The role of vision and lateral line sensing for schooling in giant danios (Devario aequipinnatus).

Schooling is a collective behavior that relies on a fish's ability to sense and respond to the other fish around it. Previous work has identified 'rules' of schooling - attraction to neighbors that are far away, repulsion from neighbors that are too close and alignment with neighbors at the correct distance - but we do not understand well how these rules emerge from the sensory physiology and behavior of individual fish. In particular, fish use both vision and their lateral lines to sense each other, but it is unclear how much they rely on information from these sensory modalities to coordinate schooling behavior.

Identification of the trade-off between speed and efficiency in undulatory swimming using a bio-inspired robot.

Anguilliform swimmers, like eels or lampreys, are highly efficient swimmers. Key to understanding their performances is the relationship between the body's kinematics and resulting swimming speed and efficiency. But, we cannot prescribe kinematics to living fish, and it is challenging to measure their power consumption.

Kinematics and behaviour in fish escape responses: guidelines for conducting, analysing and reporting experiments.

Work carried out since the late 1970s has provided key insights into the comparative biomechanics, kinematics, behaviour and neurobiology of fish escape responses. An escape response is an ecologically important behaviour used by fishes to evade predation and aggression via rapid swimming movements. With environmental change expected to affect the physiology and biomechanics of aquatic ectotherms, there is a growing interest in understanding how environmental stressors affect the swimming performance and behaviour of fishes during escape responses, particularly in the context of predator-prey interactions.

Flexibility is a hidden axis of biomechanical diversity in fishes.

Nearly all fish have flexible bodies that bend as a result of internal muscular forces and external fluid forces that are dynamically coupled with the mechanical properties of the body. Swimming is therefore strongly influenced by the body's flexibility, yet we do not know how fish species vary in their flexibility and in their ability to modulate flexibility with muscle activity. A more fundamental problem is our lack of knowledge about how any of these differences in flexibility translate into swimming performance.

Regulation of the swimming kinematics of lampreys Petromyzon marinus across changes in viscosity.

The bodies of most swimming fishes are very flexible and deform as result of both external fluid dynamic forces and internal musculoskeletal forces. If fluid forces change, the body motion will also change unless the fish senses the change and alters its muscle activity to compensate. Lampreys and other fishes have mechanosensory cells in their spinal cords that allow them to sense how their body is bending.

Proprioceptive feedback amplification restores effective locomotion in a neuromechanical model of lampreys with spinal injuries.

Spinal injuries in many vertebrates can result in partial or complete loss of locomotor ability. While mammals often experience permanent loss, some nonmammals, such as lampreys, can regain swimming function, though the exact mechanism is not well understood. One hypothesis is that amplified proprioceptive (body-sensing) feedback can allow an injured lamprey to regain functional swimming even if the descending signal is lost.

Internal vertebral morphology of bony fishes matches the mechanical demands of different environments.

Fishes have repeatedly evolved characteristic body shapes depending on how close they live to the substrate. Pelagic fishes live in open water and typically have narrow, streamlined body shapes; benthic and demersal fishes live close to the substrate; and demersal fishes often have deeper bodies. These shape differences are often associated with behavioral differences: pelagic fishes swim nearly constantly, demersal fishes tend to maneuver near the substrate, and benthic fishes often lie in wait on the substrate.

Swimming kinematics and performance of spinal transected lampreys with different levels of axon regeneration.

Axon regeneration is critical for restoring neural function after spinal cord injury. This has prompted a series of studies on the neural and functional recovery of lampreys after spinal cord transection. Despite this, there are still many basic questions remaining about how much functional recovery depends on axon regeneration.

Biorobotic insights into neuromechanical coordination of undulatory swimming.

Skin sensors on an eel-like robot couple external hydrodynamic pressure with internal neural patterns for robust swimming.

Resilience of neural networks for locomotion.

Locomotion is an essential behaviour for the survival of all animals. The neural circuitry underlying locomotion is therefore highly robust to a wide variety of perturbations, including injury and abrupt changes in the environment. In the short term, fault tolerance in neural networks allows locomotion to persist immediately after mild to moderate injury.

Foretelling the Flex-Vertebral Shape Predicts Behavior and Ecology of Fishes.

Unlabelled: We modeled swimming kinematics and body mechanics of several fish species of varying habitat and body shape based on measurements of internal vertebral morphology.

Synopsis: One key evolutionary innovation that separates vertebrates from invertebrates is the notochord, a central element that provides the stiffness needed for powerful movements. Later, the notochord was further stiffened by the vertebrae, cartilaginous, and bony elements, surrounding the notochord.

Tail Beat Synchronization during Schooling Requires a Functional Posterior Lateral Line System in Giant Danios, Devario aequipinnatus.

