Limb Beat Research Articles

New Insights into Sea Turtle Propulsion and Their Cost of Transport Point to a Potential New Generation of High-Efficient Underwater Drones for Ocean Exploration

Sea turtles gracefully navigate their marine environments by flapping their pectoral flippers in an elegant routine to produce the required hydrodynamic forces required for locomotion. The propulsion of sea turtles has been shown to occur for approximately 30% of the limb beat, with the remaining 70% employing a drag-reducing glide. However, it is unknown how the sea turtle manipulates the flow during the propulsive stage. Answering this research question is a complicated process, especially when conducting laboratory tests on endangered animals, and the animal may not even swim with its regular routine while in a captive state. In this work, we take advantage of our robotic sea turtle, internally known as Cornelia, to offer the first insights into the flow features during the sea turtle’s propulsion cycle consisting of the downstroke and the sweep stroke. Comparing the flow features to the animal’s swim speed, flipper angle of attack, power consumption, thrust and lift production, we hypothesise how each of the flow features influences the animal’s propulsive efforts and cost of transport (COT). Our findings show that the sea turtle can produce extremely low COT values that point to the effectiveness of the sea turtle propulsive technique. Based on our findings, we extract valuable data that can potentially lead to turtle-inspired elements for high-efficiency underwater drones for long-term underwater missions.

Sea Turtles Employ Drag-Reducing Techniques to Conserve Energy

Sea turtles are recognised as one of the ocean’s most remarkable migratory species, accomplishing journeys that cover thousands of kilometres. This fact is even more extraordinary when considering sea turtles consume mostly low-energy foods. The biology of sea turtles dominates the literature; however, the swimming strategies they employ to achieve their migratory success from a biomechanical and hydrodynamic viewpoint is relatively unexplored. In past research, the sea turtle’s upstroke has been debated among researchers as to whether it is passive or for thrust production. In this work, we recreate a model based on the green sea turtle (Chelonia mydas) and develop an ad hoc testing rig to uncover the secrets behind the sea turtle’s upstroke. Our findings suggest sea turtles utilise a passive upstroke that can substantially lower the animal’s drag coefficient to levels that cause insignificant losses in swim speed despite not developing any thrust force. This can conceivably save the animal a notable amount of energy as the upstroke is responsible for a large percentage of the overall limb beat cycle. These findings could potentially pave a path towards developing high-efficiency bioinspired underwater drone technologies.

Integrated Timing of Stroking, Breathing, and Kicking in Front-Crawl Swimming: A Novel Stroke-by-Stroke Approach Using Wearable Inertial Sensors.

Quantitative evaluation of synergic action among the different body segments is fundamental to swimming performance. The aim of the present study was to develop an easy-to-use tool for stroke-by-stroke evaluation of a swimmer’s integrated timing of stroking, kicking, and breathing. Twelve swimmers were evaluated during one trial of 100 m front-crawl swimming at self-selected speed. Five three-axial inertial sensors were mounted on the head, wrists, and ankles. Algorithms for the wrist entry into the water, the lower limb beat during the downward action, and the exit/entry of the face from/into the water were developed. Temporal events identified by video-based technique, using one sagittal moving camera, were assumed as the gold standard. The performance was evaluated in terms of the root-mean-square error, 90th percentile of absolute error, coefficient of variation, Bland–Altman plots, and correlation analysis. Results of all temporal events showed high agreement with the gold standard, confirmed by a root-mean-square error of less than 0.05 s for absolute temporal parameters and less than 0.7% for the percentages of the stroke cycle duration, and with correlation coefficients higher than 0.856. The protocol proposed was not only accurate and reliable, but also user-friendly and as unobtrusive as possible for the swimmer, allowing a stroke-by-stroke analysis during the training session.

A Tail's Tale: Biomechanical Roles of Dorsal Thoracic Spine of Barnacle Nauplii.

Many marine invertebrates have complex life histories that begin with a planktonic larval stage. Similar to other plankton, these larval invertebrates often possess protruding body extensions, but their function beyond predator deterrence is not well-documented. For example, the planktonic nauplii of crustaceans have spines. Using the epibiotic pedunculate barnacle Octolasmis spp., we investigated how the dorsal thoracic spine affects swimming and fluid disturbance by comparing nauplii with their spines partially removed against those with intact spines. Our motion analysis showed that amputated Octolasmis spp. swam slower, in jerkier trajectories, and were less efficient per stroke cycle than those with intact spines. Amputees showed alterations in limb beat pattern: larger beat amplitude, increased phase lag, and reduced contralateral symmetry. These changes might partially help increase propulsive force generation and streamline the flow, but were insufficient to restore full function. Particle image velocimetry further showed that amputees had a larger relative area of influence, implying elevated risk by rheotactic predator. Body extensions and their interactions with limb motion play important biomechanical roles in shaping larval performance, which likely influences the evolution of form.

