world of amoeboid organisms

D. mulanensis
D. mulanensis, after Yang et al., 2015

Difflugia mulanensis Yang, Meisterfeld, Zhang and Shen, 2015

Diagnosis: Shell elongate ovoid like a vase, with a distinct long neck, large, circular, flat or funnel-like collar, rim never bent backward. Small angular particles and medium flattish pieces of quartz. . Single ovular nucleus with many nucleoli.

Dimensions: Length 90-128 µm; width 61-81 µm; collar diameter 65-95 µm; aperture 27-47; nuclear diameter 22–25 µm.

Ecology: D. mulanensis was found in plankton of the oligotrophic, slightly acid Lake Mulan, Hubei Province, China.

Description: The shell is yellowish to brown and semitransparent. It looks like a spherical to elliptical vase with a large apertural collar. The test is 1.16–1.61 times longer than the diameter of the collar, symmetrical in longitudinal and apertural view. It consists of a large circular collar and a tall shell belly with a distinct neck. The aperture is circular. The collar is dish-like or low-funnel-shaped, forming an angle of 115°–160°; the apertural funnel has a height of 11–24% of the total length, and its basal (neck) diameter is 0.39–0.74 times the collar diameter; its margin is ragged. The belly (or main body) is circular in cross section, the narrowest cross section (neck) lies just below the collar, gradually expanding (71–171); the maximal width is normally located in the posterior 22–31% of the shell, with its greatest diameter 0.73–1.06 times the collar diameter. The aboral end is always rounded, never with a protuberance, horn or spine. The shell wall is composed of small angular particles and medium flattish pieces of quartz or other forms of silica (xenosomes), including pieces which appear to be parts of the frustules of centric diatoms, fitted together to give a smooth surface and a regular outline. The collar is made of smaller flattish particles. No obvious cement structures are recognizable in the scanning electron microscope.
The cell body possesses long, sometimes branched, finger-like, and fine granular pseudopodia with rounded ends. The number of pseudopodia generally varies from one to half a dozen, and their measurement ranges in length generally from 10 to 120 µm and ranges in width from 3 to 8 µm (usually about 5 µm). Living specimens usually move slowly over a glass slide in an upright position with the aperture facing the slide by a generally steady flow of cytoplasm. In moving specimens the cell body commonly occupies the greater part of the anterior shell cavity around the aperture, leaving the posterior portion of the shell empty. Notably, in some specimens, one or two pseudopodia usually extend from the aperture to the back of the shell. In fully extended condition, the pseudopodia may exceed the aboral end along the shell. Epipodes attached to the internal walls have been seen. A single spherical nucleus is generally located in the posterior part of the cell. It is of ovular type (see Meisterfeld 2002) with many nucleoli. A gas vacuole was often clearly visible in the anterior body part of floating specimens.

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