral side of the cell is rather concave. Two flagella insert sub-apically. The anterior flagellum is about 0.5 times the cell length and the posterior flagellum is slightly longer (about 2.5 times cell length) and acronematic. Swimming is rapid and rather similar to the swimming in some species of Bodo, with the anterior flagellum coiling around the top of the cell, the posterior flagellum trailing, and rotation about the longitudinal axis. Cells were commonly seen to attach to Paraphysomonas cells, but did not appear to feed. Feeding was observed on a larger cell of unknown identity. Individuals (up to three at one time) attached at their apex to the prey item, with their flagella coiled around the cell.