Difflugia acutissima
Five shells from the same sample; the fourth shell is in lateral view, with biconcave sides; the fifth shell has two spines; 225-265 µm.

Difflugia acutissima Deflandre, 1931

Diagnosis: Shell elongated ovoid with a short, more or less distinct neck. Fundus tapers into a sharp spine. Shell composed of quartz particles, sometimes mixed with fragments of diatom shells. Pseudostome circular.

Dimensions: Deflandre (1931): Shell length 178-233 µm; my measurements 210-265 µm (n>15).

Habitat: I have found this species in the sediments of a ditch in the nature reserve Naardermeer, the Netherlands. Some shells were compressed and exhibited a biconcave shape, which is characteristic of Difflugia biconcava, also present at the same location.

Remarks: In his description of this species, Deflandre compared its shape to a truncated cigar. It can be distinguished from Difflugia acuminata by its short, distinct neck and sharply tapering spine.

Gauthier-Lièvre and Thomas (1958) described a variety, gigas, collected in Algeria and Chad, Africa, with dimensions ranging from 260–295 µm in height and 100–190 µm in diameter. My measurements fall between those of the type and the variety.

Difflugia acutissima
Difflugia acutissima, after Deflandre, 1931
Difflugia acutissima gigas
D. acutissima var. gigas, drawing by Gauthier-Lièvre and Thomas, 1958
Ferry Siemensma, created February 23, 2019; last modified November 30, 2024
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