Shells and nucleus from the same sample, fresh water pond, China

 

 

Difflugia distenda (Penard, 1899) Ogden, 1983

Original name: Difflugia acuminata var. inflata Penard, 1899

 

Diagnosis: Shell pyriform with the aboral extremity acutely curved towards a small central tubular horn, although the extent of the angle may be less acute in a few specimens. It has an intermediate smooth surface and thickness, being composed mainly of small to medium pieces of quartz, with occasional diatom frustules added. Aperture circular and usually surrounded by an even arrangement of small particles. Nucleus spherical, with a number of granules dispersed in the nucleus.

 

Dimensions: Penard (1902): 230-250 µm; Ogden: 217-270 µm long, breadth 109-135 µm. My measurements: 170-245 µm long.

 

Ecology: fresh water, sediments.

 

Difflugia distenda, nucleus, China
Difflugia distenda = inflata
D. acuminata var. inflata, from Penard 1902 and 1905 (r.)
Difflugia distenda
Length 176-196 µm, from the Netherlands (Diepveen and Naardermeer); two-spines test are not rare within a population.
Length 192-244 µm, from the Netherlands and China (r.)