Not 100% sure. Fairly new to slime molds, but this looks like a good fit.
Alder leaf for size
Protozoa are a diverse group of unicellular eukaryotic organisms, many of which are motile. Originally, protozoa had been defined as unicellular protists with animal-like behavior, e.g., movement. Protozoa were regarded as the partner group of protists to protophyta, which have plant-like behaviour, e.g. photosynthesis.