S76 Abstracts / Comparative Biochemistry and Physiology, Part A 150 (2008) S74–S92

to characterise a complete family of protein isoforms and determinethe impact of changes in their expression on whole-animal function.

doi:10.1016/j.cbpa.2008.04.113

A3.7Do changes in muscle mechanics explain alterations in locomotorperformance caused by thermal acclimation in the saltwatercrocodile (Crocodylus porosus)?

R. James (Coventry University); F. Seebacher (University of Sydney,Australia)

Locomotor performance can be constrained by organismal capa-city to respond to environmental change, such that individuals mosteffective in compensating for environmental variability will gain aselective advantage. Locomotor performance is influenced by under-lying muscle mechanics which in turn depend on metabolic capacitiesand the muscle protein isoforms expressed. Temperature influenceslocomotor performance via acute effects on muscle mechanics andmetabolism. Additionally many ectotherms reversibly change theirmuscle protein and metabolic phenotypes in response to long-term(e.g. seasonal) changes in thermal environment. Locomotor performanceacclimates perfectly in the saltwater crocodile (Crocodylus porosus), suchthat sustained swimming speed in cold acclimated animals at 20 °Cmatches warm acclimated animals at 30 °C (Glanville and Seebacher,2006). Our aimwas to investigate thermalplasticity ofmuscle function ina thermoregulating ectotherm (Crocodylus porosus) to test the hypoth-eses that: a) muscle mechanics acclimate to different temperatures andcan explain changes in locomotor performance; b) changes in metaboliccapacitiesmayunderlie someof the alterations inmusclemechanics.Wetested mechanical properties of caudofemoralis muscle in crocodilesacclimated to winter (cold, mean Tb=20 °C) and summer (warm, meanTb=30 °C) conditions and related these findings to indices of metaboliccapacities. Muscle work loop power output increased with cold accli-mation at both test temperatures, as a result of shorter activation andrelaxation times.We conclude that by combining thermoregulationwithplasticity in muscle mechanics, crocodiles maximise performance inenvironments with highly variable thermal properties.

Reference

Glanville, E.J., Seebacher, F., 2006. JEB 209, 4869–4877.

doi:10.1016/j.cbpa.2008.04.114

A3.8Kinematics and muscle function during landing flight in thepigeon (Columba livia)

A. Berg, A. Biewener (Harvard University)

When landing on a perch, a bird must decelerate and reach a verylow velocity at the appropriate moment. To investigate deceleration inflapping flight, we studied landing flight in the pigeon (Columba livia,N=4) using high-speed video, EMG, and sonomicrometry. Prior tolanding, the birds' body angle increased dramatically, resulting in agreater frontal area, and thus an increase in drag. The body angleincrease corresponded to an increase in the stroke plane angle (rela-

tive to the horizontal), which shifted from being negative during levelflight to positive during landing. The positive stroke plane anglesuggests that the wings were forcing air forward. Therefore, pigeonslikely increase the rearward component of aerodynamic force in orderto decelerate prior to landing.

Until the final landing wingbeat, the pectoralis and biceps tendedto reach their shortest lengths simultaneously, reflecting the flexedwing posture observed at the end of downstroke. In the final wingbeatof landing, the pectoralis shortened less and the stroke amplitudecorrespondingly decreased. The biceps also shortened less in the finalwingbeat, and continued to shorten after the pectoralis began tolengthen. The biceps was active during lengthening and remainedactive until after it began to shorten. This activation pattern may allowthe production of high force at the elbow to accelerate the wing whenit reverses direction at the end of the downstroke.

doi:10.1016/j.cbpa.2008.04.115

A3.9A semi-empirical model of blowfly flight dynamics and controldeveloped using a VR simulator

R. Bomphrey, G. Taylor (Oxford University)

Here we present a semi-empirical model of the lateral flight dyna-mics of the blowfly Calliphora vicina. The data were collected using afully immersive Virtual Reality flight chamber for tethered insectscapable of providing stimuli in the visual, aerodynamic and inertialsensory modalities. Modified data-projectors allow for projection of 7bit greyscale images at N300 fps, with a mean resolution of 4.3 pixels/°over a spherical back-projection surface with diameter 1 m. Theapparatus simulates a range of steady flight conditions through apotentially unlimited set of moving visual environments, with theability to vary the subject's physical and visual orientation dynami-cally via a programmable motor system. These inputs are synchro-nised with 6-component force-moment recordings which are used toparameterize the flight dynamics model.

doi:10.1016/j.cbpa.2008.04.116

A3.10Flow control in the wings of a Steppe eagle Aquila nipalensis:Automatic aeroelastic devices

A. Carruthers, A. Thomas, G. Taylor (Oxford University)

Aeroelastic devices used by a Steppe Eagle Aquila nipalensis duringunsteady manoeuvres are analysed. Chaotic deflections of the upperw-ing coverts are observedusingvideo cameras carried by thebird (50 fps).The deflections indicate trailing-edge separation but attached flow nearthe leading-edge during flapping and gust response, and completelystalled flows upon landing. At high angle of attack the underwingcoverts deflect automatically along the leading-edge and high-speeddigital video (500 fps) is used to analyse these deflections in greaterdetail during shorter (30m) and longer (50+m) perching sequences. Thelonger perching sequences usually follow a stereotyped three-phasesequence comprising a glide, pitch-up manoeuvre (similar to an M-wing) and deep stall (reminiscent of a cross parachute). Deployment ofthe underwing coverts is closely phasedwithwing sweeping during thepitch-up manoeuvre, and is accompanied by alula protraction.

