Research

I take on the challenges of studying complex biological designs using integrative approaches, with the ultimate goal of uncovering the interplay between biological and physical principles in evolution. I frame research questions within an evolutionary context, and use both experimental physics and mathematical modeling to obtain answers. 

My research falls into three overlapping areas: (1) Evolution of complex functional systems across cellular to organismal levels. (2) Biophysics, morphogenesis and evolution of novel structure at the cellular and subcellular levels. (3) Ecology and biomechanics of novel performances within contexts of dispersal, feeding and predator-prey interactions. 

General areas: biomechanics, evolution, morphogenesis, physiology, biofluids, behavioral ecology

Specific areas: Biomechanics and evolution of locomotor systems (flapping flight, controlled aerial locomotion, legged locomotion, flagellated locomotion), Interfacial fluid mechanics, Collective motility, Intracellular morphogenesis

Google Scholar | Research Gate


Biomechanics, Evolution & Morphogenesis at Cellular Level


Evolution and morphogenesis of a high-performance intracellular fiber

The hagfishes defend themselves against predators with their slime, a composite material formed within 0.1 second. The strength of slime is imparted by the slime threads, which rival spider silk in strength and are the longest known intracellular fibers (i.e., reaching ~20 cm in length, which is >1,000 times the size of the cell). My ongoing research addresses the development, morphogenesis and evolution of hagfish slime thread by asking: (1) How do the threads develop, coil and package within the cytoplasmic space, and (2) what is the evolutionary origin of slime thread?

Keywords biofiber, evolution, intracellular morphogenesis, predator-prey interaction

Body size-dependent evolution of thread and thread cells: Zeng, Y., Petrichko, S., Nieders, K., Plachetzki, D., Fudge, D. (2021) Evolution of a remarkable intracellular polymer and extreme cell allometry in hagfishes. Current Biology.


Rolling locomotion in bacterial aggregates

I discovered a mode of locomotion built on division-of-labor in the bacterium Caulobacter crescentus. These organisms have two types of cells; immotile stalked cells and flagellated cells. They form aggregates and disperse by rolling on liquid-solid interfaces. I captured images of the rolling aggregates using high-speed microscopy and was able to reconstruct the 3D kinematics for hydrodynamic modeling. C. crescentus wheel-like rolling is driven by flagellar motors and represented by far the smallest wheeled locomotion found in any living systems.

Keywords microorganism movement, hydrodynamics, dispersal, multicellularity, micro-robotics

Zeng, Y. and Liu, B. (2020). Self-propelling and rolling of a sessile-motile aggregate of the bacterium Caulobacter crescentus. Communications biology.


Biomechanics, Evolution & Morphogenesis at Organismal Level


Evolution and biomechanics of insect flight

The earliest winged insects left no trace in the fossil record, yet we know that the first winglets somehow gained size and acquired flapping motion leading to flight. To understand the evolution from winglessness to flapping flight, I examined extant insects undergoing flight reduction. By sampling from intermediate morphologies, I studied how flight biomechanics varied with wing size in evolution.

Evolution and biomechanics of insect flight along ecological gradient

The tropical stick insect Asceles tanarata Brock, 1999 represents one of the few well-documented cases of discrete intra-specific variation in flight-related morphology along an environmental gradient. From lowland Singapore (~50 m) to Cameron Highland (~1600 m), they exhibit a transition from fully-winged to miniaturized winged morphology. My research addresses the evolutionary transitions in flight-related morphology and flight biomechanics in this species group.

Keywords aerodynamics, flight, evolution, sexual dimorphism


Evolution of flight morphology

The stick insects exhibit diverse wing sizes. What is the general pattern of wing size variation and what are the underlying selections? My research showed the variation in wing size depends on sex and correlates with body size. It also explained why there are so few insects with intermediate-sized wings.

Keywords evolution, flight, sexual dimorphism

Zeng, Y., O’Malley, C., Singhal, S., Rahim, F., Park, S., Chen, X., and Dudley, R. (2020). A tale of winglets: evolution of flight morphology in stick insects. Frontiers in Ecology and Evolution.


Biomechanics of aerial righting reflex

Aerial righting maneuver using appendages as aerodynamic surfaces is an essential step in flight evolution. In nymphal stick insect Extatosoma tiaratum, I showed complex leg behaviors with significant aerodynamic utilities for initiating rapid righting rotation and decelerating the rotation afterward. This research demonstrated complex neuromechanical mechanisms can be involved in controlled aerial behaviors as simple as falling upside-down.

Keywords aerodynamics, maneuverability, flight, legs, micro aero-robotics

Zeng, Y., Lam, K., Chen, Y., Gong, M., Xu, Z., and Dudley, R. (2017). Biomechanics of aerial righting in wingless nymphal stick insects. Interface Focus.


Functional implication of the evolution of a novel body plan: Biomechanics of omnidirectional strike in flat spiders

Predator-prey interactions promote the evolution of novel movement capabilities. In a group of spiders with flat bodies and widespread legs, we discovered the ‘omnidirectional strikes,’ where the spiders can attack within 0.12 seconds prey coming from any direction. Such a locomotion system likely evolved to effectively ambush prey on open surfaces, such as rocks and tree trunks, where these spiders commonly hunt. This study has already inspired new studies in biomechanics and robotics.

Keywords maneuverability, legged locomotion, multi-body mechanics

Zeng, Y. and Crews, S. (2018). Biomechanics of omnidirectional strikes in flat spiders. Journal of Experimental Biology.



Collaborative Research

A Minimal Framework for Describing Living Systems

We propose a conceptual approach based on four identified resources—energy, conductance, storage, and information (ECSI)—to reintegrate biological studies with the aim of unifying life sciences under resource limitations. 

Keywords energy, scale, living systems

Caetano-Anollés K., Ewers B., Pavlic T., Seale A., Lucas J., Iyer S., Zeng, Y. (2021) ‘Dealing with varying resources: a metabolic view of life across scales’. Integrative and Comparative Biology.


Ethno-entomology

A first systematic investigation on the entomology of Nuosu (彝) people, a minority group living in mountain villages of southern Sichuan, China.

Keywords ethno-biology


Acknowledgement