Body Form, Locomotion and Foraging in Aquatic Vertebrates

Four functional categories are denned to embrace the range oflocomotor diversity of aquatic vertebrates; (1) body/caudalfin (BCF) periodic propulsion where locomotor movements repeat,as occurs in cruising and sprint swimming; (2) BCF transientpropulsion where kinematics are brief and non-cylic, as occursin fast-starts and powered turns; (3) median and paired fin(MPF) propulsion, with very diverse fin kinematics, used inslow swimming and precise maneuver; (4) occasional propulsionor "non-swimming." Specialization in any one of these categoriescompromises performance in one or more of the others, therebyreducing locomotor diversity and hence behavioral options. Foodcharacteristics influencing the role of locomotion in searchand capture are; (1) distribution in space and/or time and (2)evasive capabilities. BCF periodic swimmers take food that iswidely dispersed in space/time; BCF transient swimmers consumelocally abundant evasive items and MPF swimmers consume non-evasivefood in structurally complex habitats. Locomotor specialistsunder-utilize smaller food items in exposed habitats. This resourceis exploited by smaller fish, which are locomotor generalistsbecause of predation pressures. For such locomotor generalists,locomotor adaptations for food capture are of diminished importanceand other adaptations such as suction and protrusible jaws infish are common.     

Design and Implementation of Paired Pectoral Fins Locomotion of Labriform Fish Applied to a Fish Robot

In present,there are increasing interests in the research on mechanical and control system of underwater vehicles.Theseongoing research efforts are motivated by more pervasive applications of such vehicles including seabed oil and gas explorations,scientific deep ocean surveys,military purposes,ecological and water environmental studies,and also entertainments.However,the performance of underwater vehicles with screw type propellers is not prospective in terms of its efficiency andmaneuverability.The main weaknesses of this kind of propellers are the production of vortices and sudden generation of thrustforces which make the control of the position and motion difficult.On the other hand,fishes and other aquatic animals are efficient swimmers,posses high maneuverability,are able to followtrajectories,can efficiently stabilize themselves in currents and surges,create less wakes than currently used underwater vehicle,and also have a noiseless propulsion.The fish’s locomotion mechanism is mainly controlled by its caudal fin and paired pectoralfins.They are classified into Body and/or Caudal Fin(BCF)and Median and/or paired Pectoral Fins(MPF).The study of highlyefficient swimming mechanisms of fish can inspire a better underwater vehicles thruster design and its mechanism.There are few studies on underwater vehicles or fish robots using paired pectoral fins as thruster.The work presented in thispaper represents a contribution in this area covering study,design and implementation of locomotion mechanisms of pairedpectoral fins in a fish robot.The performance and viability of the biomimetic method for underwater vehicles are highlightedthrough in-water experiment of a robotic fish.     

Function of the medial red muscle during sustained swimming in common thresher sharks: Contrast and convergence with thunniform swimmers

Through convergent evolution tunas and lamnid sharks share thunniform swimming and a medial position of the red, aerobic swimming musculature. During continuous cruise swimming these muscles move uniformly out of phase with local body curvature and the surrounding white muscle tissue. This design results in thrust production primarily from the caudal fin rather than causing whole-body undulations. The common thresher shark (Family Alopiidae) is the only other fish known to share the same medial red muscle anatomy as the thunniform swimmers. However, the overall body shape and extremely heterocercal caudal fin of the common thresher is not shared with the thunniform swimmers, which have both fusiform bodies and high aspect-ratio, lunate caudal fins. Our study used sonomicrometry to measure the dynamics of red and white muscle movement in common thresher sharks swimming in the ocean to test whether the medial position of red muscle is associated with uncoupling of muscle shortening and local body bending as characteristic of thunniform swimmers. Common threshers (～ 60–100 kg) instrumented with sonomicrometric and electromyographic (EMG) leads swam alongside of the vessel with a tail-beat frequency of ～ 0.5 Hz. EMG signals confirmed that only the red muscle was active during sustained swimming. Despite the more medial position of the red muscle relative to the white muscle, its strain was approximately 1.5-times greater than that of the overlying white muscle, and there was a notable phase shift between strain trajectories in the red muscle and adjacent white muscle. These results suggest an uncoupling (shearing) of the red muscle from the adjacent white muscle. Although the magnitude of the phase shift between red and white muscle strain was relatively constant within individuals, it varied among sharks, ranging from near zero (red and white in phase) to almost 180° out of phase. This extent in variability has not been documented previously for thunniform swimmers with a medial red muscle position and may be a characteristic of the thresher's unique body and caudal fin morphology. Nonetheless, the uncoupling of red and white muscle strain remains a consistent character associated with fishes having a medially positioned red muscle.     