S77Abstracts / Comparative Biochemistry and Physiology, Part A 150 (2008) S74–S92

Surprisingly, the alula is passively peeled from its tips prior to activeprotraction. The shorter flights follow a stereotyped flapping perchingsequence, with deployment of the underwing coverts closely phasedwith alula protraction and the end of the downstroke. It is proposed thatthe underwing coverts operate as an automatic highlift device,analogous to a Kruger flap. We suggest that the alula operates as astrake, promoting formation of a leading-edge vortex on the swepthand-wing when the arm-wing is completely stalled, and hypothesisethat its active protraction is stimulated by its initial passive deflection.These aeroelastic devices appear to provide flow control duringunsteady manoeuvres, and may also provide sensory feedback.

doi:10.1016/j.cbpa.2008.04.117

A3.11Aerial jousting in orchid bees: Biomechanics versus behavior incompetitive interactions

S. Combes (Harvard University)

Many animals engage in competitive interactions to establish terri-tories, gain access to resources, and attract mates. Locomotion is oftencentral to these interactions, yet the relative importance of locomotoryperformance versus behavioral strategy is unknown. Male orchid beesperform aggressive aerial jousting matches over sources of aromaticoils, which the bees collect from plants and store in their hind legs,presumably to be used for courtship. These jousting matches caninclude extended aerial maneuvering bouts, chases, and aerialcollisions. We filmed wild, Panamanian orchid bees jousting overfragrance sources, and analyzed videos to determine the 3-dimen-sional movements of each bee during the interaction. We alsocategorized and recorded several distinct aggressive behaviors, anddetermined the proportion of time that bees spent engaged in variousactivities. We find that bees involved in aggressive interactions spendless time collecting fragrance, less time hovering, and more timeengaged in fast, maneuvering flight. The relative time spent on each ofthese activities, aswell asmean flight velocity, depends on the numberof bees involved. Traditional measures of flight performance such asvelocity and acceleration are not correlated with an individual bee'ssuccess (time spent on the fragrance source), although other bio-mechanical traits such as collision stability may play a role. Overallaggressiveness does appear to be related to success in these en-counters, but behavioral strategy varies depending on the number ofinteracting bees. These results highlight the importance of consideringbiomechanical performance in the context of complex locomotorybehaviors performed by wild animals.

doi:10.1016/j.cbpa.2008.04.118

A3.12Altitudinal variation in flight mechanics and energetics of thegiant Andean hummingbird

M. Fernandez (University of California Berkeley)

Hummingbirds are unique in their ability to sustain hovering, one ofthe most energetically demanding forms of locomotion. The giant hum-mingbird (Patagona gigas) weighs on average 20 g, twice as much as thesecond largest hummingbird, making it an outlier in the hummingbirdbody size distribution. Because power requirements increase with body

mass, whereas maximum aerobic capacity of flying animals scalesnegatively with body mass, large body size presents a double mechan-ical/metabolic challenge to hovering flight. P. gigas inhabits a broadaltitudinal range fromsea level to 4000m.At high elevations, the lower airdensity will reduce lift production and mechanical power output mustincrease to compensate. At the same time, the lower partial pressure ofoxygen may constrain metabolic power production. Thus, the occurrenceof P. gigas at a wide range of altitudes provides an excellent “naturalexperiment,” and the opportunity to assess biomechanical and energeticresponses of this bird to natural hypobaric differences. The objectives ofthis study are to measure aspects of flight from the mechanical to thephysiological, in sites separated by 3700 m in altitude. I will study how P.gigasmakes changes in its life style and foraging strategies at high altitude.Preliminary data suggest that at high elevationP. gigas increaseswing beatfrequency and stroke amplitude, as well as oxygen consumption duringhovering. This study will help us to understand the mechanical andphysiologicalmechanisms that have enabledP. gigas to adapt to extremelydifferent environmental conditions, despite his large size.

doi:10.1016/j.cbpa.2008.04.119

A3.13Wing motion and wake structure of bat flight

T. Hubel, K. Breuer, A. Song, S. Swartz (Brown University)

The goal of the project is to gain a detailed understanding of thewing motion and wake structure of Short-nosed fruit bats (Cynopterusbrachyotis) flying in a wind tunnel at a flight speeds ranging from3–6.5 m/s. Themeasurements give closer insights in the lift and thrustgeneration over the wing beat cycle and should confirm previousobservations in both wind tunnels and flight cages which suggestindividual preferences in changing different flight parameters such asflapping frequency, angle of attack or flapping amplitude in response tochanging flight speeds. It is expected that the particular flight para-meters differ from individual to individual but are consistent over therange of flight speed.

Detailed measurements of kinematics and high resolution wakestructure, perpendicular to the flow stream, are captured simulta-neously by using 3 high-speed cameras (Photron Fastcam 1024,resolution 1024×1024 pixels, 200 fps) coupled to time-resolvedparticle image velocimetry (PIV). The 200 Hz double-pulse Nd:YAGlaser (Litron LPY 703-200) enables the observation of the develop-ment of the circulation in the tip vortex in the observation plane foreachwing beat cycle. Each PIV acquisition sequences can be correlatedwith the respective kinematic history, gained by tracing the markerspainted on the joints and membrane of the wings.

doi:10.1016/j.cbpa.2008.04.120

A3.14A leading edge vortex slows down the descent of maple seeds

D. Lentink (Wageningen University); W. Dickson (California Instituteof Technology); J. van Leeuwen (Wageningen University); M.Dickson (California Institute of Technology)

In still airmaple seeds swirl straightdown to earth at a rate of roughly1 ms−1 and therefore rely, like other autorotating seeds, on wind to bedispersed. Dispersal is more effective when seeds descent slow enough