Leptomyxa fragilis (Penard, 1904) Siemensma, 1987

Diagnosis: Large amoeba, polypodial form usually covered with detritus; numerous small nuclei, each with 1-3 irregular shaped nucleoli; cytoplasm clear, sometimes with some small mineral grains and diatom frustules; subpseudopodia often broadly lobed with a deep incision between the lobes; several contractile vacuoles, which can grow large and sometimes melt together; no crystals; hyaloplasm at the anterior end, with eruptive bulges; hyaloplasm may run back along the sides, just as in Rhizamoeba-species.

Dimensions: My measurements 250—480 µm, nuclei 6.2—8.4 µm (Penard 5—7 µm); Penard (1890) gives as average 180—300µm, but his stained mounts in the collection of the Natural History Museum in London contain three specimens with the following dimensions: 398, 403 and 456 µm.

Habitat: Freshwater. I found this species in sediment of a small forest stream near Epe (1980), the Netherlands.

Remarks: It is possible that this species is identical to L. reticulata. Photomicrographs 11 and 13 by Pussard (1976) bear a striking resemblance to the specimens I have observed. However, I have never seen the flat plasmodium. This form is probably only employed on agar. Both Pussard (1976) and Goody (1914) state that the nuclei of L. reticulata usually have one nucleus. Penard saw one, two and three nucleoli.
The number of nuclei is numerous. Penard speaks of several hundred. I could see this on his stained slides in London. In one mount I could count more than two hundred nuclei. I have tried to count the number of nuclei in my specimens. I stained an amoeba with borax carmine and counted over 400 nuclei.
The large vacuoles are striking, the largest with a diameter of 41 µm. These large vacuoles were also visible in the London collection.