Parametric Study of an Underwater Finned Propulsor Inspired by Bluespotted Ray

The performance of bluespotted rays was emulated in the design of a bioinspired underwater propulsor in the present work.First,the movement of a live bluespotted ray was captured for the swimming mode and useful information to the biomimetic mechanism design.By virtue of the modular and reeonfigurable design concept,an undulatory fin propulsion prototype was developed.With a proper experimental set-up,orthogonal experiments were conducted to investigate the effect of various fin design parameters on the propulsion speed,thrust,and power of the fish robot.The controllable fin parameters include frequency,amplitude,wavelength,fm shape,and undulatory mode.The significance of these parameters was also determined by using the variance analysis.The results demonstrate that the designed propulsor,imitating bluespotted rays with large expanded undulatory fins,is able to propel itself by changing various kinematic parameters.     

Polymorphism and multiple correlated characters: Do flatfish asymmetry morphs also differ in swimming performance and metabolic rate?

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An interspecific comparison between morphology and swimming performance in cyprinids

Flow regimes are believed to be of major evolutionary significance in fish. The flow regimes inhabited by cyprinids vary extensively from still flow regimes to riptide flow regimes. To test (i) whether flow‐driven swimming performance and relevant morphological differentiation are present among fish species and (ii) whether evolutionary shifts between high‐flow and low‐flow habitats in cyprinids are associated with evolutionary trade‐offs in locomotor performance, we obtained data on both steady and unsteady swimming performance and external body shape for 19 species of cyprinids that typically occur in different flow regimes (still, intermediate and riptide). We also measured the routine energy expenditure (RMR) and maximum metabolic rate (MMR) and calculated the optimal swimming speed. Our results showed that fish species from riptide groups tend to have a higher critical swimming speed (U_crit), maximum linear velocity (V_max) and fineness ratio (FR) than fish from the other two groups. However, there was no correlation between the reconstructed changes in the steady and unsteady swimming performance of the 19 species. According to the phylogenetically independent contrast (PIC) method, the U_crit was actively correlated with the MMR. These results indicated that selection will favour both higher steady and unsteady swimming performance and a more streamlined body shape in environments with high water velocities. The results suggested that steady swimming performance was more sensitive to the flow regime and that for this reason, changes in body shape resulted more from selective pressure on steady swimming performance than on unsteady swimming performance. No evolutionary trade‐off was observed between steady and unsteady swimming performance, although U_crit and MMR were found to have coevolved. However, a further analysis within each typically occurring habitat group suggested that the trade‐off that may exist between steady and unsteady swimming performance may be concealed by the effect of habitat.     

