A spikey microball - Actinophrys sol

"Come wiggle through my spines" said the Actinophrys to the Stylonychia "and maybe I'll invite you to dinner."

This unknown is Actinophrys sol, a heliozoan. Heliozoans are the so called "sunburst animals" of early microscopists. Of course, they are not animals at all, but single-celled protists common in many ponds.

Until recently, heliozoans have been classified with the amoebas, and indeed they do use the amoeba-like style of phagocytosis for engulfing prey trapped by their spines. However, exactly where they fit on the tree of life is now being investigated using new and revealing techniques of molecular biology. Preliminary findings suggest that heliozoans are on a branch of their own.

The two individuals shown have just come out of a cyst collected from a dried up rain puddle in the Arizona desert. But what is that glob of greenish material? Was it part of the cyst? Was it a last meal before the pond dried up. Did cell division take place during encystment? Did two individuals encyst together? These are questions to investigate the next time we visit that temporary pool and pick up another dried mud chip.