Dinema litorale Skuja, 1939

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 : 496-498

Dinema litorale Skuja, 1939

(fi gures 3e, 5d -g)

Description. Cell length varies from 45 to 95 Mm. Cell spindle-shaped to ovate, with about 30 striations running longitudinally along extended cells or helically in contracted cells. Cortical grooves may be underlain by long thin inclusions. The ingestion apparatus is located slightly to the right of the midline of the cell, with two rods clearly visible and extending at least halfway down the cell. Refractile granules cluster around the ingestion apparatus. The fl agellar pocket is di ffi cult to see. Nucleus spherical and slightly posterior. The anterior fl agellum may be as long as the cell. The posterior fl agellum is about 0.5-1.5 times the cell length and is thick at its base and tapers towards the tip—as in Anisonema . Cells move by smooth gliding interrupted with sudden stops, they may jerk back while becoming more spherical and then continue gliding. Often with many refractile granules. Consume diatoms up to 56 Mm long. Sometimes (late cultures) common. Observations based on 15 cells.

Remarks. Dinema litorale is distinguished from other species of Dinema except D. griseolum Perty, 1852 by its large size and its distinct pellicular striations. According to Skuja (1939), D. litorale is distinguished from D. griseolum by a more spindle-shaped body, the lack of granules (muciferous bodies) under cell surface, fewer fi ne and thick spiral striations and the somewhat larger size of D. griseolum . We found cells without muciferous bodies lining the pellicular strips of cells that could not otherwise be distingushed from those with inclusions (as in D. griseolum ). We note that Dinema griseolum may be a senior synonym of Dinema litorale Skuja, 1939 . The range of lengths was previously reported to be 40-95 Mm ( Skuja, 1939; Larsen, 1987; Larsen and Patterson, 1990; Ekebom et al., 1996). Our observations are broadly in agreement with previous authors, but the two-fold size range suggests that more than one species may be included. We note some minor differences between earlier reports and our observations in respect of the number of grooves and of the relative lengths of the fl agella. Cells without one fl agellum or with truncated fl agella were often observed, so we do not regard fl agellar length as a good diagnostic character. In cells observed by us, the nucleus was not located at the extreme posterior as indicated by Larsen and Patterson (1990), but was similar to the position indicated by Ekebom et al. (1996) and Skuja (1939). Previously reported from marine sites in subtropical and tropical Australia, Brazil, Danish Wadden Sea ( Larsen, 1987; Larsen and Patterson, 1990; Ekebom et al., 1996).

Dinema platysomum ( Skuja, 1939) Lee and Patterson , n. comb. (fi gures 3c, 4j, 5a -c)

Description. Cell outline elliptical, 20-28 Mm long, 9-14 Mm wide, fl attened, fl exible when being compressed. With about 20 pellicular striations on ventral and dorsal faces of the cell. The ventral striations are more distinct than the dorsal ones. The two fl agella are unequal in length. The anterior fl agellum is slightly thickened, is about 1.2 times the length of the cell and sweeps from side to side. The trailing posterior fl agellum is thicker and is most strongly developed proximally. It lies in a ventral groove and is about 2-2.5 times the length of the cell. The fl agellar pocket is located in the left side of the cell and the large elliptical nucleus is located on the right half in the middle of the cell. The ingestion apparatus may be easily seen. Cells occasionally stop and jerk when changing direction and then move again. The cells contained diatoms. Rarely observed. Description based on observations of fi ve cells.

Remarks. This species was described as Anisonema platysomum from freshwater sites by Skuja in 1939. We assign this species to Dinema because it has an ingestion apparatus. This species is indistinguishable from Dinema inaequale Larsen and Patterson, 1990 in size, shape, and in having an ingestion apparatus and a ventral groove, and we regard the species as synonymous. This species has been found in marine sites in tropical Australia and Fiji and the cell length was previously reported to be 26-30 Mm ( Larsen and Patterson, 1990; Ekebom et al., 1996). Our observations are in agreement with observations of Skuja (1939) and Larsen and Patterson (1990). Cells observed by us were in the lower part of the range. Most cells had a nucleus at the right middle of the cell, but one cell had a nucleus in the right posterior part of the cell. We note therefore that the position of the nucleus may not be a reliable diagnostic character. Dinema platysomum is similar in general appearance to Dinema validum Larsen and Patterson, 1990 , which can be distinguished by strong ventral pellicular striations and thin pellicle. This species resembles a few of species of the genus Anisonema , such as A. acinus and A. glaciale but can be distinguished by the ingestion apparatus and fl exible body.