Repeat UCrit and endurance swimming in juvenile shortnose sturgeon (Acipenser brevirostrum)

Previous results show that juvenile shortnose sturgeon are steady swimmers and, compared with salmonids, generally have low critical swimming (UCrit) and endurance swimming capacities. Most studies on swimming capacities of sturgeon, and other fishes, include those where fish have only been swum once and the metrics of swimming performance are assessed (e.g., time swum, speed achieved). Under natural conditions, there are ample instances where fish undergo multiple swimming cycles when traversing fish ways, culverts and other sources of fast water flow. While some evidence exists for salmonids, the effects of repeat swimming are not well known for sturgeon. The current study consisted of two experiments. The first examined the UCrit of juvenile shortnose sturgeon following three consecutive swimming trials with a 30 min recovery period between subsequent tests. The second examined the endurance swimming capacities of juvenile shortnose sturgeon following three consecutive swimming trials with a 60 min recovery period between subsequent tests. Our findings indicate that (i) UCrit was consistent (~2 body lengths/s) among swimming trials; (ii) significant individual variation exists between individuals in the endurance swimming trials; and (iii) consistent results exist for individuals across swimming trials in both the UCrit and the endurance swimming tests. These results suggest that juvenile shortnose sturgeon have a high recovery capacity, and their behaviour and morphology likely reflect aspects of their swimming capacities.     

Effect of body roll amplitude and arm rotation speed on propulsion of arm amputee swimmers

Only a limited amount of research has gone into evaluating the contribution made by the upper arm to the propulsion of elite swimmers with an amputation at elbow level. With assistance of computational fluid dynamics (CFD) modelling, the swimming technique of competitive arm amputee swimmers can be assessed through numerical simulations which test the effect of various parameters on the effectiveness of the swimming propulsion.This numerical study investigates the effect of body roll amplitude and of upper arm rotation speed on the propulsion of an arm amputee swimmer, at different mean swimming speeds. Various test cases are simulated resulting in a thorough analysis of the complex body/fluid interaction with a detailed quantitative assessment of the effect of the variation of each parameter on the arm propulsion. It is found that a body roll movement with an amplitude of 45° enhances greatly the propulsive contribution from the upper arm with an increase of about 70% in the propulsive force compared to the no roll condition. An increase in the angular velocity of the upper arm also leads to a concomitant increase in the propulsive forces produced by the arm.Such results have direct implications for competitive arm amputee front crawl swimmers and for those who coach them. One important message that emerges in this present work is that there exists, for any given swimming speed, a minimum angular velocity at which the upper arm must be rotated to generate effective propulsion. Below this velocity, the upper arm will experience a net resistive drag force which adversely affects swimming performance.     

Liver-derived endocrine IGF-I is not critical for activation of skeletal muscle protein synthesis following oral feeding

Background

Like humans, fish can be classified according to their athletic performance. Sustained exercise training of fish can improve growth and physical capacity, and recent results have documented improved disease resistance in exercised Atlantic salmon. In this study we investigated the effects of inherent swimming performance and exercise training on disease resistance in Atlantic salmon. Atlantic salmon were first classified as either poor or good according to their swimming performance in a screening test and then exercise trained for 10 weeks using one of two constant-velocity or two interval-velocity training regimes for comparison against control trained fish (low speed continuously). Disease resistance was assessed by a viral disease challenge test (infectious pancreatic necrosis) and gene expression analyses of the host response in selected organs.

Results

An inherently good swimming performance was associated with improved disease resistance, as good swimmers showed significantly better survival compared to poor swimmers in the viral challenge test. Differences in mortalities between poor and good swimmers were correlated with cardiac mRNA expression of virus responsive genes reflecting the infection status. Although not significant, fish trained at constant-velocity showed a trend towards higher survival than fish trained at either short or long intervals. Finally, only constant training at high intensity had a significant positive effect on fish growth compared to control trained fish.

Conclusions

This is the first evidence suggesting that inherent swimming performance is associated with disease resistance in fish.     

Measuring Ucrit and endurance: equipment choice influences estimates of fish swimming performance

This study compared the critical swimming speed (U_crit) and endurance performance of three Australian freshwater fish species in different swim‐test apparatus. Estimates of U_crit measured in a large recirculating flume were greater for all species compared with estimates from a smaller model of the same recirculating flume. Large differences were also observed for estimates of endurance swimming performance between these recirculating flumes and a free‐surface swim tunnel. Differences in estimates of performance may be attributable to variation in flow conditions within different types of swim chambers. Variation in estimates of swimming performance between different types of flumes complicates the application of laboratory‐based measures to the design of fish passage infrastructure.     