Swimming in schools has long been hypothesized to allow fish to save energy. Fish must exploit the energy from the wakes of their neighbors for maximum energy savings, a feat that requires them to both synchronize their tail movements and stay in certain positions relative to their neighbors. To maintain position in a school, we know that fish use multiple sensory systems, mainly their visual and flow sensing lateral line system.

Airfoil-like mechanics generate thrust on the anterior body of swimming fishes.

The anterior body of many fishes is shaped like an airfoil turned on its side. With an oscillating angle to the swimming direction, such an airfoil experiences negative pressure due to both its shape and pitching movements. This negative pressure acts as thrust forces on the anterior body.

Manipulating the perception of time affects voluntary breath-holding duration.

In this study, we examined how time perception, a psychological factor, impacts the physiological response to prolonged, voluntary breath holding. Participants (n = 26) held their breath while watching a distorted timer that made it appear as though time was moving up to 40% faster or slower than real time. We monitored total breath-holding duration under different time manipulation conditions as well as the onset of involuntary breathing movements.

Red muscle activity in bluegill sunfish Lepomis macrochirus during forward accelerations.

Fishes generate force to swim by activating muscles on either side of their flexible bodies. To accelerate, they must produce higher muscle forces, which leads to higher reaction forces back on their bodies from the environment. If their bodies are too flexible, the forces during acceleration could not be transmitted effectively to the environment, but fish can potentially use their muscles to increase the effective stiffness of their body.

Hydrodynamics of linear acceleration in bluegill sunfish, .

In their natural habitat, fish rarely swim steadily. Instead they frequently accelerate and decelerate. Relatively little is known about how fish produce extra force for acceleration in routine swimming behavior.

The role of curvature feedback in the energetics and dynamics of lamprey swimming: A closed-loop model.

Like other animals, lampreys have a central pattern generator (CPG) circuit that activates muscles for locomotion and also adjusts the activity to respond to sensory inputs from the environment. Such a feedback system is crucial for responding appropriately to unexpected perturbations, but it is also active during normal unperturbed steady swimming and influences the baseline swimming pattern. In this study, we investigate different functional forms of body curvature-based sensory feedback and evaluate their effects on steady swimming energetics and kinematics, since little is known experimentally about the functional form of curvature feedback.

Body stiffness and damping depend sensitively on the timing of muscle activation in lampreys.

Unlike most manmade machines, animals move through their world using flexible bodies and appendages, which bend due to internal muscle and body forces, and also due to forces from the environment. Fishes in particular must cope with fluid dynamic forces that not only resist their overall swimming movements but also may have unsteady flow patterns, vortices, and turbulence, many of which occur more rapidly than what the nervous system can process. Has natural selection led to mechanical properties of fish bodies and their component tissues that can respond very quickly to environmental perturbations? Here, we focus on the mechanical properties of isolated muscle tissue and of the entire intact body in the silver lamprey, Ichthyomyzon unicuspis.

The effects of lateral line ablation and regeneration in schooling giant danios.

Fish use multiple sensory systems, including vision and their lateral line system, to maintain position and speed within a school. Although previous studies have shown that ablating the lateral line alters schooling behavior, no one has examined how the behavior recovers as the sensory system regenerates. We studied how schooling behavior changes in giant danios, , when their lateral line system is chemically ablated and after the sensory hair cells regenerate.

Long-axis twisting during locomotion of elongate fishes.

Fish live in a complex world and must actively adapt their swimming behavior to a range of environments. Most studies of swimming kinematics focus on two-dimensional properties related to the bending wave that passes from head to tail. However, fish also twist their bodies three dimensionally around their longitudinal axis as the bending wave passes down the body.

Characterization of the encoding properties of intraspinal mechanosensory neurons in the lamprey.

Proprioceptive sensory inputs are an integral part of the closed-loop system of locomotion. In the lamprey, a model organism for vertebrate locomotion, such sensory inputs come from intraspinal mechanosensory cells called "edge cells". These edge cells synapse directly onto interneurons in the spinal central pattern generator (CPG) circuit and allow the CPG to adjust the motor output according to how the body is bending.

The effect of intrinsic muscular nonlinearities on the energetics of locomotion in a computational model of an anguilliform swimmer.

Animals move through their environments using muscles to produce force. When an animal׳s nervous system activates a muscle, the muscle produces different amounts of force depending on its length, its shortening velocity, and its time history of force production. These muscle forces interact with forces from passive tissue properties and forces from the external environment.

Streamwise vortices destabilize swimming bluegill sunfish (Lepomis macrochirus).

In their natural environment, fish must swim stably through unsteady flows and vortices, including vertical vortices, typically shed by posts in a flow, horizontal cross-flow vortices, often produced by a step or a waterfall in a stream, and streamwise vortices, where the axis of rotation is aligned with the direction of the flow. Streamwise vortices are commonly shed by bluff bodies in streams and by ships' propellers and axial turbines, but we know little about their effects on fish. Here, we describe how bluegill sunfish use more energy and are destabilized more often in flow with strong streamwise vorticity.