Watch as these two microscopic, single-celled protozoans (protists), battle it out, resulting in one eating the other. These organisms inhabit almost any body of still water (ponds, lakes, reservoirs) and the oceans, and are the most important consumers of bacteria in the world.
In the video, you can see Euplotes sp. creating water currents with its finger-like cirri. These currents bring bacteria, the occasional Tetrahymena, and other smaller organisms (e.g. algae) into its oral groove (the equivalent of its mouth), and that is how it eats.
Duke University biologist Jean Philippe Gibert explains: “Despite their small size, there is twice as much protist biomass in the world as there is animal biomass. Meaning that if you were to add up all the lions, zebras, elephants, spiders, whales, etc., and weigh them, and do the same for all of these single-celled little fellas, you'd get twice as much weight from the aggregated cells than you would from all animals combined.”