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

 

 

Difflugia lobostoma Leidy, 1879

 

Diagnosis: test ovoid or subspherical, circular in cross section. Test 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 Difflugia gramen. The key character is the shape and structure of the nucleus, which is completely different from those of D. 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!

 

Difflugia lobostoma is larger than D. gramen.

 

Difflugia lobostoma
Difflugia lobostoma
Difflugia lobostoma
Difflugia lobostoma
D. lobostoma, 32-43 µm
Difflugia lobostoma
Difflugia lobostoma
Difflugia lobostoma
Aperture: trilobed, fourlobed and irregular
Difflugia lobostoma
Difflugia lobostoma
Difflugia lobostoma
Shell length: 180 µm, 136 µm and 178 µm
Difflugia lobostoma
Original drawing from Penard (1902) in Faune Rhizopodique du Bassin du Léman.
Difflugia lobostoma
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.
Difflugia lobostoma in lateral view, 161 µm
Difflugia lobostoma - 170 µm
Difflugia lobostoma, 180 µm long; trilobed aperture with a rim of very small grains
Difflugia lobostoma, 180 µm long, stacked image
Difflugia lobostoma
Difflugia lobostoma
Difflugia lobostoma, 166 µm, trilobed aperture, Naardermeer, the Netherlands
Difflugia lobostoma, pseudostome, stacked image