Trinema enchelys
Trinema enchelys

Genus Trinema Dujardin, 1841

Diagnosis: test composed of two types of scales, large circular plates and smaller circular or broad elliptical plates in between or overlapping; aperture subterminal, ventral, circular or broad oval, invaginated, with rows of toothed apertural plates; apertural rim with oval small scales. Nucleus vesicular. Filopodia.

Ecology: very common in water, between mosses and in soil.

Remarks: species are very variable in size and shape and hard to identify.

 

Key to the species:

 

1Aperture circular with a thin border; length of test less than twice the breadth  2
Aperture oval with a thick border; length of shell at least twice the breadth4
2Test small elliptical, length usually < 40 umT. lineare
Test broader, elliptical to ovoid; length usually > 45 µm3
3Test < 80 µmT. enchelys
Test > 100 µmT. grandis
4Anterior end very compressed with a thick anterior lip; aperture slightly invaginatedT. complanatum
Test in side view ovoid; aperture distinctly invaginated, with broad bend anterior lipT. penardi
Trinema penardi
Trinema complanatum
Trinema lineare
Trinema lineare
From Lueftenegger et al 1988
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