Dinema validum Larsen and Patterson, 1990

Lee, Won Je & Patterson, David J., 2000, Heterotrophic flagellates (Protista) from marine sediments of Botany Bay, Australia, Journal of Natural History 34, pp. 483-562 : 498

Dinema validum Larsen and Patterson, 1990

(fi gures 3d, 5h, i)

Description. Cell outline oblong to ovate, 32-53 Mm long, 22-27 Mm wide, with slightly thickened pellicle. About 16 wide longitudinal striations occur on both faces of the cell and slightly follow a S-helix. Dorsal striations are more distinct than ventral ones. The anterior fl agellum is as long as the cell and beats with a sweeping motion. The posterior fl agellum is approximately 3 times the cell length, is thicker than the anterior fl agellum and emerges as a hook from the fl agellar pocket which is in the left-hand side of the cell. The ingestion apparatus has two rods but may be di ffi cult to see. It extends halfway down the cell. This species consumed diatoms as long as 16 Mm. The nucleus is usually in the right posterior end of the cell but may be in the left-hand side. Moves by gliding and may undergo squirming movements. When changing direction, cells jerk backwards and then continue to move forward. Three cells observed.

Remarks. This species was previously reported from marine sites in subtropical and tropical Australia, Brazil and Fiji, with reported cell lengths from 26 to 38 Mm ( Larsen and Patterson, 1990; Ekebom et al., 1996; Patterson and Simpson, 1996). Although one of our cells was slightly pointed at both ends and the ingestion apparatus was hard to see, and was very much larger than the previously reported sizes, we assigned the cell to D. validum because of slightly thickened pellicle, hooked posterior fl agellum and squirming movements. One cell observed had its nucleus in the left-hand side of the cell, thus we suspect that the position of a nucleus is not a good diagnostic character. This species is distinguished from other species of the genus Dinema by its wide pellicular striations and the thickness of the recurrent fl agellum; it is distinguished from D. litorale Skuja, 1939 by the smaller number of pellicular striations.