Petalomonas minuta Hollande, 1942

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 : 521-523

Petalomonas minuta Hollande, 1942

(fi gures 14e, 15m)

Description. Cell outline ovate, 6-10 Mm long (mostly 6-7 Mm), 4-6 Mm wide, fl attened, with a deep longitudinal groove on the dorsal face. One cell had two indistinct ventral ridges which were hard to see, and two cells had a narrow ventral groove-like slit. With one fl agellum inserting into a reservoir in the right-hand side of the cell, fl agellum about same length as the cell. The nucleus is in the left-hand side of the cell. Glides. Often common. Description based on observations of 16 cells.

Remarks. This species was fi rst described as P. mediocanellata var. pusilla by Klebs in 1893. This is not the same as P. pusilla Skuja, 1948 which differs in the absence of a surface groove. Because of the principle of co-ordination of the ICZN (Article 46) P. pusilla Skuja 1948 is a junior homonym. The same organism as observed by Klebs was described by Hollande (1942) as P. minuta . Although the correct name for this species under the provisions of the the ICZN is P. pusilla Klebs 1893 , we believe that such usage would be confusing and given that P. pusilla Skuja 1948 is the legitimate use of this homonym under the regulations of the International Code of Botanical Nomenclature ( Greuter et al., 1994), we adopt the approach of Larsen and Patterson (1990) and refer to this species as P. minuta Hollande, 1942 . Like Larsen and Patterson (1990), we regard P. minutula Christen, 1962 as a junior synonym. Petalomonas mediocanellata var. pusilla Klebs, 1893 and P. minutula Christen, 1962 were described from freshwater sites. The drawing in Klebs shows the surface discontinuity by which this species is distinguished. Previously reported cell length for this species is 6-12 Mm. This species has been found in marine sites in subtropical and tropical Australia, Brazil, Danish Wadden Sea, Denmark, Fiji, Gulf of Finland and North Atlantic ( Larsen, 1987; Larsen and Patterson 1990; Vørs, 1992a, 1992b; Patterson et al., 1993; Patterson and Simpson, 1996). Since the description of Hollande (1942), P. minuta has been described as having a deep ventral groove, but Patterson and Simpson (1996) showed that the groove was dorsal. We con fi rm our cells have a deep dorsal groove. Our observations included one cell with two indistinct ventral ridges which could easily be overlooked and two cells having a narrow ventral groove-like slit. This species is otherwise in agreement with observations of Patterson and Simpson (1996).

This species resembles P. poosilla Larsen and Patterson, 1990 in general cell shape, cell length and fl agellum length, but it can be distinguished by its deep dorsal groove. It resembles P. minor in length, but it does not have a dorsal keel. This species resembles P. ventritracta Skuja, 1939 in general appearance, but P. ventritracta has a ventral groove and is bigger. It is similar to Notosolenus apocamptus Stokes, 1884 in general appearance, cell length and in having a deep longitudinal dorsal groove, but it can be distinguished by the lack of a posterior fl agellum and by its short anterior fl agellum.