Microworld

world of amoeboid organisms

Menu
Menu
Difflugia oblonga
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.

Dimensions: Ehrenberg: 110-140 µm long (see remarks); 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 and brownish. Ehrenberg (1938) gives a length of 1/18 “Linie” (=line) for D. oblonga. In the same publication, page 8, he writes that 1/300 mm = 1/676 Linie. A simple calculation then results in a length of 140 µm for his D. oblonga. However, in the French description, below the Latin one, he gives a length of 1/9 mm (= 111 µm). That’s confusing.

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 111-140 µm given by Ehrenberg  (Fig. 1).

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 know 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 and Penard, 1911).
Another 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, this is curious, as the size given for D. oblonga in the original description is 111 µm, up to 140 µm.

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 Ehrenberg’s 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

Bullinularia maxima

Bullinularia maxima – from Bobrov and Mazei, 2020 Bullinularia maxima Bobrov et Mazei, 2020 Diagnosis: Shell brown, opaque, elliptical in ventral view; ventral surface is

Read More »

Bullinularia macroporum

Bullinularia macroporum – from Bobrov and Mazei, 2020 Bullinularia macroporum Bobrov et Mazei, 2020 Diagnosis: Shell yellow-brownish, transparent, circular in ventral view; ventral surface is

Read More »

Nebela golemanskyi

N. golemanskyi, after Todorov, 2010 Nebela golemanskyi Todorov, 2010 Diagnosis: Shell large, colourless and pyriform, with a distinct short neck about one fourth of the

Read More »

Nebela nebeloides

N. nebeloides, after Gauthier-Lièvre and Thomas, 1958 Nebela nebeloides (Gauthier-Lièvre and Thomas, 1958) Todorov et al., 2010 Basionym: Difflugia nebeloides Gauthier-Lièvre and Thomas, 1958 Diagnosis:

Read More »

Difflugia biwae

D. biwae, after Yang and Shen, 2005 Difflugia biwae Kawamura, 1918 Diagnosis: Shell in lateral view fusiform in outline with a straight neck, a conspicuous

Read More »