Effect of leg kick on active drag in front-crawl swimming: Comparison of whole stroke and arms-only stroke during front-crawl and the streamlined position

The purpose of this study was to examine the effect of leg kick on the resistance force in front-crawl swimming. The active drag in front-crawl swimming with and without leg motion was evaluated using measured values of residual thrust (MRT method) and compared with the passive drag of the streamlined position (SP) for the same swimmers. Seven male competitive swimmers participated in this study, and the testing was conducted in a swimming flume. Each swimmer performed front-crawl under two conditions: using arms and legs (whole stroke: WS) and using arms only (arms-only stroke: AS). Active drag and passive drag were measured at swimming velocities of 1.1 and 1.3 m s⁻¹ using load cells connected to the swimmer via wires. We calculated a drag coefficient to compare the resistances of the WS, AS and SP at each velocity. For both the WS and AS at both swimming velocities, active drag coefficient was found to be about 1.6–1.9 times larger than that in passive conditions. In contrast, although leg movement did not cause a difference in drag coefficient for front-crawl swimming, there was a large effect size (d = 1.43) at 1.3 m s⁻¹. Therefore, although upper and lower limb movements increase resistance compared to the passive condition, the effect of leg kick on drag may depend on swimming velocity.     

Two new species of Laophontodes (Copepoda, Harpacticoida, Ancorabolidae) from McMurdo Sound, Antarctica

Two new species of harpacticoid copepods of the family Ancorabolidae are described from a subtidal site in Cape Armitage, McMurdo Sound, Antarctica. Laophontodes macclintocki sp. n. and L. spongiosus sp. n. are easily distinguished from the remaining members of the genus Laophontodes by the setal formula of swimming legs P2–P4.     

An analysis of swimming behavior in the portunid crab Callinectes sapidus

The swimming behavior of a portunid crab was analysed using high‐speed cinematography. The posture adopted for sideways swimming includes the rigid extension of trailing legs 1–4 and the cyclic beating of the modified 5th‐legs. There is also beating of leading legs 2–4. The 5th‐legs beat in near synchrony at approx. 4/sec while legs 2–4 beat in a normal walking gait at approx. 2/sec. There is no significant phase coupling between legs 2–4 and the 5th legs. Amputation of single walking‐legs (2–4) causes the remaining 2 legs to beat alternately and phase relationships now appear between remaining walking‐legs and the 5th‐legs. Amputation of single 5th‐legs cause no changes in walking‐legs and bilateral amputation effects are also absent. These results lead to the postulation of neural control systems to account for the observed behavior.     

Upstroke Thrust, Drag Effects, and Stroke-glide Cycles in Wing-propelled Swimming by Birds

A number of bird species swim underwater by wing propulsion.Both among and within species, thrust generated during the recoveryphase (upstroke) varies from almost none to more than duringthe power phase (downstroke). More uneven thrust and unsteadyspeed may increase swimming costs because of greater inertialwork to accelerate the body fuselage (head and trunk), especiallywhen buoyant resistance is high during descent. I investigatedthese effects by varying relative fuselage speed during upstrokevs. downstroke in a model for wing-propelled murres which descendat relatively constant mean speed. As buoyant resistance declinedwith depth, the model varied stroke frequency and glide durationto maintain constant mean descent speed, stroke duration, andwork per stroke. When mean fuselage speed during the upstrokewas only 18% of that during the downstroke, stroke frequencywas constant with no gliding, so that power output was unchangedthroughout descent. When mean upstroke speed of the fuselagewas raised to 40% and 73% of mean downstroke speed, stroke frequencydeclined and gliding increased, so that power output decreasedrapidly with increasing depth. Greater inertial work with moreunequal fuselage speeds was a minor contributor to differencesin swimming costs. Instead, lower speeds during upstrokes requiredhigher speeds during downstrokes to maintain the same mean speed,resulting in nonlinear increases in drag at greater fuselagespeeds during the power phase. When fuselage speed was relativelyhigher during upstrokes, lower net drag at the same mean speedincreased the ability to glide between strokes, thereby decreasingthe cost of swimming.     

