Experience shapes future foraging decisions in a brainless organism

Abstract

The ability to change one’s behaviour based on past experience has obvious fitness benefits. Drawing from past experience requires some kind of information storage and retrieval. The acellular slime mould Physarum polycephalum has previously been shown to use stored information about negative stimuli. Here, we repeatedly exposed the slime mould to three stimuli with differing levels of potential risk: light, salt and lavender. We asked if the slime mould would change its foraging behaviour depending on the level of risk. In our experiment, taking risk yielded better food. We consistently selected individuals that made the same foraging decision (accepting risk or avoiding risk) over multiple trials. Hence, the same individuals were tested over a period of time, but only individuals that continued to make the same decision were allowed to continue. Regardless of selection regime, slime moulds in the light became more likely to select the food in the light over time, while those exposed to salt became more salt averse. Lavender had no effect. Our results can cautiously be interpreted as examples of non-associative learning, adding to a growing body of work showing that the absence of a central nervous system is no impediment to possessing sophisticated information processing.