Nuclearia thermophila Yoshida, Nakayam and Inouy, 2008
Diagnosis: Cells having two forms: spherical to subspherical; floating forms non-motile, with radial filopodia, and flattened amoeboid forms, often elongated. Filopodia sometimes branching or knobbed. Nucleus central, with spherical nucleolus. Many food vacuoles and lipid droplet-like vacuoles with homogeneous contents. Golgi body perinuclear and mitochondria with flat cristae. No cell wall or extracellular matrix. Cysts spherical, surrounded by a thick layer of mucus.
Dimensions: Floating spherical forms about 20-40 µm; flattened amoeboid forms measuring 30-65 µm in diameter, reaching to 150 µm when elongated. My measurements: spherical form 10-35 µm (mean 25-30 µm), flattened forms c. 46-60 µm, nucleus c. 10.2 µm, cysts 15-22 µm, with mucous layer up to 47 µ.
Ecology: Freshwater. This species has been described from a warm water lake, hence the name. I found this Nuclearia-species in peat bogs. It multiplied easily in “pond” cultures with a maize grain; feeding on green algae has been observed.
Remarks: I kept this species in cultures for many months. In wet mounts kept in humidity chambers some specimens encysted after some days. Cysts have not been observed by Yoshida et al (2008).