On-line Optimization of Biomimetic Undulatory Swimming by an Experiment-based Approach

An experiment-based approach is proposed to improve the performance of biomimetic undulatory locomotion through on-line optimization. The approach is implemented through two steps： （1） the generation of coordinated swimming gaits by artificial Central Pattern Generators （CPGs）; （2） an on-line searching of optimal parameter sets for the CPG model using Genetic Algorithm （GA）. The effectiveness of the approach is demonstrated in the optimization of swimming speed and energy effi- ciency for a biomimetic fin propulsor. To evaluate how well the input energy is converted into the kinetic energy of the pro- pulsor, an energy-efficiency index is presented and utilized as a feedback to regulate the on-line searching with a closed-loop swimming control. Experiments were conducted on propulsor prototypes with different fin segments and the optimal swimming patterns were found separately. Comparisons of results show that the optimal curvature of undulatory propulsor, which might have different shapes depending on the actual prototype design and control scheme. It is also found that the propulsor with six fin segments, is preferable because of hizher speed and lower energy efficiency.     

Effects of two parasites, Schistocephalus solidus (Cestoda) and Bunodera spp. (Trematoda), on the escape fast-start performance of three-spined sticklebacks

The fast‐start performance of three‐spined sticklebacks Gasterosteus aculeatus infected with Schistocephalus solidus and Bunodera spp. was determined and two distinct fast‐start responses (A and B) were observed. ‘A’ starts were of higher flexibility than B and three‐way ANOVA showed significant effects of A and B starts (P < 0·05), time (P < 0·05) and per cent standard body length, L_S (P < 0·05) on the orientation angle (angle of an individual segment of the fish with respect to the direction of travel). Schistocephalus solidus infection reduced maximum velocity (P < 0·05) and maximum acceleration (P < 0·05) of infected fish. Uninfected fish and fish infected with S. solidus up to a parasite index (parasite mass divided by the sum of fish and parasite mass) of 0·1 executed both types. Infected fish exclusively executed B starts for parasite index between 0·1 and 0·2. This was not due to a reduction in body flexibility associated with mechanical obstruction caused by S. solidus as no significant difference in the ratios of body width (P > 0·05) or depth (P > 0·05) to L_S were found between uninfected and infected fish. At a parasite index >0·2, infected fish were unable to perform escape fast‐starts increasing the likelihood of predation by their definitive hosts such as loons or belted kingfishers. Three‐spined sticklebacks infected with S. solidus with a parasite index of c. 0·2–0·3, however, were compromised by a suite of behavioural (e.g. increased foraging activity and amount of food consumed, increased risk associated with feeding and increased response latency to predatory stimuli), physiological (e.g. increased rate of oxygen consumption, slower growth, delayed sexual maturation and breeding success) and biomechanical (e.g. decreased fast‐start performance) factors. Bunodera spp. did not affect the escape fast‐start performance of three‐spined sticklebacks and no significant difference for maximum velocity (P > 0·05) and maximum acceleration (P > 0·05) was found.     

A gravity-induced regulation of swimming speed in Euglena gracilis

We investigated the autotrophic flagellate Euglena gracilis for gravity-induced modulation of the speed of swimming as previously documented for larger protozoan cells. Methods of video-tracking of swimming and sedimenting cells under 1 g and hypergravity up to 2 g, and computer-assisted data processing were applied. The vertical and horizontal swimming speed, and sedimentation rates of immobilized cells, were found to be linear functions of acceleration. Accounting for sedimentation in the observed upward and downward movements of Euglena, the active component of speed (propulsion) rose in proportion to acceleration. No saturation of gravikinesis was seen within the g-range tested. Gravity-dependent augmentation of speed was maximal in upward swimmers and decreased continuously over horizontal to downward swimmers. Linear extrapolations of the data to zero-g conditions suggest the absence of a threshold of gravikinesis in Euglena. Energetic considerations indicate a high sensitivity of gravitransduction near the level of Brownian molecular motion. Accepted: 22 August 1999     