Ants swimming in pitcher plants: kinematics of aquatic and terrestrial locomotion in Camponotus schmitzi

Camponotus schmitzi ants live in symbiosis with the Bornean pitcher plant Nepenthes bicalcarata. Unique among ants, the workers regularly dive and swim in the pitcher's digestive fluid to forage for food. High-speed motion analysis revealed that C.?schmitzi ants swim at the surface with all legs submerged, with an alternating tripod pattern. Compared to running, swimming involves lower stepping frequencies and larger phase delays within the legs of each tripod. Swimming ants move front and middle legs faster and keep them more extended during the power stroke than during the return stroke. Thrust estimates calculated from three-dimensional leg kinematics using a blade-element approach confirmed that forward propulsion is mainly achieved by the front and middle legs. The hind legs move much less, suggesting that they mainly serve for steering. Experiments with tethered C.?schmitzi ants showed that characteristic swimming movements can be triggered by submersion in water. This reaction was absent in another Camponotus species investigated. Our study demonstrates how insects can use the same locomotory system and similar gait patterns for moving on land and in water. We discuss insect adaptations for aquatic/amphibious lifestyles and the special adaptations of C.?schmitzi to living on an insect-trapping pitcher plant.     

Colopha hispanica sp.n. (Homoptera: Aphidoidea: Pemphigidae): an unusual endophytic aphid living inside the stems of Scirpus holoschoenus (Cyperaceae)

Abstract. A new aphid species of the genus Colopha (Pemphigidae: Eriosomatinae), Colopha hispanica is described from Spain. The apterae differ from those of other species of Colopha in the shortness of their antennae and legs, in the greater number of their wax glands and in the underdevelopment of the setal socket on the forelegs. These aphids live inside the stems of Scirpus holoschoenus (Cyperaceae); this is the first record of a truly endophytic aphid. The adults are immobile. C. hispanica is compared with the other known species of Colopha , with Kaltenbachiella pallida , a similar species also found in Spain and with Gharesia polunini , a primitive species of Eriosomatinae. The distribution and host plants of Colopha species are reviewed and discussed.     

Experimental Studies and Dynamics Modeling Analysis of the Swimming and Diving of Whirligig Beetles (Coleoptera: Gyrinidae)

Whirligig beetles (Coleoptera, Gyrinidae) can fly through the air, swiftly swim on the surface of water, and quickly dive across the air-water interface. The propulsive efficiency of the species is believed to be one of the highest measured for a thrust generating apparatus within the animal kingdom. The goals of this research were to understand the distinctive biological mechanisms that allow the beetles to swim and dive, while searching for potential bio-inspired robotics applications. Through static and dynamic measurements obtained using a combination of microscopy and high-speed imaging, parameters associated with the morphology and beating kinematics of the whirligig beetle''s legs in swimming and diving were obtained. Using data obtained from these experiments, dynamics models of both swimming and diving were developed. Through analysis of simulations conducted using these models it was possible to determine several key principles associated with the swimming and diving processes. First, we determined that curved swimming trajectories were more energy efficient than linear trajectories, which explains why they are more often observed in nature. Second, we concluded that the hind legs were able to propel the beetle farther than the middle legs, and also that the hind legs were able to generate a larger angular velocity than the middle legs. However, analysis of circular swimming trajectories showed that the middle legs were important in maintaining stable trajectories, and thus were necessary for steering. Finally, we discovered that in order for the beetle to transition from swimming to diving, the legs must change the plane in which they beat, which provides the force required to alter the tilt angle of the body necessary to break the surface tension of water. We have further examined how the principles learned from this study may be applied to the design of bio-inspired swimming/diving robots.     

Coordination between the legs and tail during digging and swimming in sand crabs

Rhythmic leg movements and tailflipping are mutually exclusive behaviours in most decapod crustaceans, but sand crabs (Anomura: Hippoidea) combine leg movements with simultaneous tailflipping or uropod beating for both digging and swimming. We examined the coordination between the legs and tail (abdomen and tailfan) of Blepharipoda occidentalis, Lepidopa californica (Albuneidae), and Emerita analoga (Hippidae). When either albuneid swims, the tail cycles at a higher frequency than the legs, and the two rhythms are not coupled. When albuneids begin digging, the tail's frequency drops to that of the legs, and its rhythm becomes phase coupled to the legs. In E. analoga the legs seldom move during swimming by uropod beating. During digging the frequency of the uropods and fourth legs starts at about double that of the second and third legs, but drops to that of the second and third legs as digging progresses. The fourth legs in E. analoga are coupled with the uropods; their outward movement (= power stroke) is concurrent with the uropod return stroke. The familial differences in leg coordination and in the coordination of the legs and tail account for the smooth descent of E. analoga beneath sand compared to the stepwise descent of the albuneids. Accepted: 23 August 1996     