A novel apparatus for evaluating contaminant effects on feeding activity and heart rate in Daphnia spp.

Cladoceran are animals of significant importance to freshwater bodies such that changes in their populations may result in drastic shifts in the food web. Numerous studies have investigated the effects of toxicants, and the effects of chemical and physical habitat changes to these animals. Most of these studies investigated more general endpoints such as mortality, reproduction, growth, and food consumption over time, and less frequently examined molecular endpoints such as enzyme activity or gene expression. However, behavioral and physiological endpoints that link the organism and molecular level endpoints are scarce. In this study, we designed an apparatus that allows for the simultaneous investigation of three essential behavioral and physiological endpoints in Daphnia, including ventilation, food uptake rate, and heart rate. Using our apparatus, we studied the effect of cadmium (Cd), suspended particles, and food on the beating rate of thoracic limbs and the frequency of mandible rolling in Daphnia magna. We also studied the effect of temperature on the heart and thoracic limb beat frequency. The results show that both Cd and suspended particles reduce the activity of mandibles and thoracic limbs. Thoracic limb movements and heart rate increased gradually with temperature. Our toxicity tests show that changes in feeding, ventilation, and heart rate are easily detected using this method.

ARE PLEOPODS JUST “MORE LEGS”? THE FUNCTIONAL MORPHOLOGY OF SWIMMING LIMBS IN EURYTHENES GRYLLUS (AMPHIPODA)

Abstract Amphipods, like most swimming crustaceans, employ a drag-based mechanism to produce thrust. The propulsors are paddle-shaped pleopods that move parallel to the direction of motion. These paired abdominal limbs generate both the propulsive thrust and the respiratory currents that bathe the thoracic gills. This study addresses the basic kinematics of motion and the pleopodal skeletomusculature of the deep-sea scavenger Eurythenes gryllus. The limb beat cycle consists of a power stroke where the three pleopod pairs, with their setal fan outstretched, swing sequentially through an arc parallel to the body axis, and then return anteriorly in a collapsed and bent configuration. The joint connecting the body to the muscular peduncle is complex, allowing promotion and remotion along the main body axis. Several hard plates for extrinsic muscle attachment are surrounded by arthrodial membrane. The extrinsic musculature is proportioned accordingly, with a large mass of muscles controlling the power stroke a...

Are Pleopods Just “More Legs”? The Functional Morphology of Swimming Limbs in Eurythenes Gryllus (Amphipoda)

Amphipods, like most swimming crustaceans, employ a drag-based mechanism to produce thrust. The propulsors are paddle-shaped pleopods that move parallel to the direction of motion. These paired abdominal limbs generate both the propulsive thrust and the respiratory currents that bathe the thoracic gills. This study addresses the basic kinematics of motion and the pleopodal skeletomusculature of the deep-sea scavenger Eurythenes gryllus. The limb beat cycle consists of a power stroke where the three pleopod pairs, with their setal fan outstretched, swing sequentially through an arc parallel to the body axis, and then return anteriorly in a collapsed and bent configuration. The joint connecting the body to the muscular peduncle is complex, allowing promotion and remotion along the main body axis. Several hard plates for extrinsic muscle attachment are surrounded by arthrodial membrane. The extrinsic musculature is proportioned accordingly, with a large mass of muscles controlling the power stroke and a few long muscles generating the recovery stroke forces. The intrinsic musculature within the peduncle and annular rami serves two functions: (1) many long, thin muscle fibers within the peduncle function as support muscles responsible for shape changes; (2) large, strap-like muscles control flexion for the recovery stroke and abduction-adduction of the exopod for the power stroke. Several ancillary skeletal structures enhance swimming efficiency: reinforcement in the pleonal wall for muscle attachment, coupling hooks between the pleopod pair to effectively create a single paddle, the complementary shapes of the exopod and endopod, and an exopodal hook that facilitates the complete collapse of the pleopods on the recovery stroke. The functional design of the pleopod maximizes efficient recovery stroke motion while still providing strong remotion during the recovery stroke.

How Daphnia cope with algae selected for inedibility in long- running microcosms

Macro video records of restrained feeding Daphnia enabled us to measure simultaneously carapace gape, claw rejection rate, filter limb beat rate, and mandible movement rate. We compared the effects of high and low concentrations of highly edible algae and of inedible algae, the latter selected by long-term Daphnia grazing in oligotrophic microcosms. Inedible algae slowed the filtering process and influenced the carapace gape (widening at low concentration and narrowing at high), but did not affect the rejection rate.

