Document Type
Dissertation
Date of Award
8-31-2022
Degree Name
Doctor of Philosophy in Biology - (Ph.D.)
Department
Federated Department of Biological Sciences
First Advisor
Simon J. Garnier
Second Advisor
Horacio G. Rotstein
Third Advisor
Gareth J. Russell
Fourth Advisor
Gregory F. Weber
Fifth Advisor
David L. Hu
Abstract
Evolutionary pressures to improve fitness, have enabled living systems to make adaptive decisions when faced with heterogeneous and changing environmental and physiological conditions. This dissertation investigated the mechanisms of how environmental and physiological factors affect the behaviors of non-neuronal organisms. The acellular slime mold Physarum polycephalum was used as the model organism, which is a macroscopic, unicellular organism, that self-organizes into a network of intersecting tubules. Without using neurons, P. polycephalum can solve labyrinth mazes, build efficient tubule networks, and make adaptive decisions when faced with complicated trade-offs, such as between food quality and risk, speed and accuracy, and exploration and exploitation. However, the understanding of the mechanisms used by P. polycephalum in exhibiting such behaviors is very limited. Therefore, the objective of this dissertation is to understand the mechanisms adopted by non-neuronal organisms to explore and exploit resources in the physical environment, using environmental and physiological information.
To this end, the dissertation characterizes the direction and amount of influence between different regions of tubule-shaped P. polycephalum cells in binary food choice experiments. The results show that when the two food sources are identical in quality, the regions near the food source act as the drivers of P. polycephalum tubule behavior. Conversely, when one of the food sources is more enriched with nutrients, the regions near the rejected food source were found to drive the tubule behavior. Secondly, a generalized choice-making criterion was formulated to determine the choice-making behaviors of P. polycephalum, examine whether sufficient experimental time was given to make a choice, and determine the time point at which a choice was made. The criterion was tested on binary food choice experiments using P. polycephalum tubules. The results show that P. polycephalum made a choice for the option for the better food option, except when the differences in food quality were low. Moreover, the criterion was found to not determine the choice-making behaviors when the food sources presented were identical in quality. Thirdly, the dissertation investigated whether P. polycephalum cells modify their future exploratory behavior using their past foraging experience. The results did not find a strong influence of the past foraging experience on the exploratory networks formed by P. polycephalum cells. Finally, P. polycephalum exploratory behaviors were examined and compared when the cells were in high-energy versus low-energy physiological conditions. Interestingly, the study found the P. polycephalum cells in low-energy conditions show an increased tendency to split themselves into multiple autonomous cells. Additionally, the behavior is shown to increase the fitness of the cell by increasing its foraging efficiency.
Recommended Citation
Ray, Subash Kusum, "Brainless but smart: Investigating cognitive-like behaviors in the acellular slime mold physarum polycephalum" (2022). Dissertations. 1627.
https://digitalcommons.njit.edu/dissertations/1627
