Risky Business: Using Physarum polycephalum to Model Comparative Evaluation

Overview

Objectives/Goals Purpose: I used the single cell, multi-nucleate slime mold Physarum polycephalum to model comparative evaluation risk-taking behavior. Physarum were presented with two food sources of varying concentration placed in the light or dark. Physarum are adverse to light; therefore, this experimental design allowed me to determine whether they would choose low-quality food in the dark over high-quality food in the light (a risky choice). Comparative evaluation is a form of decision-making in which assets are weighed based on their pros and cons. Investigative Question: Will Physarum polycephalum choose higher quality foods in a brightly lit, risky environment over lower quality foods in a dark, safe one? Hypothesis: The Physarum will avoid risky environments, even at the cost of foregoing high-quality food. Methods/Materials Materials: Agar, Ground oats, 80 petri dishes, Physarum polycephalum colony, Camera, Black Paper Methods: A Physarum-covered oat flake was placed at the center of a 2% agar dish between two discs of food, each containing a specific percentage concentration of oatmeal, and each 2.5 mm away. The Physarum were offered two concentrations of oatmeal (1% versus 1%, 1% versus 3%, 1% versus 5%, and 1% versus 10%). A control experiment was performed in the dark (n=4 plates/condition). Three risk experiments (n=4/condition) were performed in the light, but with ½ of each plate in the dark. Data were collected at 24, 36 and 48 hours. Results After 48 hours, the Physarum in trials at 1v1 and 1v3 concentrations showed no consistent preference towards the light or dark choice. Only when food quality increased to 1v5 and 1v10 did all Physarum samples move towards the risky, high-quality, food choice. In the dark control, Physarum chose the high quality choice in every situation but in 1v1 moved equally towards both. Conclusions/Discussion My results demonstrate that a 4% or greater difference in food quality caused Physarum to choose the better food, hazarding the risky environment. These data suggest that a complex neurological make-up is not required for an organism to exhibit comparative evaluation.

Competition history

• CSEF 2015 Microbiology (General) · Entry S1527

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