Heteronema exaratum 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 : 499-501

Heteronema exaratum Larsen and Patterson, 1990

(fi gures 6a, 7a -e)

Description. Cell ovate, 8-18 Mm long, 6-13 Mm wide, dorso-ventrall y fl attened, metabolic, but not vigorously so, with a small ingestion organelle. With pellicular striations following a S-helix on both faces of the cell. The dorsal striations are more strongly developed than the ventral ones. This species usually moves by skidding in a counter-clockwise direction. Two fl agella are similar in length, are slightly longer than the cell and point in different directions when moving; the anterior fl agellum points to the right, the posterior fl agellum to the left. The posterior fl agellum has a knob at its base within the fl agellar pocket and is stronger than the anterior fl agellum. In immotile cells, the fl agella coil up. The reservoir and nucleus are in the left side of the cell. Common.

Remarks. This species has been found in marine sites in subtropical and tropical Australia, and Fiji with previously reported lengths from 15 to 20 Mm ( Larsen and Patterson, 1990; Patterson and Simpson, 1996). We have observed cells 8 Mm long, and although we have not seen an ingestion organelle the cells are otherwise in agreement with previous accounts of H. exaratum . This species can be confused with H. ovale (see remarks to H. ovale ), but is distinguished by less vigorous squirming, the more weakly developed pellicular striations, and the differences between dorsal and ventral striations. It can be distinguished from H. larseni (below) because H. exaratum has weaker pellicular striations, is smaller, does not have a pointed posterior end, and has a less visible ingestion apparatus.

Heteronema globuliferum (Ehrenberg, 1838) Stein, 1878 (fi gures 6b, 7g)

Description. Cell outline elongate ovate, 20 Mm long and about 8-11 Mm wide, fl attened, with squirming movement and with pellicular striations following a S-helix. Two emergent fl agella are similar in width. The anterior fl agellum is approximately 2-2.5 times the length of the cell and is longer than the posterior fl agellum which is slightly longer than the cell. The ingestion organelle may be di ffi cult to see. The reservoir is in the left ventral side of the cell and the nucleus is in the posterior part of the cell. Refractile bodies lie under the cell surface. Cells move by gliding. Rarely observed.

Remarks. Previous reported cell lengths range from 17 to 39 Mm ( Lemmermann, 1913; Stein, 1878; Huber-Pestalozzi, 1955; Larsen and Patterson, 1990). This species was found in marine sites in Brazil and Fiji ( Larsen and Patterson, 1990). Generally, our observations are in agreement with Larsen and Patterson (1990). This species is distinguished by its elongate ovate shape. This species is similar to H. nebulosum Dujardin, 1841 in general appearance, but H. nebulosum is bigger and has a short recurrent fl agellum. Peranema globulosa Dujardin, 1841 and H. sacculus Skuja, 1948 are synonyms of H. globuliferum ( Stein, 1878; Larsen and Patterson, 1990). Heteronema abruptum Skuja, 1939 also appears to be a junior synonym of H. globuliferum . Skuja described H. abruptum without reference to H. globuliferum . Heteronema abruptum measures 17-30 Mm which is within the range of H. globuliferum . The anterior fl agellum of H. abruptum is about twice the cell length and the posterior fl agellum is about 1-1.5 times the cell length. There are minor differences which we do not regard as signi fi cant; they have slightly different shapes and H. abruptum is slightly broader.