A soil-dwelling amoeba which grazes on bacteria could be the world's smallest farmer.
Scientists have learned that some of the single-celled organisms display a primitive form of agriculture.
Instead of consuming all the bacteria at a particular site, they save some to "seed" at other locations where food is scarce.
About a third of the amoebae studied performed the role of "farmers", said the researchers writing in the journal Nature.
The amoeba species Dictyostelium discoideum lives in slime moulds in the soil, where tens of thousands of the organisms aggregate together to form a moving multicelled "slug".