Notosolenus similis 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 : 512-513

Notosolenus similis Skuja, 1939

(fi gures 9g, 10m, n)

Description. Cell outline oblong, 10-22 Mm long (mostly 12-17 Mm) and 6-12 Mm wide, fl attened. Usually with a narrowed anterior end and a rounded posterior end. The right half of the cell is thicker than the left half. The organism has a dorsal groove in the left-hand side of the cell with a well-developed undulating ridge and may or may not have a shallow median ventral groove. The two fl agella are unequal in length; the anterior fl agellum is about 1.0-1.7 times the cell length and the recurrent posterior fl agellum is about 0.3-0.5 times the cell length. The reservoir lies in the right side of the cell, is usually roundish and the nucleus is in the left side. Cells glide with the anterior fl agellum in contact with the substratum. Common, especially after coverslips have been in place for several days. Description based on observations of 43 cells.

Remarks. This species was fi rst described by Skuja (1939) from freshwater sites and reported by Larsen and Patterson (1990) from tropical Australia and Brazil. Previously reported cell length ranges from 12 to 18 Mm ( Skuja, 1939; Larsen and Patterson, 1990). According to the original description of Skuja (1939), N. similis has a shallow ventral groove. Larsen and Patterson (1990) referred to a ventral groove, but their illustration (fi gure 21c) suggests a dorsal groove and this has been con fi rmed by reference to original notes. Although we have observed a shallow ventral groove in some cells, the major groove is located dorsally.

This species resembles N. lashue in size and in having a dorsal groove with a ridge, but it differs because N. lashue has a ventral groove in addition to the dorsal groove and a fi ne ventral ridge and because N. lashue is ovate or pear-shaped rather than oblong. Notosolenus similis can be easily confused with N. apocamptus Stokes, 1884 (6.5-16 Mm) which is usually smaller than N. similis (12-22 Mm) and has a deep dorsal groove—but this is without an undulating ridge and is located centrally not to the left of the cell. Notosolenus similis also resembles N. stenoschismus Skuja, 1939 in size and in dorsal groove, but N. stenoschismus can be distinguished by having indistinct longitudinal striations. The striations were noted by Skuja (1939) but not fi gured, and their presence has subsequently been con fi rmed (Schroeckh and Patterson, unpubl.). Notosolenus stenoschismus was not reported as having a thickened right margin to the groove. The distinctions between these species deserve further attention. Notosolenus similis is very similar to Petalomonas involuta Skuja, 1939 in cell length and general appearance, but is distinguished by the presence of

a recurrent fl agellum.