Swimming behaviour of developmental stages of the calanoid copepod Temora longicornis at different food concentrations

The swimming behaviour of developmental stages of the marine calanoid copepod Temora longicornis was studied using 2-dimensional observations under a microscope and a 3-dimensional filming technique to analyze swimming mode, swimming speed and swimming trajectories under different food concentrations. The nauplii swam intermittently in a stop-and-go fashion. The swimming behaviour of the smallest feeding stage (N2) did not change with different food concentrations. The largest nauplius stages reacted to an increased food concentration by increasing the percentage of time spent swimming. All copepodid stages swam continuously their mouthparts moving nearly 100% of the time. Copepodids can therefore only increase their feeding effort by increasing their limb beat frequency. Adult females showed low swimming speeds at very low food concentrations, higher swimming speeds at intermediate concentrations and low swimming speeds at very high food concentrations. This agreed with expectations based on the optimal foraging theory. Males behaved differently from the females. Not only was the average swimming speed of males higher at similar food conditions, but they also maintained a very high swimming speed at very high food concentrations. This increased swimming activity in the males may be linked to a mate seeking strategy. Neither males nor females showed any obvious differences in turning behaviour at different food concentrations.

Direct observation of toxic effects of cyanobacterial extracellular products on Daphnia

The filtrate from a suspension of the cyanobacterium Anabaena minutissima var. attenuata depressed thoracic limb beat frequency of Daphnia carinata by 38–45% in a food-free medium. Repeated exposure to the filtrate produced a similar depression of activity with full or neary full recovery. Response time to the filtrate was 5–8 min and recovery time was 8–12 min. The dose effect on limb beat frequency was continuous, linear, correlated with increased concentration and with no threshold. There was no relationship between body length and limb beat frequency.

Effects of temperature on tilt evoked swimming in the crabs Carcinus and Macropipus

1. 1.|Integrated muscle activity, total number of limb beats and the maximum instantaneous limb beat frequency were measured in crabs during a standardized tilt regime at a series of different water temperatures between 10 and 25°C. 2. 2.|Total integrated activity and total number of limb beats showed a general increase for a decrease in temperature in all groups. Frequency of limb beat was always higher for Macropipus depurator than for Carcinus maenas, with M. depurator showing an increase and C. maenas a decrease in frequencies at extreme temperatures. 3. 3.|The temperature of acclimation of C. maenas affected the response of the crab in all parameters studied while all the results can be related to the size and normal environmental temperature range of the two species studied.

Spectral analyses of movements made by the cephalic appendages of copepods

Movements of Calanus helgolandicus, Centropages typicus and Ternora longicornis cephalic appendages, which are involved in feeding and swimming, were investigated. When considered together, results of limb beat traces and of spectral and autocorrelation analyses show that the movements of copepods cephalic limbs are dependent upon the species, and are indicative of sensory feeding behaviour. T. longicornis exposed to mechanosensory stimulation, in the form of Sephadex beads, phytoplankton cells or natural particles, produced appendage-movement traces varying in beat frequency and amplitude. Particle size had the greatest influence on appendage movements. Chemical stimulation in the absence of particles (dissolved free amino acid cocktails) generally increased the appendage beat frequency, but did not cause fluctuations in beat amplitude such as occurred with particles. Analyses of the movements of the first maxillae indicate that for filter-feeding calanoid copepods, mechanoreception contributes to parbcle handhng, and chemoreception contributes both to an increase in the speed of the feeding current and the recognition of food. During feeding In copepods, it is likely that mechanoand chemoreception are complementary and act in conjunction.

Locomotion in hatchling leatherback turtles Dermochelys coriacea

Hatchling leatherback turtles can only swim forwards, and employ synchronized beating of the forelimbs whether swimming slowly or quickly. The hind limbs make no contribution to propulsion. Effectively, the hatchlings have two swimming speeds; subsurface and fast (30 cm s‐1) or surfaced and slow (8 cm s‐1). Intermediate velocities are transitory; the hatchlings were never seen to rest without movement, nor did they exhibit gliding of the type seen in green turtles. During fast (‘vigorous’) swimming, power is developed on both the upstroke and downstroke of the limb cycle. During slow swimming, power is only developed during the upstroke—a consequence of the orientation of the axis of limb beat which is opposite in direction to that of cheloniid sea turtles. Terrestrial locomotion is laboured and features an unstable gait which involves simultaneous movement of all four limbs and forward overbalancing during each limb cycle.