Methods for the study of amphipod swimming: behavior,morphology, and fluid dynamics

A thorough hydrodynamic approach to the study of swimming in amphipods demands a multipronged attack. A possible first step would be to gather swimming behavior data and determine the biomechanics and kinematics of pleopod beat. This requires careful observation of the swimming modes, swimming speeds, body positions and other aspects of behavior and limb motion that are crucial to swimming. Secondly, it is important to describe the morphology of the body and swimming appendages. Detailed drawings of body shape and design, skeletomusculature, condylic structure, and setal density and distribution on the pleopods and pereopods, are the tools required to ascribe hydrodynamic function to specific limb and body morphology. Finally, the information gathered from behavioral observations bolstered by functional morphology studies is applied to fluid dynamic calculations of drag, lift, and thrust. The theoretical calculations are then compared with empirical determinations of drag, wake generation, vortex shedding frequency, and flow patterns around an amphipod. The fluid dynamic facet of this research is the most challenging and requires an excellent grasp of the fundamental concepts of fluid flow and access to some highly technical equipment. The proposed tripartite approach for the study of amphipod swimming is by no means an exhaustive review of all the techniques that can be employed to quantify amphipod swimming. It will nevertheless permit a rigorous and systematic study of amphipod swimming.     

Two new species of harpacticoid copepod from the South Orkney Islands, Antarctica, and a redescription of Idyellopsis typica Lang (Tisbidae)

Two new species of harpacticoid copepod belonging to the families Ameiridae and Ancorabolidae are fully described and illustrated. Pseudameria signyensis sp. nov. is very similar to P. crassicomis Sars but is distinguished from it by the presence of an extra seta on the inner border of the terminal segment of the endopodite of the fourth swimming leg. Laophontodes macropodia sp. nov. is distinguishable from all other species in the genus by the setal formula of the first four swimming legs but more particularly by the unique shape of the fifth leg. Idyellopsis typica Lang is by far the most abundant harpacticoid inhabiting sublittoral fine sand in Borg Bay, Signy Island, Antarctica. The female of this species is redescribed and the male described and illustrated for the first time.     

Leg coordination and swimming in an ant, Camponotus americanus

ABSTRACT. Leg movements of Camponotus americanus workers during straight swimming and turning are described herein. Thrust is generated through the different speeds and drag control between power v. return strokes in the forelegs. During the power stroke, femur, tibia and tarsus are straightened and thereby increase resistance; they bend backward during the return stroke. These thrusting legs move in a vertical plane which is similar to their position during walking. The backward stretching mesothoracic and metathoracic legs act, in conjunction with the gaster, as a rudder. Swimming in ants can be derived from walking; the major transformation being a suppression of the rhythmic movements of the middle and hind legs.     

Foreflipper propulsion in the California sea lion, Zalophus californianus

The family Otariidae comprises the only group of marine mammals that habitually use their pectoral appendages to generate propulsive forces during swimming. This method of propulsion was examined in the California sea lion ( Zalophus californianus ), a representative member of the family. High-speed films were taken as a sea lion swam against a water current generated inside a large flow channel. Thrust production was determined by examining the body's movement at various stages of the propulsive cycle. Sea lions generate thrust continuously throughout the stroke. Over its initial three-quarters, foreflippers act as hydrofoils creating forward thrust and lift as they move vertically through the water. Thrust production is greatest, however, near the end of the stroke, when flippers are used as paddles and are oriented broad side to the oncoming flow. The force generated by this three-phased system of propulsion is likely to be greater than that attainable by either an exclusively lift-based hydrofoil or drag-based paddling style of swimming.
The kinematic changes that enable sea lions to change speed were also investigated. Film records revealed that stroke amplitude became greater with speed, although total stroke duration remained essentially constant. Sea lions increase stroke frequency with velocity but large variations in the measured values suggest that changes in amplitude and flipper angle of attack are also important parameters for modulating swimming speed.     

