(®gures 19m, n, 20k)
Description. Cell about 5 Mm long. The insertion sites of the two ¯agella are separated by a protrusion at the anterior of the cell. The anterior ¯agellum has a sine-wave beating pattern and is about 3.5 times the length of the cell, and the posterior ¯agellum is about twice the length of the cell and may attach to the substratum by its tip. The cell moves by swimming with the anterior ¯agellum directed forwards. One cell observed.
Remarks. Pseudobodo tremulans was reported to be 2±8 Mm long and has been found in marine sites in subtropical and tropical Australia, Antarctica, Brazil, Denmark, Hawaii (Griessmann, 1913; Ruinen, 1938; Fenchel, 1982; Larsen and Patterson, 1990; Patterson et al., 1993; Vùrs, 1993b; Fenchel et al., 1995; Patterson and Simpson, 1996; Tong, 1997a, 1997c; Tong et al., 1997). This species may be confused with Cafeteria minuta (Ruinen, 1938) Larsen and Patterson, 1990 but can be distinguished by a collar around the anterior part of the cell in unstressed feeding cells. In our cell we could not observe the anterior collar, but we assigned the cell to Pseudobodo tremulans because of the shape and size of the cell, swimming and feeding behaviour, and lengths of the ¯agella. This species is similar to Pendulomonas adriperis Tong, 1997 in cell length, but is distinguished by the insertion and orientation of the ¯agella, and the beat pattern of the anterior ¯agellum which is sinusoidal and slow in Pendulomonas.