Red muscle function in stiff-bodied swimmers: there and almost back again

Fishes with internalized and endothermic red muscles (i.e. tunas and lamnid sharks) are known for a stiff-bodied form of undulatory swimming, based on unique muscle-tendon architecture that limits lateral undulation to the tail region even though the red muscle is shifted anteriorly. A strong convergence between lamnid sharks and tunas in these features suggests that thunniform swimming might be evolutionarily tied to this specialization of red muscle, but recent observations on the common thresher shark (Alopias vulpinus) do not support this view. Here, we review the fundamental features of the locomotor systems in lamnids and tunas, and present data on in vivo muscle function and swimming mechanics in thresher sharks. These results suggest that the presence of endothermic and internalized red muscles alone in a fish does not predict or constrain the swimming mode to be thunniform and, indeed, that the benefits of this type of muscle may vary greatly as a consequence of body size.     

Altered burst swimming in rainbow trout Oncorhynchus mykiss exposed to natural and synthetic oestrogens

Juvenile rainbow trout Oncorhynchus mykiss were exposed to two concentrations each of 17β‐oestradiol (E2; natural oestrogen hormone) or 17α‐ethinyl oestradiol (EE2; a potent synthetic oestrogen hormone) to evaluate their potential effects on burst‐swimming performance. In each of six successive burst‐swimming assays, burst‐swimming speed (U_burst) was lower in fish exposed to 0·5 and 1 µg l^?1 E2 and EE2 for four days compared with control fish. A practice swim (2 days prior to exposure initiation) in control fish elevated initial U_burst values, but this training effect was not evident in the 1 µg l^?1 EE2‐exposed fish. Several potential oestrogen‐mediated mechanisms for U_burst reductions were investigated, including effects on metabolic products, osmoregulation and blood oxygen‐carrying capacity. Prior to burst‐swimming trials, fish exposed to E2 and EE2 for 4 days had significantly reduced erythrocyte numbers and lower plasma glucose concentrations. After six repeated burst‐swimming trials, plasma glucose, lactate and creatinine concentrations were not significantly different among treatment groups; however, plasma Cl^? concentrations were significantly reduced in E2‐ and EE2‐treated fish. In summary, E2 and EE2 exposure altered oxygen‐carrying capacity ([erythrocytes]) and an osmoregulatory‐related variable ([Cl^?]), effects that may underlie reductions in burst‐swimming speed, which will have implications for fish performance in the wild.     

How small puffers (Teleostei: Tetraodontidae) swim

 The tetraodontiform swimming mode has recently attracted attention because puffers swim very steadily and, unlike most of the other median and paired fin (MPF) swimmers, use more than one pair of fins to propel themselves through the water. To date, only one study presenting data concerning the swimming kinematics of puffers has been published, and this study dealt only with two species of large body size. In the present study, the swimming kinematics of small puffers (<6 cm TL) Tetraodon schoutedeni is described and compared to the swimming kinematics of larger puffers and boxfish. The results show that, generally, the swimming kinematics of small puffers is similar to that of larger puffers. The main differences that were found are in the synchronization of dorsal and anal fin motion, and in the motion of the pectoral fins, which complete their adduction before the dorsal and anal fins do. Maximum fin beat frequency was 18.4 Hz, much faster than that of larger puffers. At slow and median swimming speeds, dorsal fin beat amplitude increases with swimming speed and then remains constant between median and fast swimming speeds. The results confirm previous findings that puffers swim extremely steadily. Most of the differences in swimming kinematics between large and small puffers can be attributed to the size differences, but the difference in fin synchronization should be further studied to be completely understood. Received: September 27, 2002 / Revised: January 7, 2003 / Accepted: February 6, 2003     