Three-dimensional analysis of finlet kinematics in the chub mackerel (Scomber japonicus)

Finlets, which are small non-retractable fins located on the body margins between the second dorsal and anal fins and the caudal fin of scombrid fishes, have been hypothesized to improve swimming performance. The kinematics of three posterior finlets of the chub mackerel, Scomber japonicus, were examined using three-dimensional measurement techniques to test hypotheses on finlet rigidity and function during steady swimming. Finlet bending and finlet planar orientation to the xz, yz, and xy planes were measured during steady swimming at 1.2 lengths s(-1) in a flow tank. Despite very similar morphology among the individual finlets, there was considerable variability in finlet flexure during a stroke. Several of the finlets were relatively rigid and flat (with intrafinlet angles close to 180 degrees during the stroke), although intrafinlet angle of the proximal portion of the most posterior finlet varied considerably over the stroke and was as low as 140 degrees midstroke. Finlets showed complex orientations in three-dimensional space over a stroke, and these orientations differed among the finlets. For example, during tail deceleration the proximal portion of the fifth finlet achieves a mean angle of approximately 75 degrees with the xz plane, while the distal portion of this finlet is oriented at 110 degrees. Our data suggest that the trajectory of local water flow varies among finlets and that the most posterior finlet is oriented to redirect flow into the developing tail vortex, which may increase thrust produced by the tail of swimming mackerel.     

Toward Fast and Efficient Mobility in Aquatic Environment: A Robot with Compliant Swimming Appendages Inspired by a Water Beetle

Water beetles are proficient drag-powered swimmers,with oar-like legs.Inspired by this mechamsm,here we propose a miniature robot,with mobility provided by a pair of legs with swimming appendages.The robot has optimized linkage structure to maximize the stroke angle,which is actuated by a single DC motor with a series of gears and a spring.A simplified swimming appendage model is proposed to calculate the deflection due to the applied drag force,and is compared with simulated data using COMSOL Multiphysics.Also,the swimming appendages are optimized by considering their locations on the legs using two fitness functions,and six different configurations are selected.We investigate the performance of the robot with various types of appendage using a high-speed camera,and motion capture cameras.The robot with the proposed configuration exhibits fast and efficient movement compared with other robots.In addition,the locomotion of the robot is analyzed by considering its dynamics,and compared with that of a water boatman (Corixidae).     

Effect of propelling surface size on the mechanics and energetics of front crawl swimming

In swimming the propulsive force is generated by giving a velocity change to masses of water. In this process energy is transferred from the swimmer to the water, which cannot be used to propel the swimmer. Theoretical considerations indicated that an increase of the propelling surface size should lead to a reduced loss of energy to the water. Thus, in this study, the effect of artificially enlarging the propelling surface of the hand was examined. The effect was examined in terms of the propelling efficiency during front crawl swimming using the arms alone. The legs were floated with a small buoy as previously described (Toussaint et al., J. appl. Physiol. 65, 2506-2512, 1988a). In ten competitive swimmers (six male, four female) the rate of energy expenditure (power input, Pi), power output (Po), work per stroke cycle (As), distance per stroke cycle (d), work per unit distance (Ad), and propelling efficiency (ep) were determined at various swimming speeds once with and once swimming without paddles. At the same average velocity the effect of swimming with paddles was to reduce Pi, Po, and Ad by 6, 7.6, and 7.5% respectively, but to increase ep and As by 7.8 and 7%. The increase in distance per stroke cycle and the decrease in stroke cycle frequency matched the predicted values based on the theoretical considerations in which the actual increase in propelling surface size was taken into account.     

Scaling of ctenes and consequences for swimming performance in the ctenophore Pleurobrachia bachei

Ctenophores coordinate large macrociliary structures called ctenes to propel themselves through the water. The morphology and kinematics of the ctenes mediate swimming performance. We investigated morphological and kinematic factors affecting swimming performance in free‐swimming ctenophores (Pleurobrachia bachei) using high speed videography. Our morphological results showed that the relationship between body size and ctene morphology and arrangement in P. bachei were well described using linear (i.e., isometric) relationships, which suggests functional limitations of ctenes that vary among individuals of different sizes. Our kinematic results showed that isometric constraints on swimming performance can potentially be overcome by alterations in kinematics: (a) swimming speed in P. bachei increased with ctene beat frequency over a range of body lengths, and (b) the separation of ctenes into clumps of cilia allowed the ctene to increase in width during the effective stroke and decrease in width during recovery. Separation increases the surface area of the ctene during the effective stroke, likely increasing the thrust produced. The finding that ctenes are not monoliths and instead are separated into clumps of cilia has not been previously described, and we subsequently observed this trait in three other ctenophore species: Euplokamis dunlapae, Bolinopsis infundibulum, and Beroe mitrata. Flexibility in function may be a necessary corollary to isometric development of the ctenes as propulsive structures.     

