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Flammang, Brooke

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Flammang

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Brooke

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Flammang, Brooke

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    Caudal fin shape modulation and control during acceleration, braking and backing maneuvers in bluegill sunfish, Lepomis macrochirus
    (The Company of Biologists, 2008) Flammang, Brooke; Lauder, George
    Evolutionary patterns of intrinsic caudal musculature in ray-finned fishes show that fine control of the dorsal lobe of the tail evolved first, followed by the ability to control the ventral lobe. This progression of increasing differentiation of musculature suggests specialization of caudal muscle roles. Fine control of fin elements is probably responsible for the range of fin conformations observed during different maneuvering behaviors. Here, we examine the kinematics of the caudal fin and the motor activity of the intrinsic caudal musculature during kick-and-glide, braking and backing maneuvers, and compare these data with our previous work on the function of the caudal fin during steady swimming. Kick-and-glide maneuvers consisted of largeamplitude, rapid lateral excursion of the tail fin, followed by forward movement of the fish with the caudal fin rays adducted to reduce surface area and with the tail held in line with the body. Just before the kick, the flexors dorsalis and ventralis, hypochordal longitudinalis, infracarinalis and supracarinalis showed strong activity. During braking, the dorsal and ventral lobes of the tail moved in opposite directions, forming an ʻSʼ-shape, accompanied by strong activity in the interradialis muscles. During backing up, the ventral lobe initiated a dorsally directed wave along the distal edge of the caudal fin. The relative timing of the intrinsic caudal muscles varied between maneuvers, and their activation was independent of the activity of the red muscle of the axial myomeres in the caudal region. There was no coupling of muscle activity duration and electromyographic burst intensity in the intrinsic caudal muscles during maneuvers, as was observed in previous work on steady swimming. Principal-component analysis produced four components that cumulatively explained 73.6% of the variance and segregated kick-and-glide, braking and backing maneuvers from each other and from steady swimming. The activity patterns of the intrinsic caudal muscles during maneuvering suggest motor control independent from myotomal musculature, and specialization of individual muscles for specific kinematic roles.
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    Speed-dependent intrinsic caudal fin muscle recruitment during steady swimming in bluegill sunfish, Lepomis macrochirus
    (The Company of Biologists, 2008) Flammang, Brooke; Lauder, George
    There are approximately 50 muscles that control tail fin shape in most teleost fishes, and although myotomal muscle function has been extensively studied, little work has been done on the intrinsic musculature that controls and shapes the tail. In this study we measured electrical activity in intrinsic tail musculature to determine if these muscles are active during steady rectilinear locomotion, and to compare intrinsic muscle recruitment patterns to previous data on myotomal muscle fibers. Five bluegill sunfish (Lepomis macrochirus) were anaesthetized and electrode wires surgically placed into a total of 24 intrinsic caudal muscles, up to 13 at a time, and activity was correlated with synchronous recordings from myotomal fibers in the caudal peduncle. After recovery, fish swam steadily at speeds of 0.5, 1.2 and 2.0·L·s–1, while filmed from lateral, posterior and ventral views simultaneously at 250·frames·s–1. Comparison among speeds confirmed that muscle recruitment varies significantly with speed. At 0.5·L·s–1, the caudal fin was generally not used for propulsion, and swimming was accomplished primarily through body undulations. Intrinsic caudal muscle activity at this speed was intermittent and variable. At 1.2 and 2.0·L·s–1, the supracarinalis and infracarinalis muscles acted on the dorsal- and ventral-most fin rays, respectively, to expand the surface area of the caudal fin. The interradialis muscles adducted individual fin rays, dorsally to ventrally, following activation of the hypochordal longitudinalis. Contralateral muscle activity of interradialis muscles occurred as the caudal fin crossed the mean direction of travel and fin height was greatest, whereas ipsilateral activity of carinalis muscles occurred near points of maximum excursion of the fin, at speeds of 1.2 and 2.0·L·s–1, after fin height was lowest. Burst intensity increased with swimming speed, suggesting stiffening of the tail fin against imposed hydrodynamic loads. Activity patterns of intrinsic caudal muscles suggest that these most posterior muscles in fishes, located within the tail, are among the very first recruited as swimming speed increases, and that slow undulatory swimming is powered by muscle fibers located posteriorly in the caudal peduncle and tail.
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    A robotic fish caudal fin: effects of stiffness and motor program on locomotor performance
    (The Company of Biologists, 2011) Esposito, C. J.; Tangorra, J. L.; Flammang, Brooke; Lauder, George
    We designed a robotic fish caudal fin with six individually moveable fin rays based on the tail of the bluegill sunfish, Lepomis macrochirus. Previous fish robotic tail designs have loosely resembled the caudal fin of fishes, but have not incorporated key biomechanical components such as fin rays that can be controlled to generate complex tail conformations and motion programs similar to those seen in the locomotor repertoire of live fishes. We used this robotic caudal fin to test for the effects of fin ray stiffness, frequency and motion program on the generation of thrust and lift forces. Five different sets of fin rays were constructed to be from 150 to 2000 times the stiffness of biological fin rays, appropriately scaled for the robotic caudal fin, which had linear dimensions approximately four times larger than those of adult bluegill sunfish. Five caudal fin motion programs were identified as kinematic features of swimming behaviors in live bluegill sunfish, and were used to program the kinematic repertoire: flat movement of the entire fin, cupping of the fin, W-shaped fin motion, fin undulation and rolling movements. The robotic fin was flapped at frequencies ranging from 0.5 to 2.4Hz. All fin motions produced force in the thrust direction, and the cupping motion produced the most thrust in almost all cases. Only the undulatory motion produced lift force of similar magnitude to the thrust force. More compliant fin rays produced lower peak magnitude forces than the stiffer fin rays at the same frequency. Thrust and lift forces increased with increasing flapping frequency; thrust was maximized by the 500 stiffness fin rays and lift was maximized by the 1000 stiffness fin rays.
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    Pectoral fins aid in navigation of a complex environment by bluegill sunfish under sensory deprivation conditions
    (The Company of Biologists, 2013) Flammang, Brooke; Lauder, George
    Complex structured environments offer fish advantages as places of refuge and areas of greater potential prey densities, but maneuvering through these environments is a navigational challenge. To successfully navigate complex habitats, fish must have sensory input relaying information about the proximity and size of obstacles. We investigated the role of the pectoral fins as mechanosensors in bluegill sunfish swimming through obstacle courses under different sensory deprivation and flow speed conditions. Sensory deprivation was accomplished by filming in the dark to remove visual input and/or temporarily blocking lateral line input via immersion in cobalt chloride. Fish used their pectoral fins to touch obstacles as they swam slowly past them under all conditions. Loss of visual and/or lateral line sensory input resulted in an increased number of fin taps and shorter tap durations while traversing the course. Propulsive pectoral fin strokes were made in open areas between obstacle posts and fish did not use the pectoral fins to push off or change heading. Bending of the flexible pectoral fin rays may initiate an afferent sensory input, which could be an important part of the proprioceptive feedback system needed to navigate complex environments. This behavioral evidence suggests that it is possible for unspecialized pectoral fins to act in both a sensory and a propulsive capacity.