S125Abstracts / Comparative Biochemistry and Physiology, Part A 146 (2007) S107–S127

A6.58Is the Japanese skeleton shrimp Caprella mutica a filter

feeder? I. Head morphology and kinematics

K. Michel, S. Nauwelaerts, E. Stamhuis, (RuG, The Nether-lands); K. Boos, (SAMS, United Kingdom)

An active filter feeding organism strains suspended matter fromthe surrounding water using a sieving structure. Small marinefilter feeders however, have to cope with the physical problemsof the high viscosity as indicated by the low Reynolds number.In a highly viscous regime, organisms' appendages aresurrounded by a thick boundary layer, which makes movementand filter feeding difficult. In this study, we test whether Ca-prella mutica, a small marine amphipod frequently described asa filter feeder, is indeed capable of filter feeding by using itsantennae as sieves. This small crustacean feeds by swaying itsbody through the water. The forward movement of the headdrags along its two pairs of antennae of which the second pairof antennae possesses two rows of long setae. Juvenile C.mutica, being up to five times smaller then the adults, need tomove their appendages faster to reach a similar criticalReynolds number to make the antennae act like sieves. Inaddition, in adult C. mutica the first two pereonites areelongated, which may influence their filtering movements.Detailed head morphology was studied under a light micro-scope, while the filtering movements of both juvenile and adultC. mutica were recorded using a digital high-speed videocamera. The resulting kinematics of antennae, head and bodysegments showed that the antennae of both juvenile and adultC. mutica indeed move through the water at a Reynoldsnumber around three. Alternative methods of gathering food incaprellid amphipods will be discussed.

doi:10.1016/j.cbpa.2007.01.232

A6.59A new M.Sc. course in biomechanics at Manchester

R. Ennos, B. Sellers, J. Codd, (University of Manchester,United Kingdom)

Biomechanics is a central area of biology that enables scientiststo understand the mechanical design of organisms, but it is alsoincreasingly important as it underpins many of the appliedtechnologies such as biomaterials, tissue engineering andsports science. Unfortunately, progress in biomechanicsresearch has always been limited by the difficulty in attractingresearch students with the right expertise. Few universities runundergraduate courses in biomechanics, while masters' coursesin this area tend to be specialised and applications-led. Theaim of the new course at Manchester is to provide trulyinterdisciplinary training in comparative biomechanics, bring-ing students from both biological and physical sciencesbackgrounds to the level at which they undertake research atthe cutting edge. The course will have a strong practical

component, giving students extensive hands-on experience inbiomechanics right across the discipline, including both pureand applied biomechanics.

doi:10.1016/j.cbpa.2007.01.233

A6.60Kinematics of fast start swimming in a pelagic fish, the

mackerel Scomber scombrus

C. Lefrancois, (CRELA, France, IAMC, Italy); M. Cannas,(IMC, Italy, RELA, France); P. Morniere, (Aquarium LaRochelle, France); P. Domenici, (IAMC, Italy)

Scombrids are characterized by a relatively narrow streamlinedand stiff body, a lunate tail and a thin caudal peduncle. Sincesuch body characteristics participate to drag reduction,scombrids are recognized to be specialized cruisers, suited forpelagic environment. However these features contrast withadaptations for acceleration (such as a deep and flexible bodyand a large tail). The stiff body of scombrids also limits largeamplitude propulsive movements, as well as maneuverability,that are employed during some unsteady swimming behaviourssuch as fast starts. We investigated the escape response ofmackerel (length 34.2±2.9 cm), as an example of scombrids.Experiments were carried out in large circular tank (diameter4 m) filled with recirculated and filtered seawater set at atemperature of 18.3±0.5 °C. Escape responses were elicited bytriggering the fall of a small cylindrical object. Each individualwas startled 3 consecutive times with a minimum of 30 min ofrecovery between successive stimulations. A high speed camera(250 frames s−1) was used to record the escape responses.Locomotor variables, such as cumulative distance, speed andacceleration, were analysed, as well as turning rate and turningradius as indicators of the fish maneuverability. The perfor-mance that was found in mackerel will be discussed in relationwith their locomotor style (i.e. body/caudal fin periodicpropulsion), as well as their habitat.

doi:10.1016/j.cbpa.2007.01.234

A6.61Measuring muscle power and modeling hydrodynamicpower during anuran swimming

C. Richards, A. Biewener, (Harvard University, United States)

During swimming, anuran feet generate hydrodynamic thrustboth by translating backwards and rotating. Proximal musclestranslate the foot by extending the hip and knee joints whereasthe plantaris muscle extends the ankle, causing foot rotation.Previously, we recorded in vivo plantaris cycle power varyingover a range between 2.32 to 74.17 W/kgmuscle. However, sincethe ankle only rotates the foot, the plantaris' contribution tohydrodynamic power is unclear. This study explores how the

