BioE PhD Defense Presentation- Harry Tuazon

Advisors: M. Saad Bhamla, Ph.D. (ChBE, Georgia Institute of Technology)

Committee:

Daniel Goldman, Ph.D. (Physics, Georgia Institute of Technology)

David Hu, Ph.D. (ME, Georgia Institute of Technology)

Jorn Dunkel, Ph.D. (Math, Massachusetts Institute of Technology)  

Emily Weigel, Ph.D.  (Biological Sciences, Georgia Institute of Technology)

Physically Entangled Collective Behavior of Aquatic Worm Blobs

California blackworms (Lumbriculus variegatus) form dense, physically entangled structures known as "worm blobs" through chemoattraction, conspecific thigmotaxis, and balancing oxygenation levels. Despite their seemingly stationary nature, these blobs exhibit complex, coordinated behaviors, including rapid transitions between entangled and untangled states. This thesis explores the dynamics of blackworm entanglement and collective behavior through an interdisciplinary approach, combining behavioral biology, active matter physics, and topology. 

First, we examine how dissolved oxygen (DO) levels shape their material-like properties. Worm blobs transition between solid-like and fluid-like states as they adapt to varying DO, forming stable, dense structures in high-oxygen conditions and more fluid configurations in low-oxygen environments. These findings align with behaviors observed in robophysical simulations of “smarticles,” where environmental shifts that impact their internal actuations similarly influence collective properties. We also study the worms' use of helical movements for rapid entanglement and disentanglement, crucial for maintaining cohesion and escaping predators. In interactions with freshwater leeches, blackworms form dense entangled barriers to deter predation, while coordinated helical motions enable swift escape. The leeches’ spiral entombment behavior shows an adaptive predatory strategy to counter this. Furthermore, we reveal emergent behaviors like mucus-mediated particle gathering, with implications for environmental applications such as microplastic collection. The newly identified "worm buoy" behavior showcases how blackworms use surface tension to form floating structures in low-oxygen conditions, enhancing their access to oxygen.

Overall, this study provides insights into physical entanglement, with applications in designing materials and technologies inspired by these collective behaviors. It opens pathways for developing soft entangled swarm robotics and adaptive materials that emulate the resilience and coordination of nature’s systems.