Heteronema larseni Lee and Patterson, 2000

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 : 501-502

Heteronema larseni Lee and Patterson , n. sp.

(fi gures 6c, 7f, h, i. Type micrograph: fi gure 7h)

Diagnosis. Heteronema , ovate, 35-45 Mm long, with a posterior point and about 36 well-developed pellicular striations. With or without globular pellicular granules.

Description. Cell ovate, 35-45 Mm long, fl attened, with a posterior point to the cell. Approximately 36 pellicular striations follow a S-helix. The striations of the ventral face are more distinct than the dorsal ones. The striations appear to overlap each other, with raised ridges being separated by fl at regions. Some but not all cells have globular granules located along the grooves. This species is capable of squirming movements, but not vigorously so. The anterior fl agellum is about the length of the cell and bends to the right while the cell is swimming. The posterior fl agellum bends to the left while swimming, is slightly longer than the cell and is stronger than the anterior fl agellum. The posterior fl agellum is swollen near its base. The ingestion organelle has two conspicuous thick rods and extends to two-thirds of the length of the cell. Consumes diatoms, one cell containing diatoms up to 17 Mm long. The reservoir is pear-shaped and in the left half of the cell. The nucleus is about 15 Mm long and located in the left side of the cell near the midline. About 2 Mm size refractile bodies lie around the reservoir, ingestion organelle and nucleus. Cells move by skidding in close contact with the substratum. Four cells observed.

Remarks. This species was fi rst described under the name H. ovale by Larsen (1987) and was redescribed by Larsen and Patterson (1990) and Ekebom et al. (1996). Larsen (1987) noted that the cells observed by him differed in cell length from H. ovale as described originally by Kahl (1928) ( H. ovale sensu Kahl measured 25 Mm, those of Larsen measured 35-42 Mm). The cells described by Ekebom et al. (1996) differ from the cells reported here and those described by Larsen because they are smaller (16-24 Mm), have no posterior point to the cell and may have vigorous squirming movements. We have found cells which are consistent with H. ovale sensu Kahl—see below. We conclude that the organisms described by Larsen (1987), Larsen and Patterson (1990) and here are not H. ovale . Heteronema larseni Lee and Patterson , n. sp. is erected for them. This species has been found in tropical Australia, Danish Wadden Sea and Fiji. Previously reported lengths are 20-42 Mm ( Larsen 1987; Larsen and Patterson, 1990) although it is possible that the small cells observed by Larsen and Patterson (1990) may be H. ovale . This species has strong pellicular striations and may have small bodies alongside the striations. Heteronema ovale also has pellicular bodies (see H. ovale below). We do not regard the refractile inclusions (small bodies) as a good diagnostic character of H. larseni . Heteronema larseni can be distinguished from H. exaratum and H. ovale by its larger size, pointed posterior end, and well-developed ingestion organelle.