Changes in the limb beat movements of barnacle nauplii in the presence of food organisms

The limb beat movements of Balanus (= Semibalanus) balanoides (L.) and Elminius modestus Darwin nauplii were used to study the response of the larvae to patches of microalgae. Observations were made on restrained larvae in relatively large volumes of flowing sea water. The behaviour of the larvae was recorded on video-tape and analysed, frame-by-frame, after the experiment. It was found that the volume through which the antennae moved (= swept volume; a combination of antennal surface area, beat frequency, amplitude and percentage of time spent swimming) in a minute was increased, for both species, in the presence of microalgae. The response was evoked by Skeletonema costatum (Grev.) Cleve and Tetraselmis suecica (Kylin) Butcher at temperatures of 10–20°C. The swept volume rose with increasing algal concentration to a plateau, at concentrations above 100 cells·μl −1,≈50% higher than the values obtained without algae.

The effect of size and temperature on the frequency of limb beat of Temora longicornis Müller (Crustacea : Copepoda)

Copepods normally swim by rhythmically beating the cephalic limbs, so records of antennal movements represent their activity. The limb beat rate of Temora longicornis Müller was determined in relation to several factors. There was an inverse relationship between swimming rate and body size, and activity increased with environmental temperature up to 20–25°C. Copepods readily acclimated, as those kept at 15°C were less active than those kept at 5°C. The summer population was also less active in the low temperature range, but swimming reached a higher rate at higher temperatures than were tolerated by the winter population. No difference in rate of limb beat was found between similar sized males and females over a wide range of temperatures.

A study of feeding behaviour in Temora longicornis (Müller) (Crustacea:Copepoda)

The feeding behaviour of Temora longicornis (Müller) was studied using a suction restraint technique in large volumes of sea water. Observations and records were made with a video-tape recorder and Temora cephalic limb beat movements recorded with a micro-impedance pneumograph. The classical copepod feeding swirls, shown for other calanoid copepods, were shown to be artefacts of the constraints imposed by small volumes of sea water. No feeding swirls were seen when sea water flowed past the animals at a speed equivalent to that of slow swimming by copepods. Food particles were brought to the restraining surfaces of the cephalic appendages from in front, and not behind, the maxillipedes. Female T. longicornis were shown to increase their limb beat frequency and amplitude when presented with patches of the diatom Skeletonema. Such an increase in limb beat movement would suggest that Temora could adjust its feeding speed to the availability of algal food in the sea water.

Modellversuche zum Stoffhaushalt in Aquarien bei verschiedenem Salzgehalt : Kühl, H. and H. Mann, 1962 Kiel. Meeresforch., 18 (3) ( Sonderheft): 89–92

The limb beat movements of Balanus (= Semibalanus) balanoides (L.) and Elminius modestus Darwin nauplii were used to study the response of the larvae to patches of microalgae. Observations were made on restrained larvae in relatively large volumes of flowing sea water. The behaviour of the larvae was recorded on video-tape and analysed, frame-by-frame, after the experiment. It was found that the volume through which the antennae moved (= swept volume; a combination of antennal surface area, beat frequency, amplitude and percentage of time spent swimming) in a minute was increased, for both species, in the presence of microalgae. The response was evoked by Skeletonema costatum (Grev.) Cleve and Tetraselmis suecica (Kylin) Butcher at temperatures of 10–20°C. The swept volume rose with increasing algal concentration to a plateau, at concentrations above 100 cells·μl−1,≈50% higher than the values obtained without algae.

Contribution á l'étude du métabolisme de l'azote minéral au milieu marin. Microflore dénitrifiante de certaines zones littorales méditerranéennes : Lagarde, Edmond, 1962 Pubbl. Staz. Zool., N Napoli, 32 (Suppl.): 490–496

The limb beat movements of Balanus (= Semibalanus) balanoides (L.) and Elminius modestus Darwin nauplii were used to study the response of the larvae to patches of microalgae. Observations were made on restrained larvae in relatively large volumes of flowing sea water. The behaviour of the larvae was recorded on video-tape and analysed, frame-by-frame, after the experiment. It was found that the volume through which the antennae moved (= swept volume; a combination of antennal surface area, beat frequency, amplitude and percentage of time spent swimming) in a minute was increased, for both species, in the presence of microalgae. The response was evoked by Skeletonema costatum (Grev.) Cleve and Tetraselmis suecica (Kylin) Butcher at temperatures of 10–20°C. The swept volume rose with increasing algal concentration to a plateau, at concentrations above 100 cells·μl−1,≈50% higher than the values obtained without algae.