Biology subjects

Tytell, E. D.

Publications and source records attributed to Tytell, E. D..

8 recordsLinked to original sources

bioRxiv2025

Different functions for the lateral line in schooling behavior in three fish species

Withdrawal StatementThe authors have withdrawn this manuscript because they have found that the gentamicin treatment used to ablate the lateral line was not completely effective in neon tetras and cherry barbs. The results comparing the response to lateral line ablation across those two species may not be valid because the lateral line may not have been fully ablated. Therefore, the authors do not wish this work to be cited. If you have any questions, please contact the corresponding author.

animal behavior and cognition↗

bioRxiv2025

Fast turns are not sped up slow turns: How bluegill sunfish change their kinematics with turn speed

Fish turn extremely often, but this behavior is relatively understudied due to how challenging it can be to get fish to perform such an unsteady maneuver repeatedly. Specifically, little is known about whether fish control turns differently at different turning rates. Here we address the challenge of studying turning by developing a device that elicits turns repeatedly at specific speeds. Using this device, we compare the swimming kinematics of bluegill sunfish (Lepomis macrochirus) during fast and slow turns through 180 degrees. We find that the fish behave differently when turning quickly than when turning slowly: a fast turn is not a sped up slow turn, but is kinematically distinct. In particular, during fast turns, bluegill bend their bodies to minimize moment of inertia before they maximize torque, while in slow turns they maximize torque first, before they bend their bodies. In fast turns, they also beat their pectoral fins at a higher frequency, but take fewer pectoral fin strokes. Differences between the two speed turns may be due to initial momentum and how momentum is conserved throughout the turn, because fast turns have higher initial linear momentum that they can convert into angular momentum to turn around. Summary statementBluegill change how they handle torque and moment of inertia when turning rapidly than when turning slowly. Tradeoffs between linear and angular momentum may play a key role.

animal behavior and cognition↗

bioRxiv2023

Day and night posture of the bluegill sunfish (Lepomis macrochirus)

Many animals assume characteristic postures when resting or sleeping. These postures are often stable and can be maintained passively, thus reducing the energy cost for maintaining an unstable posture. For example, many tetrapods lay prone on the ground and some negatively buoyant fishes are also able to rest on the substrate. Other fishes rest suspended in the water column. Counterintuitively, hovering this way can be of similar energetic cost to swimming. Even if the fish is perfectly neutrally buoyant, any displacement between its center of mass and center of buoyancy will produce destabilizing pitching torques that the fish must constantly work to counteract if they wish to maintain that posture. We hypothesized that a neutrally buoyant fish could rest at an equilibrium - a posture at which no destabilizing torques are produced by the body --to minimize the metabolic costs associated with hovering. Specifically, we studied the bluegill sunfish (Lepomis macrochirus), which is unstable in a horizontal posture. However, by pitching their bodies up or down they may be able to attain a less costly equilibrium posture, one which vertically aligns their center of mass and center of buoyancy. To test this hypothesis, we measured pitch angle of bluegill over the course of 24 hours. We also measured the pitch angles of the body that correspond to stable and unstable equilibria. We found that the stable equilibrium was a belly-up posture, and the unstable equilibrium is a dorsal side up posture pitched 53{+/-}26{degrees} head-down. The fish rested at a head-down pitch of -10.7{+/-}0.4{degrees} degrees, which is significantly steeper than the average pitch during the day of -3.4{+/-}0.8{degrees} degrees head down. These results show that bluegill do not rest at unstable or stable equilibrium. However, they do rest closer to unstable equilibrium at night than during the day. This may allow them to decrease destabilizing torques generated from the relative locations of the COM and COB while maintaining maneuverability.

biophysics↗

bioRxiv2022

Static Stability and Swim Bladder Volume in the Bluegill Sunfish (Lepomis macrochirus)

The static stability of a fish in the water is determined by the relative locations of its center of mass and center of buoyancy. These locations may not be constant, but may depend on the volume of the swim bladder. Changes in swim bladder volume affect both the distribution of mass and the overall volume of the fish, thus affecting the location of the center of mass and center of buoyancy, respectively. To determine the static stability and to examine the influence of the swim bladder on static stability, we used micro-computed tomography to estimate the locations of the center of mass and center of buoyancy in bluegill sunfish (Lepomis macrochrius). In fish oriented head up in the scanner, we found that the center of buoyancy is located 0.441 body lengths from the snout and 0.19 body lengths above the ventral surface of the pelvic girdle, and that the center of mass is 0.0012 BL posterior to and 0.00045 BL ventral to the center of buoyancy. Swim bladders from our specimens ranged in size from 1.9% to 7.6% total body volume, and we found no correlation between swim bladder volume and the distance between the center of mass and center of buoyancy. However, in fish scanned in a head-down orientation, the center of mass is anterior and dorsal to the center of buoyancy--the opposite configuration of that found in fish oriented head up. This change in center of mass and center of buoyancy seems to be caused by changes in the location of the swim bladder in the body: the centroid of the swim bladder is located more posteriorly in fish oriented head-down. The air in the bladder "rises" while heavier tissues "sink," driving a change in tissue distribution and changing the location of the center of mass relative to the center of buoyancy. We conclude that while static stability does not change with swim bladder volume, pitch angle could have a marked effect on static stability.

