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Abstract Many organisms utilize group aggregation as a method for survival. The freshwater oligochaete, Lumbriculus variegatus (California blackworms) form tightly entangled structures, or worm “blobs”, that have adapted to survive in extremely low levels of dissolved oxygen (DO). Individual blackworms adapt to hypoxic environments through respiration via their mucous body wall and posterior ciliated hindgut, which they wave above them. However, the change in collective behavior at different levels of DO is not known. Using a closed-loop respirometer with flow, we discover that the relative tail reaching activity flux in low DO is ∼75x higher than in the high DO condition. Additionally, when flow rate is increased to suspend the worm blobs upward, we find that the average exposed surface area of a blob in low DO is ∼1.4x higher than in high DO. Furthermore, we observe emergent properties that arise when a worm blob is exposed to extreme DO levels. We demonstrate that internal mechanical stress is generated when worm blobs are exposed to high DO levels, allowing them to be physically lifted off from the bottom of a conical container using a serrated endpiece. Our results demonstrate how both collective behavior and the emergent generation of internal mechanical stress in worm blobs change to accommodate differing levels of oxygen. From an engineering perspective, this could be used to model and simulate swarm robots, self-assembly structures, or soft material entanglements.
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Flotation of aquatic worms and other hyponeuston
The California blackworm,Lumbriculus variegatus, lives underwater and latches its tail to the water surface for respiration and stability. Little is known about the upward force generated by this posture. In this combined experimental and theoretical study, we visualize the menisci shape for blackworms and blackworm mimics, composed of smooth and corrugated epoxy rods. We apply previous theoretical models for floating cylinders to predict the upward force and safety factor of blackworms as well as other organisms such as mosquito larvae, leeches and aquatic snails. Understanding the upward forces of organisms that latch onto the water surface may help to understand the evolution of interfacial attachment and inspire biomimetic robots.
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- PAR ID:
- 10598655
- Publisher / Repository:
- Royal Society Interface
- Date Published:
- Journal Name:
- Interface Focus
- Volume:
- 15
- Issue:
- 2
- ISSN:
- 2042-8901
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1098/rsfs.2024.0057
