Research

Hsieh Lab | Temple University | Department of Biology | Philadelphia, PA 19122 | USA

In the natural world where the properties of a surface can vary dramatically between steps, the locomotor system must be able to respond rapidly and effectively to these environmental challenges. Our long-term research objective is to understand how animals respond to and manipulate naturally unstable and unpredictable environments to facilitate their daily locomotion. We approach our research in an interdisciplinary manner, using a combination of techniques and concepts inspired by other disciplines as diverse as ecology, evolution, behavior, engineering, and computer science. We combine fieldwork with laboratory experimentation to achieve a holistic understanding for our questions while placing our theories and results in a context relevant to the ecology and evolution of the organism.

Our research addresses two major themes:

1) how unpredictable or unstable surface properties affect locomotor behavior and control; and

2) how ecology and habitat structure influence morphological evolution.

Current ongoing projects include:

    The multi-functional foot and its role in locomotor control on complex media

Basilisk lizard foot

The effectiveness with which an animal moves through its natural environment is critically important to its survival. Yet, how stability is achieved remains poorly understood. Natural materials can be extremely complex, at times solidifying and at other times flowing during a single step. With this project, we are striving to understand how the geometry, morphology, and kinematics of foot use drive foot-substrate interactions, and the roles they play in achieving smooth locomotion on complex terrain.

In the lab:
Mike Fath (research assistant), Liz Tucker (Kinesiology masters student)

Collaborators:
Temple University: Mathematics: Daniel Szyld (PI), and Jose Garay (graduate student)
                           Computer and Information Science: Rolf Lakaemper (PI)
Tufts University: Eric Tytell (PI)
University of Nevada, Las Vegas: David Lee (PI)
Georgia Institute of Technology: Daniel Goldman (PI)

Li, C, Hsieh, ST, and Goldman, DI. (2012). Multi-functional foot use during running in the zebra-tailed lizard (Callisaurus draconoides) J Exp Biol 215: 3293-3308.

    Effects of limb autotomy and regeneration on locomotion

Orange baboon tarantulas

While limb amputation is a very disruptive event for humans, it turns out that many arthropods are capable of losing, and regenerating, their primary locomotor appendages. Limb autotomy, or the voluntary amputation of an appendage, occurs regularly among two of our study organisms: tarantulas and crabs. We are determining how the loss and regeneration of limbs affect locomotor control strategy, learning, and mechanisms of adaptation.

In the lab:

Janne Pfeiffenberger (graduate student), Kyle Hovey (research assistant)

Collaborators:

Temple University, Bioengineering: Andrew Spence (PI), Simon Wilshin (post-doc)

Cornell University (Ron Hoy's Lab): Paul Shamble (graduate student)

    Original and regenerated tail function during locomotion in anole lizards

Lizards are known for their ability to autotomize (i.e. drop) their tail and then regenerate it. However, unlike the original, multi-segmented tail, the regenerated tail consists of a single cartilaginous rod. Previous studies by other labs have shown that the lizard's tail can be important for counteracting perturbations and can affect performance and maneuverability on level ground. We are exploring how the loss of the tail and the subsequently regenerated tail affects the locomotor stability, performance, and mechanics of running. Furthermore, we are quantifying the material properties of the original and regenerated tail to understand how its properties affect its movement. See here for an abstract of a tail presented at the Robotics Science and Systems 2015 Workshop on Robotic Uses for Tails.

    Running anole lizard

Collaborators:

Arizona State University: Kenro Kusumi, Rebecca Fisher (also University of Arizona), Jeanne Wilson-Rawls

    Gait transitions when moving from water to land in turtles

The transition from water to land was a major evolutionary event in vertebrate history that resulted in an explosion of diversity as tetrapods radiated into available terrestrial niches. Yet, what constraints and challenges these early tetrapods encountered, and how they dealt with these challenges have been difficult to address since these are only represented by fossilized materials. Turtles are an environmentally diverse group of reptiles, with species specialized for fully terrestrial (e.g., desert tortoises and box turtles), semi-aquatic (e.g., red-eared sliders and mud turtles), and aquatic (e.g., sea turtles and pig-nosed turtles) lifestyles. We are using turtles as an extant model system to understand the strategies they use for transitioning between these two very different environments, and to also elucidate the challenges they encounter when placed in an unfamiliar environment.

