Anisonema acinus Dujardin, 1841

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 : 495

Anisonema acinus Dujardin, 1841 (fi gures 3a, 4f, g)

Description. Cell outline like a grain of barley, 21-37 Mm long, 13-17 Mm wide, fl attened, with a ventral groove which diminishes posteriorly. With about nine longitudinal pellicular grooves on each of the ventral and dorsal faces of the cell. In some cells, the grooves are fi ne and di ffi cult to see but in a few cells they are deeper. The anterior fl agellum is about 1.5 times the cell length and beats freely from side to side. The trailing posterior fl agellum is about 1.7-3.2 times the length of the cell, is thicker than the anterior fl agellum, lies in the ventral groove, and tapers posteriorly. This species contained diatoms up to 25 Mm long and one cell had four diatoms as long as 17 Mm. The fl agellar pocket is located in the left side of the cell and the nucleus is in the right side. This species glides smoothly, but jerks backwards when changing direction. Commonly observed. Description based on observations of 29 cells.

Remarks. Anisonema acinus was found in marine sites in the Danish Wadden Sea and in tropical Australia and Fiji by Larsen (1987) and Larsen and Patterson (1990), respectively. The length was previously reported to be from 22 to 40 Mm ( Klebs, 1893; Lemmermann, 1913; Huber-Pestalozzi, 1955; Larsen, 1987; Larsen and Patterson, 1990). Generally, our cells are in accordance with the cells described by previous authors. This species is very similar in general appearance and cell length to Anisonema glaciale Larsen and Patterson, 1990 but can be distinguished by the location of the nucleus and the pattern of movement. This species resembles Dinema validum Larsen and Patterson, 1990 in cell length and shape, but it is distinguished because D. validum has an ingestion apparatus, a squirming movement and somewhat thickened pellicle.

Anisonema acinus may have a smooth pellicle or have fi ne pellicular striations ( Klebs, 1893; Lemmermann, 1913; Huber-Pestalozzi, 1955). Skuja (1939) created A. prosgeobium , which resembles A. acinus , but was distinguished by the lack of pellicular striations and because the nucleus lies in the right of the cell. However, all cells described in this study had a nucleus at the same position as in A. prosgeobium . The position of the nucleus may not be a good diagnostic character because it can be changed by food vacuoles ( Larsen, 1987). We observed some cells with smooth pellicle but were otherwise indistinguishable from the individuals identi fi able as A. acinus . We are of the view that A. prosgeobium is a junior synonym of A. acinus . This species is similar to Dinema platysomum ( Skuja, 1939) Lee and Patterson , n. comb. in general appearance, but is not fl exible.