Selective advantages conferred by the high performance physiology of tunas,billfishes, and dolphin fish

Tunas are extensively distributed throughout world's oceans and grow and reproduce fast enough to support one of the world's largest commercial fisheries. Yet they are apex predators living in the energy depauperate pelagic environment. It is often presumed that tunas evolved their specialized anatomy, physiology, and biochemistry to be capable of (a) high maximum swimming speeds, (b) high sustained swimming speeds, and/or (c) very efficient swimming, all of which help account for their wide distribution and reproductive success. However, a growing body of data on the energetics and physiological abilities of tunas do not support these assumptions. The three things demonstratively “high performance” about tunas, and probably other pelagic species such as marlin (Makaira spp. and Tetrapturus spp.) and dolphin fish (Coryphaena spp.), are (a) rates of somatic and gonadal growth, (b) rates of digestion, (c) rates of recovery from exhaustive exercise (i.e., clearance of muscle lactate and the concomitant acid load). All of these are energy consuming processes requiring rates of oxygen and substrate delivery above those needed by the swimming muscles for sustained propulsion and for other routine metabolic activities. I hypothesize that the ability of high performance pelagic species (tunas, billfishes, and dolphin fish) to deliver oxygen and metabolic substrates to the tissues at high rates evolved to permit rapid somatic and gonadal growth, rapid digestion, and rapid recovery from exhaustive exercise (abilities central to success in the pelagic environment), not exceptionally high sustained swimming speeds.     

Digestive capacities,inbreeding and growth capacities in juvenile Arctic charr Salvelinus alpinus

Genetic variation in growth performance was estimated in 26 families from two commercial strains of Arctic charr Salvelinus alpinus. Physiological determinants of growth and metabolic capacities were also assessed through enzymatic assays. A relatedness coefficient was attributed to each family using parental genotypes at seven microsatellite loci. After 15 months of growth, faster growing families had significantly lower relatedness coefficients than slower growing families, suggesting their value as indicators of growth potential. Individual fish that exhibited higher trypsin activity also displayed higher growth rate, suggesting that superior protein digestion capacities can be highly advantageous at early stages. Capacities to use amino acids as expressed by glutamate dehydrogenase (GDH) activities were lower in the liver of fast‐growing fish (13–20%), whereas white muscle of fast‐growing fish showed higher activities than that of slow‐growing fish for amino acid metabolism and aerobic capacity [22–32% increase for citrate synthase (CS), aspartate aminotransferase (AAT) and GDH]. The generally higher glycolytic capacities (PK and LDH) in white muscle of fast‐growing fish indicated higher burst swimming capacities and hence better access to food.     

The role of mechanical resonance in the neural control of swimming in fishes

The bodies of many fishes are flexible, elastic structures; if you bend them, they spring back. Therefore, they should have a resonant frequency: a bending frequency at which the output amplitude is maximized for a particular input. Previous groups have hypothesized that swimming at this resonant frequency could maximize efficiency, and that a neural circuit called the central pattern generator might be able to entrain to a mechanical resonance. However, fishes swim in water, which may potentially damp out many resonant effects. Additionally, their bodies are elongated, which means that bending can occur in complicated ways along the length of the body. We review previous studies of the mechanical properties of fish bodies, and then present new data that demonstrate complex bending properties of elongated fish bodies. Resonant peaks in amplitude exist, but there may be many of them depending on the body wavelength. Additionally, they may not correspond to the maximum swimming speed. Next, we describe experiments using a closed-loop preparation of the lamprey, in which a preparation of the spinal cord is linked to a real-time simulation of the muscle and body properties, allowing us to examine resonance entrainment as we vary the simulated resonant frequency. We find that resonance entrainment does occur, but is rare. Gain had a significant, though weak, effect, and a nonlinear muscle model produced resonance entrainment more often than a linear filter. We speculate that resonance may not be a critical effect for efficient swimming in elongate, anguilliform swimmers, though it may be more important for stiffer carangiform and thunniform fishes.