S126 Abstracts / Comparative Biochemistry and Physiology, Part A 146 (2007) S107–S127

relative roles of the ankle and proximal joints depend on theratio between foot translational velocity and rotational velocity(advance ratio, “AR”). We hypothesize that the ankle has tworoles in swimming: (1) To produce hydrodynamic power byrotating the foot and (2) to control the orientation of the foot,thus transmitting power from proximal muscles as the foottranslates. We expect that the ankle shifts between these twofunctions as AR changes from one swimming stroke to the next.Using a blade element approach, we modeled both thehydrodynamic forces on the foot as well as the ankle momentrequired to produce this fluid force. Preliminary findings showthat, for a given hydrodynamic power output, ankle power ismaximum at low AR. As AR increases, ankle power decreases,reaching a minimum of 28% maximum ankle power. Theseresults suggest that plantaris muscle power contribute sig-nificantly to hydrodynamic power both by rotating the foot andby controlling its orientation to the surrounding flow.

doi:10.1016/j.cbpa.2007.01.235

A6.62Aerodynamics of the bird wing: Flow patterns surroundingrotating bird-like wings

L. Flynn, E. Stamhuis, J. Videler, (University of Groningen,The Netherlands)

Force production in bird wing flapping may be related to bothconventional attached flow as well as development of leadingedge vortices. The shape of the bird wing emphasizes thedifferent uses for different sections of the wing: The arm wingis shaped like a conventional airfoil, with a round leading edgeand substantial thickness. The hand wing is thin with a sharpleading edge, much analogous to the shape of insect wingswhich have shown to use strong LEVs during flapping. Duringflapping flight, a bird wing faces an air flow composed oftranslational as well as rotational motion. The translationalcomponent is closely related to gliding without wing flapping,with the flow being steady and attached. The rotationalcomponent is more closely related to hovering. To get a clearerpicture of the relative function of the two wing sections andtheir aerodynamic features we strive to study them separatelyas well as in unison.To study the rotational component, we developed a rotarysystem for flow visualization and force measurement on birdwing models. With this system, we have tested the effects ofdifferent local effective and geometric angles of attack andvelocity profiles on development of stable LEVs on therevolving wing. These data are compared to LEV developmentfor water tunnel flapping and gliding models to show thedifferences between LEV structures and conditions for sheddingin each of the modes of movement.

doi:10.1016/j.cbpa.2007.01.236

A6.63Is the Japanese skeleton shrimp Caprella mutica a filter

feeder? II. Mechanics

S. Nauwelaerts, K. Michel, E. Stamhuis, (RUG, The Nether-lands); K. Boos, (SAMS, United Kingdom)

During filter feeding, a feeding current is passed through afiltration structure to separate food particles from the medium.Filter feeding at low Reynolds number poses specific problems.A Reynolds number represents the ratio of inertial to viscousforces. At low Reynolds number, any disturbance in the flowtends to be damped out by viscous shear. Water flow aroundsmall animals therefore tends to be laminar. This means that theboundary layer around the animal's appendages is relativelythick. A study of the kinematics of filter feeding in Caprellamutica, a small marine amphipod, showed that the appendageswork at a low Reynolds number indeed (Re ∼3 based on thedistance between two antennal setae), similar to what has beenfound for acorn barnacles. To understand the mechanicsinvolved in filter feeding at such a Reynolds number, wevisualized and quantified the flow patterns generated by aswaying C. mutica using Particle Image Velocimetry. At thestart of a swaying cycle, the water surrounding the animal isstanding still. This makes it difficult to accelerate it. The animalfirst moves slightly backwards, dragging along the surroundingmass of water and then quickly reversing the direction ofmovement and sweeps through the mass of water that wasmoving towards it. Local Reynolds numbers, leakiness andfiltration capacity of the setae on the second pair of antennaewill be discussed.

doi:10.1016/j.cbpa.2007.01.237

A6.64Onboard video in free-flight analysis of birds; use of headand eyes in vision-based flight control

Y. Ozawa, G. Taylor, (The University of Oxford, UnitedKingdom)

Birds of prey are highly dependent on vision for flight.However, previous studies of vision in birds have beenprincipally laboratory-based, using restrained birds and focus-ing on physiological scope. Here we consider the natural use ofhead movements in free-flight, utilising onboard video camerasmounted face-forwards on a Steppe Eagle Aquila nipalensis tocollect footage from which we derive quantitative data. Birdsexhibit only limited eye movements within the orbit, hencegaze shifts are achieved largely with movements of the head.Characteristically, fast saccadic gaze changes are alternatedwith periods of gaze fixation. This is known as nystagmus, andconfers two clear functional benefits: maximisation of steadyvision, and minimisation of unwanted visual input. Frame-by-frame analysis from several flights over four days confirmed