world of amoeboid organisms

Menu
Difflugia oblonga, drawing from Ehrenberg, 1838. All tests represent the same specimen.

 

Difflugia oblonga Ehrenberg, 1838

Diagnosis: Shell ovoid-elongate, laterally circular, with a smooth surface, generally transparent in appearance, and 110 µm long.

Dimensions: Ehrenberg: 110 µm long; Leidy: 60-580 µm; Cash: 100-300 µm;  Hoogenraad & De Groot: 110-440, sometimes up to 800 µm (pers. comm.). My measurements? See my remarks!

Ecology: In sediments of freshwater ponds, ditches and bogs; also in moist soil.

Remarks: The original description is short but clear: shell oblong (=ovoid-elongate), rounded fundus, smooth, 110 µm long and brownish.

Unfortunately this fairly general description has led to different interpretations and alternations by several authors. For example, Cash and Hopkinson (1909) modified the character “oblong” in “typically oblong or pear-shaped”, and “rounded fundus” in “the crown arched, sometimes furnished with a mamillary protuberance”. They argued that “although this species is now almost universally called Difflugia pyriformis, Ehrenberg’s name has the priority and must be adopted in accordance with the rule of zoological nomenclature”. If you are looking through the literature most species labeled as D. oblonga are pyriform (pear-shaped) and much larger than the length of 110 µm given by Ehrenberg  (Fig. 1).
An other example of misinterpretation of the original description of D. oblonga can be found with Ogden and Hedley (1980) who noticed that D. longicollis Gassowsky, 1936, is similar to D. oblonga in shape, but can easily identified by its size which is 72 – 116 µm. However, tis is curious, as the size given for D. oblonga in the original description is 110 µm!

Two species correspond to the description of Ehrenberg, D. bryophila and D. lanceolata (Fig. 2). Very likely Ehrenberg has observed a specimen of one of these common species, but we will never now which of these species he has used for his description. However, most species identified as D. oblonga belong to the D. pyriformis group. In this regard, it is highly remarkable that Penard in his standard work (1902) never mentioned the name D. oblonga, though he used it in later years, e.g. D. pyriformis var. bryophila became D. oblonga var. bryophila (Wailes & Penard, 1911).

Difflugia oblonga

 

Fig. 1: These drawings were published by Chardez (1967) and labeled as D. oblonga and varieties. Compare the pyriform shape and the size with Ehrenbergs drawing on the left (arrowed and on scale). All shells drawn by Chardez are part of the D. pyriformis complex.
Difflugia oblonga
Fig. 2: D. bryophila (above mid) and D. lanceolata (above, right corner) are common species. Most likely Ehrenberg had a specimen of D. bryophila under observation when he described D. oblonga. (All tests on scale)

 

 

Difflugia bryophila and lanceolata

 

Shells of D. bryophila and the larger D. lanceolata and D. lacustris, all on scale, ranging from 65 to 195 µm and all from the same location, show how difficult it is to distinguish species morphologically.

 

Recent posts

Spiculophrys

Genus Spiculophrys Zlatogursky, 2016 Diagnosis: Centrohelids lacking silica scales but with numerous thin, pointed organic (without any traces of silica) scales tapering towards acute apices. 18S

Read More »

Acanthocystis drakena

From Zlatogursky, 2016 Acanthocystis drakena Zlatogursky, 2016 Diagnosis: Cells are 21.1-30.5 µm (ca. 26.7) in diameter. Cell is covered with oval plate-scales having a margin

Read More »

Choanocystis symna

From Zlatogursky, 2014 Choanocystis symna Zlatogursky, 2014 Diagnosis: Cell body ca. 6.7 µm in diameter. Axopodia three–five times longer than a cell diameter. Plate-scales dumbbell-shaped

Read More »

Acanthocystis costata

From Zlatogursky, 2014 Acanthocystis costata Zlatogursky, 2014 Diagnosis: Cell body ca 9.5 µm in diameter. Axopodia 2–3 times longer than cell diameter. Length of spine-scales

Read More »

Kinetocyst

Left: ultra-structure of a kinetocyst of Raphidiophrys contractilis); right: two kinetocysts in an axopodium. Kinetocysts In centrohelid heliozoa, extrusomes are called kinetocysts, and are present

Read More »

Yogsothoth carteri

Yogsothoth carteri, after Shishkin and Zlatogursky, 2018 Yogsothoth carteri Shishkin and Zlatogursky, 2018 Diagnosis: Individual cells in a colony have a diameter of 9.7-15.2 µm;

Read More »