biophysics↗

bioRxiv2021

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

Neural and functional recovery in lampreys from spinal cord transection has been well documented. However, the extent of axon regeneration is highly variable and it is not known whether it is related to the level of behavioral recovery. To address this, we examined how swimming kinematics were related to axon regeneration by quantifying the relationship between swimming performance and percent axon regeneration of transected lampreys after 11 weeks of recovery. We found that swimming speed was not related to percent axon regeneration but it was closely related to body wave frequency and speed. However, wave frequency and speed varied greatly within individuals which resulted in swimming speed also varying within individuals. In fact, most recovered individuals, regardless of percent axon regeneration, could swim at fast and slow speeds. However, none of the transected individuals were able to generate body waves as large as the control lampreys. In order to swim faster, transected lampreys increased their wave frequencies and, as a result, transected lampreys had much higher frequencies than control lamprey at comparable swimming velocities. These data suggest that the control lampreys swam more efficiently than transected lampreys. In conclusion, there appears to be a minimal recovery threshold in terms of percent axon regeneration required for lampreys to be capable of swimming, however, there also seems to be a limit to how much they can behaviorally recover.

animal behavior and cognition↗

bioRxiv2020

The fish body functions as an airfoil: surface pressures generate thrust during carangiform locomotion

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. Here, we apply a high-resolution, pressure-based approach to describe how two fishes, bluegill sunfish (Lepomis macrochirus Rafinesque) and brook trout (Salvelinus fontinalis Mitchill), swimming in the carangiform mode, the most common fish swimming mode, generate thrust on their anterior bodies using leading-edge suction mechanics, much like an airfoil. These mechanics contrast with those previously reported in lampreys - anguilliform swimmers - which produce thrust with negative pressure but do so through undulatory mechanics. The thrust produced on the anterior body of these carangiform swimmers through negative pressure comprises 28% of the total thrust produced over the body and caudal fin, substantially decreasing the net drag on the anterior body. On the posterior region, subtle differences in body shape and kinematics allow trout to produce more thrust than bluegill, suggesting that they may swim more effectively. Despite the large phylogenetic distance between these species, and differences near the tail, the pressure profiles around the anterior body are similar. We suggest that such airfoil-like mechanics are highly efficient, because they require very little movement and therefore relatively little active muscular energy, and may be used by a wide range of fishes since many species have appropriately-shaped bodies. Significance StatementMany fishes have bodies shaped like a low-drag airfoil, with a rounded leading edge and a smoothly tapered trailing region, and move like an airfoil pitching at a small angle. This shape reduces drag but its significance for thrust production by fishes has not been investigated experimentally. By quantifying body surface pressures and forces during swimming, we find that the anterior body shape and movement allows fishes to produce thrust in the same way as an oscillating airfoil. This work helps us to understand how the streamlined body shape of fishes contributes, not only to reducing drag, but also directly to propulsion, and, by quantitatively linking form and function, leads to a more complete understanding fish evolution and ecology.

physiology↗

bioRxiv2018

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 cannot be transmitted effectively to the environment. Here, we investigate whether fish can use their red muscle to stiffen their bodies during acceleration. We used high-speed video, electromyographic recordings, and a new digital inertial measurement unit to quantify body kinematics, red muscle activity, and 3D orientation and centre of mass acceleration during forward accelerations and steady swimming over several speeds. During acceleration, fish co-activated anterior muscle on the left and right side, and activated all muscle sooner and kept it active for a larger fraction of the tail beat cycle. These activity patterns are consistent with our hypothesis that fish use their red muscle to stiffen their bodies during acceleration. We suggest that during impulsive movements, flexible organisms like fishes can use their muscles not only to generate propulsive power but to tune the effective mechanical properties of their bodies, increasing performance during rapid movements and maintaining flexibility for slow, steady movements.

biophysics↗

bioRxiv2018

Hydrodynamics of linear acceleration in bluegill sunfish Lepomis macrochirus

SUMMARY STATEMENTBluegill sunfish accelerate primarily by increasing the total amount of force produced in each tail beat but not by substantially redirecting forces.\n\nABSTRACTIn 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. In this study, we examined the flow around bluegill sunfish Lepomis macrochirus during steady swimming and during forward acceleration, starting at a range of initial swimming speeds. We found that bluegill produce vortices with higher circulation during acceleration, indicating a higher force per tail beat, but do not substantially redirect the force. We quantified the flow patterns using high speed video and particle image velocimetry and measured acceleration with small inertial measurement units attached to each fish. Even in steady tail beats, the fish accelerates slightly during each tail beat, and the magnitude of the acceleration varies. In steady tail beats, however, a high acceleration is followed by a lower acceleration or a deceleration, so that the swimming speed is maintained; in unsteady tail beats, the fish maintains the acceleration over several tailbeats, so that the swimming speed increases. We can thus compare the wake and kinematics during single steady and unsteady tailbeats that have the same peak acceleration. During unsteady tailbeats when the fish accelerates forward for several tailbeats, the wake vortex forces are much higher than those at the same acceleration during single tailbeats in steady swimming. The fish also undulates its body at higher amplitude and frequency during unsteady tailbeats. These kinematic changes likely increase the fluid dynamic added mass of the body, increasing the forces required to sustain acceleration over several tailbeats. The high amplitude and high frequency movements are also likely required to generate the higher forces needed for acceleration. Thus, it appears that bluegill sunfish face a tradeoff during acceleration: the body movements required for acceleration also make it harder to accelerate.

biophysics↗