Metopion grandis, 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 : 553-554

Metromonas grandis Larsen and Patterson, 1990

(fi gures 24k -m, 26c -f)

Description. Cell outline leaf-shaped or slightly roundish, 5-10 Mm long (mostly 7-10 Mm), 4-10 Mm wide and about 2 Mm deep, dorso-ventrall y fl attened. One side of the cell appears folded. With two fl agella; a long fl agellum is 1.2-2.2 times the length of the cell and trails behind the cell when gliding. There is a short inactive fl agellum, less than 2 Mm long, which inserts to the right of the major fl agellum and is always present. Cells attach to the substratum with the longer fl agellum and move with a nodding action—like a pendulum. The nucleus is near the fl agellar insertion. Relatively common.

Remarks. This species was described from marine sites in tropical Australia, Brazil, Fiji, Hawaii and cell length reported was 9-12 Mm ( Larsen and Patterson, 1990; Tong et al., 1998). Generally, our observations are in agreement with the observations of Larsen and Patterson (1990), but we observed three different shapes in the cells (fi gures 26c, d, f). Metromonas grandis is relatively common when diatoms are abundant, but is usually less common than M. simplex ( Griessmann, 1913) Larsen and Patterson, 1990 . It is distinguished from M. simplex by its slightly larger size and folded margin. The folded margin may be a good diagnostic character for this species, but in some cells which contain many granules or prey, the folded margin may be di ffi cult to see. This species usually co-occurs with M. simplex . We believe that Tong et al. (1997) included M. grandis within their account of M. simplex (see fi gure 7a in Tong et al., 1997) and that the fi gure 9m referred to as M. simplex in Tong et al. (1998) was of M. grandis , but having consulted original records we con fi rmed that both species were present.

Metromonas simplex ( Griessmann, 1913) Larsen and Patterson, 1990 (fi gures 24n, 26g)

Description. Cell obovate, 3-8 Mm long (mostly 4-7 Mm), 2-6 Mm wide, dorsoventrally fl attened, pellicle smooth. The abflagellar margin of the cell is thicker than the (posterior) margin. Two fl agella of very unequal length arise from the posterior part of the cell. The major fl agellum is always present, is about 1.5-3.0 times the length of the cell and may be attached to the substratum. The short inactive fl agellum is about 1 Mm long and inserts to the right of the major fl agellum. It may be di ffi cult to see. Cells normally attach to the substratum and swing from side to side like a pendulum and the cells may also glide with the cell body in front of the fl agellum. Common. Description based on observations of 85 cells.

Remarks. This species was fi rst described under the name Phyllomitus simplex by Griessmann (1913). It was found in marine sites in Antarctica, Australia, Brazil, Arctic Canada, Denmark, England, Fiji, Gulf of Finland, France, Germany, Arctic Greenland, Hawaii and cell lengths from 4 to 9 Mm were reported ( Griessmann, 1913; Larsen and Patterson, 1990; Vørs, 1992a, 1992b, 1993a; Ekebom et al., 1996; Patterson and Simpson, 1996; Tong, 1997b; Tong et al., 1997, 1998). This species sometimes appears in large numbers. Metromonas simplex feeds on bacteria and fl agellates through the lateral margin of the cell (Patterson unpubl. obs.) or the anterior part of the cell ( Griessmann, 1913).