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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ancyromonas

Ancyromonas Kent, 1880 (ref. ID; 4656) or 1880-81 (ref. ID; 6733)

[ref. ID; 5694]
Circumscription; Heterotrophic gliding flagellates, small (<10 um), with one recurrent flagellum and one anterior flagellum. Mostly documented at light microscopical level some ultrastructural information (Mylnikov 1990) under the generic name Heteromita. (ref. ID; 5694)
Ultrastructural identity; Mitochondria with flat cristate. Cell surface supported by materials both within and external to the cell membrane. Two flagella, bases at right angles, three microtubular roots. Ball and cone style extrusomes present. (ref. ID; 5694)
Synapomorphy; None specified. (ref. ID; 5694)
Composition; Single genus with probably only three species. (ref. ID; 5694)
References; Mylnikov 1990: Patterson and Simpson 1996. (ref. ID; 5694)
  1. Ancyromonas sigmoides Kent, 1880 (ref. ID; 4656, 4872 incertae sedis, 4907 incertae sedis)

Ancyromonas sigmoides Kent, 1880 (ref. ID; 4656, 4872 incertae sedis, 4907 incertae sedis)

Descriptions

Gliding flagellate, one trailing acronematic flagellum, with or without a thin anterior flagellum emerging from an anterior depression. Ventral margin of the cell with groove. (ref. ID; 4872)
Cell rounded, anteriorly depressed, laterally compressed. Two heterodynamic flagella. Trailing flagellum conspicuous, about two times as long as cell, with acronematic tip, arises from a groove located one fourth of cell length from anterior end. Anterior flagellum, about two thirds of cell length, very thin and difficult to observe. Contractile vacuole dorsal in anterior end. Movement is a wobbling along the substrate. (ref. ID; 4907)

Comments

Besides the acronematic posterior flagellum, A. sigmoides can be distinguished from the otherwise similar Metopion fluens by the presence of a thin forwardly directed filamentous anterior flagellum instead of a thicker, backwardly directed anterior flagellum in M. fluens. The anterior flagellum may however easily be overlooked in A. sigmoides and the second flagellum may even be absent in both species (Patterson et al. 1993). (ref. ID; 4872)
Ancyromonas sigmoides is a very distinctive flagellate, the combination of groove, conspicuous trailing flagellum and the tiny anterior flagellum being diagnostic. Much confusion has existed about this species. The concept of the species used here is that of Hanel (1979), which is probably not the original concept of Kent (1880). Hanel, however, overlooked the anterior flagellum. Mylnikov (1990) mistook A. sigmoides for a species of Heteromita; Larsen & Patterson (1990) reported it under the name Bodo cephaloporus. (ref. ID; 4907)

Measurements

Length about 4-5 um. Previously reported length ranges 2.5-6 um (Hanel 1979), 3-7.5 (Larsen & Patterson 1990) and 2-7.6 um (Vors 1992). (ref. ID; 4872)
Length 4-4.5 um, length:breadth ratio about 1.5. (ref. ID; 4907)