Postembryonic development in Diaphanosoma brachyurum (Lievin, 1848) (Crustacea: Ctenopoda: Sididae)

Postembryonic females and males Diaphanosoma brachyurum from Lake Glubokoe (Moscow) have 3–4 and 3 juvenile instars, respectively. Females and males of the first three postembryonic instars can be identified by the different number of setae and setal rudiments on the proximal and distal segments of the exopodite of the swimming antennae: 3 + 7; (i + 3) + 7; 4 + (i + 7), respectively (i = rudiment of seta). The subsequent instars have 4 + 8 long plumose setae on these segments, but the fourth instar has the proximal lateral seta of the distal exopod segment slightly shorter and thinner than the others. The antennules and copulatory appendages of males are instar-specific. Diaphanosomas show small increments in body length during the postembryonic molts. The largest increments (about 115 m) occur during the first or second molts. The allometric equation of Huxley (1924) was used for a comparison of the relative growth rate of different body parts. In the middle of summer, the head and swimming antennae with the body and the antennal exopodite with the antennal basipodite grow in isometry. At the same time, the branches of the swimming antennae and their setae show allometric growth: the exopodite and distal setae grow faster than the endopodite and the lateral setae, respectively.     

Non-linear development of the frequency of swimming movements during ontogeny in rats

The choice of swimming as locomotor behaviour was justified by the fact that it could be elicited from birth to adult age. We have recorded electromyographic activities during swimming movements, on flexor muscles in front legs and hind legs (Spinodeltoidus and Gluteus superficialis). The mean frequency of activity of each limb during swimming, for animals aged from 0 to 20 or 30 days was then computed. The results showed an increase in frequency between 0 and 20 days from 1 to 4 Hz. This increase was not linear, but composed of different successive phases. After a first period of increase between 0 and 6 days (slope 0.25), for the hind limbs and the fore-limbs, we noted a plateau between 6 and 12 days during which the frequency was stable. This plateau was followed by another increase in the frequency values between 12 and 16 days (slope 0.30), followed by another plateau that corresponded to the adult frequency.     

Coordination and neuromuscular control of rhythmic behaviors in the blue crab,Callinectes sapidus

The stereotypical courtship display (CD) behavior of the male blue crab, Callinectes sapidus, includes an unusual component: the rhythmic waving of the swimming appendages above the carapace. This behavior occurs in a unique context but it resembles two other rhythmic behaviors performed using the swimming legs: sideways swimming and backward swimming. As a first step to understanding the mechanisms that allow the expression of apparently different rhythmic motor patterns, we have examined these behaviors using slow motion video analysis and electromyography of the basal muscles of the swimming legs in freely behaving crabs. The results show that these behaviors are distinguished by four parameters: the frequency of leg waving, the phase relationship between the legs, the presence of a stationary pause in basal muscle activity combined with rotation of the distal leg during CD, and an extended range of motion of these legs during CD and backward swimming, relative to sideways swimming. EMG analysis revealed that during sideways swimming, the sequence of muscular activity between the two legs was different. In contrast, during CD and backward swimming the sequence of activity for these legs is identical.Abbreviations CD courtship display - EMGs electromyograms - CD AMP courtship display in crabs with amputated fifth legs - CD1 crabs that voluntarily used one leg to perform courtship display waving - CD 1–3 courtship waving in cycles 1–3 - CD MID courtship waving after cycles 1–3 - M-C meral-carpal joint     

External morphology of Xyleborus ferrugineus (Fabr.) (Coleoptera: Scolytidae). I. Head and prothorax of adult males and females

The overall body dimensions and external morphology of the head, head appendages, prothorax, and prothoracic legs of the adult haploid male and diploid female Xyleborus ferrugineus (Fabricius) were examined by scanning electron microscopy and light microscopy, and analyzed for variation. The female is significantly larger (1.26 X) than the male. The length/width ratio of both the pronotum and elytron, and the pronotum-length/elytron-length ratio are significantly different in the male and female. These findings indicate a distinct sexual dimorphism in general body form. There is significantly greater variability in pronotal length and width in the male than the female. There are sexual differences in setal patterns and setal size variabilities on the dorsal pronotum and the terminus of the antennae.