Difflugia viscidula
 
D. viscidula 273-307 µm

 

Difflugia viscidula Penard, 1902 pars

Diagnosis: shell elongated oblong, usually with a distinct neck, composed of much smaller particles than the rest of the shell; with zoochlorellae.

Dimensions: Penard (1902): 180-260 µm; my measurements: length 222-460 µm (mean 365 µm); width 118-200 µm; aperture 56-101 µm.

Ecology: fresh water; Switzerland; the Netherlands (Naardermeer and several other locations).

Remarks: Penard described this species in 1902 as D. viscidula, but in 1905 he wrote that he had made a mistake by which he thought that D. lemani was a much smaller species. He noticed erroneously 31-80 µm, instead of 180-310 µm, as given by Blanc (1892). However, he gives three different drawings (see below). No 1 and 2 seem to be the same as described by Blanc, but no 3 is different by having a clear neck. I have found both types and I think that there are at least two different species. The oblong (acorn) type and the elongated one with the neck.

Difflugia viscidula
Drawing: Penard (1902) in Faune Rhizopodique du Bassin du Léman. In 1905 he wrote that this should be D. lemani Blanc 1892, but test no 3 is in my opinion another species.
Difflugia viscidula
Difflugia viscidula, 292 µm – stacked image
Difflugia viscidula
Difflugia viscidula, 326 µm – 428 µm, Naardermeer, one sample; scale bar = 100 µm.
Difflugia viscidula
Difflugia viscidula, nucleus in squeezed cell. Notice the zoochlorellae and the ingested diatoms.
Difflugia viscidula
Difflugia viscidula, shell ratio Length / Width (n=39)

 

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