In the lab:

Nicole Mazouchova(graduate student), Amber Dai (summer research intern)

Collaborators:

Royal Veterinary College, University College London: Simon Wilshin (post-doc)

    Target-driven control of foot placement in cellar spiders

Spider on complex surface

Spiders routinely crawl around on webs and complex terrain, both which have limited footholds. Yet, preliminary results suggest that spiders are not actually using a follow-the-leader gait when moving on flat, level ground. A follow-the-leader gait is a specific foot placement pattern in which the more posterior feet use footholds occupied by more anterior feet, and can thereby simplify the control required to ensure the foot is placed on a secure foothold. We are using cellar spiders as a model system for exploring the role of various sensory modalities for achieving accurate foot placement when the placement options are limited.

In the lab:

Undergraduates: Larry Gardner and Alina Gawlinski

    The evolution of terrestriality in the Pacific leaping blenny.

Alticus arnoldorum in a burrowWay back in 2002, I began studying a small marine fish, the Pacific leaping blenny (Alticus arnoldorum). This fish lives in the violent intertidal zone of the tropical Pacific Ocean, and is particularly unique in that it seldom ever enters the water. In fact, in all the years I have worked with this fish in the field, I have only once seen one individual on a particularly hot day temporarily submerge itself in a small pool. On land, these fish feed, breed, and even defend terrestrial territories. When chased by marauding researchers, these fish prefer to climb up a rock face and into a crevice above water rather than submerge itself and swim away.

These fish serve as an ideal model for exploring the challenges and constraints faced by early vertebrates during one of the most pivotal paleontological events: the transition from water to land. My previous work has shown that these fish can leap several body lengths on land,Peeking out of a crack above water... climb vertical surfaces, and porpoise across the water surface at extremely high velocities.Their extreme terrestriality may be attributable to a locomotor innovation (Hsieh, 2010). Unlike other fish that can only move their tail side-to-side, when moving on land, these blennies curl their body into a C-shape, then twist their tail axially, and push off the ground with the side of their tail. This appears to afford them greater stability than the "normal" fish, so that they are able to perform incredibly acrobatic and controlled leaps and hops on land. However, because they still require water to breathe through their skin (and their gills when underwater), their activity periods on land are still highly-constrained by tide cycles and temperature variations (Ord and Hsieh, 2011). Ongoing research includes teasing apart the molecular phylogenetic relationships of closely-related genera and determining how much morphological and physiological diversification was necessary for such a drastic environmental transition.

Hsieh, S. T. (2010). A locomotor innovation enables water-land transition in a marine fish. PLoS One 5(6): e11197.

Ord, T.J. and Hsieh, S.T. (2011). A highly social, land-dwelling fish defends territories in a constantly fluctuating environment. Ethology. 117(10):918-927.

Gibb AC, Ashley-Ross M, Hsieh ST (2013). Thrash, flip, or jump: the behavioral and functional continuum of terrestrial locomotion in teleost fishes. Integrative and Comparative Biology. Advance Access. doi:10.1093/icb/ict052

    Locomotor control and recovery from slipping during bipedal running in lizards.

Bipedally running frilled dragonThe natural world is filled with unpredictable surfaces that may shift or flow when stepped on. In fact, injuries due to slips and falls in the elderly are a leading cause of morbidity and mortality among the elderly population, making this also a major public health concern. We are using bipedally-running lizards to understand the interaction of passive and active control mechanisms in play during an unexpected slip perturbation and while running on granular media. Our results will allow us to reliably predict when a perturbation has a greater likelihood of leading to a fall, and help develop solutions for decreasing falling risk on a daily basis.

    Effects of inverted running on center of mass dynamics in cockroaches

Upside-down running cockroachThe classic biomechanical model for running is the SLIP (spring-loaded inverted pendulum) model. This model consists of a mass mounted atop a linear spring, and in such a simple form can accurately predict the center of mass dynamics of a multi-legged organism while running. One of the implicit assumptions of this model, however, is that the gravitational vector is always oriented such that it acts to compress the leg spring. Using empirical and mathematical modeling techniques, we are now exploring whether this model still applies when running upside-down.

Lab members: Frank Nelson

In addition to our ongoing research projects, we also prioritize our involvement in citizen science. In collaboration with the Kulathinal lab, we are creating a web-based resource named lizardbase (poster), which we hope will serve as a central depository for lizard-related research data, as well as a globally-collaborative educational resource for K-12 students.