Testate Rhizopods

Amoeba come in a wide variety of shapes and sizes. The bog-standard, free-range amoeba glides wherever its pseudopodia take it, going with the flow of its protoplasm (see movie). Heliozoans – amoeba with spines (see earlier post) – roll trough the water. A third form, testate rhizopods pictured here, secrete a glassy shell for themselves, that reminds me of a hot-air balloon or a Greek amphora, and send their pseudopodium ('false feet') out from the opening to engulf anything that’s smaller than themslves and within reach. The upper testate rhizopod here is alive, with an amoeba inside the shell. The yellowish objects within are partially digested small algae or diatoms that it’s grabbed. The image below is of an empty testa, this one with spines and showing the surface patterning on its glassy surface. Different species can be recognised by their testa pattern. They are both about one tenth of a millimetre long and were photographed with a simple microscope, without any fancy optical tricks. They came from a boggy spring in Teesdale.