Netzelia lobostoma – Microworld

Netzelia lobostoma, 136 µm (left) and 180 µm long

Netzelia lobostoma (Leidy, 1874) Gonzales-Miguens et al, 2021
Difflugia proteiformis Lamarck, 1816
Cucurbitella tricuspis Carter, 1856, Medioli et al., 1987.
Difflugia tricuspis Carter, 1856
Difflugia lobostoma Leidy, 1874

Diagnosis: Shell ovoid or subspherical, circular in cross section. Shell composed of small and medium pieces of quartz, bounded together by organic cement. Aperture with variations of the opening, trilobed or fourlobed or irregular with indistinct lobes, bordered by an irregular raised ridge of small particles. Lobes range from squarish to curved. Aperture often with an indication of a collar. Nucleus with a number of small nucleoli. Zoochlorellae may be present.

Dimensions: My measurements 136-192 µm, nucleus 37-49 µm ; Ogden (1980) 123-186 µm; Penard (1902) 140-170 µm.

Remarks: Based on the shape and structure of the test this species is hard to separate from Netzelia gramen. The key character is the shape and structure of the nucleus, which is completely different from those of N. gramen. In practice however this character is not very useful, as you have to press the cover slip to break the test. If your are lucky, you can see the nucleus – if it comes out of the broken test!

Netzelia lobostoma is larger than N. gramen.

D. lobostoma, 32-43 µm

Aperture: trilobed, fourlobed and irregular

Shell length: 180 µm, 136 µm and 178 µm

From Penard (1902) in Faune Rhizopodique du Bassin du Léman.

When you want to see the nucleus, you can press the cover slip to break the test. If you are lucky, the nucleus comes out of the test. Several times I could observe that also rotifers and rotifer-eggs came out the test. It seems that these rotifer is a parasite on Difflugia-species. I have also seen this phenomenon with D. capreolata.