Amastigomonas mutabilis Molina and Nerad 1991

Amastigomonas mutabilis (Griessmann 1913) Molina and Nerad 1991 (Fig. 2u)

Observation: Cells are elliptical, 11 to 16 µm long, dorso-ventrally flattened and flexible. There is a flexible sleeve around the base of the anterior flagellum. The anterior flagellum is about 0.5 times the cell length and the same thickness as the posterior one. The recurrent posterior flagellum is slightly longer than the cell and trails under the body, to which it attaches loosely in a slight groove. The nucleus is situated subapically near the right margin of the cell. Some cells have granules along side the recurrent flagellum. Relatively rare than Amastigomonas debruynei.

Remarks: This species has synonyms: Rhynchomonas mutabilis and Thecamonas mutabilis. It has been reported from marine sites in Agean Sea (Turkey), Australia, Brazil, Denmark, England, France, Greenland, Korea and North Atlantic with lengths of 7–16 µm (Griessmann 1913; Ruinen 1938; Larsen and Patterson 1990; Vørs 1992b, 1993a; Patterson et al. 1993; Patterson and Simpson 1996; Tong 1997b; Tong et al. 1998; Lee and Patterson 2000; Al-Qassab et al. 2002; Lee 2002b, 2006b; Lee et al. 2003; Aydin and Lee 2012). It seems to be cosmopolitan. This species was characterised by the line of granules along side the posterior flagellum (Larsen and Patterson 1990), but some cells lack the granules. Amastigomonas bermudensis Molina and Nerad 1991 is very similar to A. mutabilis in general appearance and their cell length. Further work is required to clarify the identities of these two species.