Ancyromonas melba Patterson and Simpson 1996

David J. Patterson
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Containing group: Ancyromonas


Cells are 5-7 µm long, oval shaped and dorso-ventrally flattened with the ventral side hollowed. The anterior end of the cell is set off by a ventral groove running from the left lateral margin to the right ventral part of the cell. The resulting 'snout' has a few indistinct granules running along it. The vental groove continues longitudinally as a slight ventral crease. The cell usually glides on a posterior flagellum which emerges near the anterior-most termination of the ventral groove. This flagellum is usually held under the cell during gliding. The posterior flagellum is 1-2 times cell length and tapers gradually along its length. The anterior flagellum emerges from a slight depression at the right anterior end of the cell and sweeps in front of the cell as it glides. This flagellum is about the length of the cell and is of similar thickness as the posterior flagellum.

This species has been reported from hypersaline habitats in Western Australia and from Antarctica (Patterson and Simpson, 1996).


This species is strongly reminiscent of the widespread and common Ancyromonas sigmoides in size, dorso-ventral flattening, gliding, presence of a groove from left margin to right ventral side of cell, refractile granules along the snout, posterior flagellum arising from ventral depression, and anterior flagellum if present arising from small depression near the base of the snout. It can be distinguished from A. sigmoides because, in A. sigmoides, the anterior flagellum is short or non-existent. Also, the groove in A. melba is located exclusively on the ventral surface, while the posterior part of the groove of A. sigmoides runs along the margin of the cell. In A. melba cells the recurrent flagellum lies closer to the mid-line of the body, whereas in A. sigmoides it is located marginally or projects from the side of the cell, and A. melba is usually larger and appears more ventrally hollowed.

The prominent anterior flagellum of A. melba makes it easy to distinguish this species from Metopion fluens. Caecitellus parvulus has a prominent anterior flagellum like A. melba but differs because the two flagella appear to emerge from the anterio-posterior axis of the cell. Caecitellus has an ingestion apparatus supported by a hoop of cytoskeletal material and no rostrum.


Patterson D. J. and Simpson, A. G. B. 1996. Heterotrophic flagellates from coastal marine and hypersaline sediments in Western Australia. European Journal of Protistology 32:423-448.

Title Illustrations
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Scientific Name Ancyromonas melba
Image Use creative commons This media file is licensed under the Creative Commons Attribution License - Version 3.0.
Copyright © 2000 David J. Patterson
Scientific Name Ancyromonas melba
Comments Light micrographs of living cells (Differential Interference Contrast)
Specimen Condition Live Specimen
Copyright © 2000 David J. Patterson and Alastair Simpson
About This Page

David J. Patterson
Marine Biological Laboratory, Woods Hole, Massachusetts, USA

Page: Tree of Life Ancyromonas melba Patterson and Simpson 1996. Authored by David J. Patterson. The TEXT of this page is licensed under the Creative Commons Attribution License - Version 3.0. Note that images and other media featured on this page are each governed by their own license, and they may or may not be available for reuse. Click on an image or a media link to access the media data window, which provides the relevant licensing information. For the general terms and conditions of ToL material reuse and redistribution, please see the Tree of Life Copyright Policies.

Citing this page:

Patterson, David J. 2000. Ancyromonas melba Patterson and Simpson 1996. Version 04 October 2000. in The Tree of Life Web Project,

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