BEGIN:VCALENDAR VERSION:2.0 PRODID:-//wp-events-plugin.com//7.2.3.1//EN TZID:Europe/Paris X-WR-TIMEZONE:Europe/Paris BEGIN:VEVENT UID:5851@i2m.univ-amu.fr DTSTART;TZID=Europe/Paris:20221201T160000 DTEND;TZID=Europe/Paris:20221201T170000 DTSTAMP:20241120T200234Z URL:https://www.i2m.univ-amu.fr/evenements/the-effect-of-body-size-and-tem perature-on-flight-metabolic-rate-and-wing-kinematics-in-bees/ SUMMARY:Jon Harrison / Meghan Duell / Jordan Glass (Arizona State Universit y\, Tempe\, USA): The effect of body size and temperature on flight metabo lic rate and wing kinematics in bees DESCRIPTION:Jon Harrison / Meghan Duell / Jordan Glass: Body size and tempe rature are two dominant variables affecting animal flight performance and energetics\, yet many basic questions remain about patterns and causes.\nA mong flying birds and larger insects (and runners)\, mechanical power outp ut and energetic expenditure appear to show similar patterns with body mas s\, with power output scaling approximately isometrically (proportional to mass1)\, and metabolic rates scaling hypometrically (proportional to mass <\;1). This pattern may be due to lower frequencies of movement in large r species\, and resultant lower costs of calcium cycling\, as well as poss ibly improved elastic energy storage. However\, in small insects\, differe nt patterns are observed. Stingless bees (Meliponini) are a speciose tribe of tropical and subtropical bees that vary in body mass from 1 mg to >\ ; 100 mg\, and therefore provide an excellent model group for examining th e scaling of flight kinematics and energetics across this relatively unexp lored size range. My former Ph.D. student\, Meghan Duell\, spent multiple years in Panama studying the hovering flight of this group\, with a bit of help from me. Body size has strong effects on body temperatures achieved during flight\, with larger bees (over 50 mg) having flight muscle tempera tures 10-13°C above air temperature\, while thorax temperatures of smalle r bees are 1-2°C above air temperature. Thorax mass scaled isometrically\ , but larger species have relatively smaller and narrower forewings (scali ng slope of 0.5\, significantly less than the isometric prediction of 0.67 ). In contrast to the hypometric scaling of flight metabolic rates shown f or larger bees and birds\, within these stingless bee species\, flight met abolic rate scales strongly hypermetrically\, with a scaling exponent of 2 .25. This hypermetric scaling of flight metabolism cannot be explained by temperature differences among the species\, as applying a Q10 correction o f 2 only reduces the scaling slope to 2.1. In contrast to larger insects a nd birds\, wing beat frequency is independent of mass\, averaging 170 Hz. Regardless of body size\, stingless bees voluntarily lifted and flew with nectar loads nearly equal to their body mass. Combining our data across al l insects that have been measured to date\, it appears that flight metabol ic rate scales hypermetrically (scaling slope = 1.2) for insects less than 58 mg in body mass\, and hypometrically (slope = 0.67) for larger insects . The causes of this biphasic pattern remain unknown\, but the energetic b enefits to small size may arise from reduced lift requirements at lower Re ynolds numbers\, relatively larger wings\, and decreased wing venation.\nA n important question for understanding the effects of climatic warming on agriculture and biodiversity is how warming temperatures will affect the f light of insect pollinators. In stingless bees\, both field body temperatu res and the critical temperature that stops flight increases with body siz e. For smaller species\, heat wave temperatures (up to 40°C) already exce ed those at which bees can fly\, suggesting that for these tropical specie s\, with CTmax values ranging from 33 – 44°C\, further climatic warming could strongly inhibit flight and foraging. Honey bees (Apis mellifera) a re the most important agricultural pollinator\, and are particularly well- adapted for heat\, having a CTmax value of approximately 48°C. But\, how does variation in air and body temperature affect flight metabolic rate an d performance? Jordan Glass\, a current Ph.D. student in my lab has recent ly used variable gas mixtures to create a “flight treadmill” and to va ry body temperatures (heliox is more thermally conductive than nitrogen). At 35°C air temperature\, thoracic temperature is little-affected by heli ox\, and flight metabolic rate increases about 1.4x until failure at a gas density below about 0.4 (relative to normal air density of about 1.3 kg m -3). However\, at 23°C air temperature\, thorax temperature and flight me tabolic rate falls strongly as the fraction of heliox increases\, and bees failed to hover at gas densities below 0.7\, likely due to their inabilit y to sustain flight muscle temperatures sufficient generate high power out put. Honey bees show a classic thermal performance curve for maximal fligh t metabolic rate\, with an optimal flight muscle temperature of 39°C\, an d an increase of about 2% per 1°C below the optimal temperature\, and a d ecrease of about 5% per 1°C above the optimal. Nectar loading up to 60% o f body mass increases thorax temperatures 2-4°C and flight metabolic rate s by about 30% at air temperatures of 20°C and 30°C\, but did not affect either parameter at an air temperature of 40°C\, at which thorax tempera tures are about 45°C. Bees prevent further overheating during flight at 4 0°C air temperatures by dramatically increasing water loss rates. The fin ding that bees can carry similar heavy loads at flight muscle temperatures of 45°C with 30% less cost suggests an as yet unidentified mechanism (Jo rdan is still analyzing the high speed videos) to increase efficiency. Sup ported partially by USDA 2022-67013-36285.\nIOSSB Seminar ATTACH;FMTTYPE=image/jpeg:https://www.i2m.univ-amu.fr/wp-content/uploads/2 022/11/Jon_Harrison.png CATEGORIES:Interdisciplinary online seminar series on Biolocomotion LOCATION:Virtual event\, visioconférence\, virtual\, France X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=visioconférence\, virtual\ , France;X-APPLE-RADIUS=100;X-TITLE=Virtual event:geo:0,0 END:VEVENT BEGIN:VTIMEZONE TZID:Europe/Paris X-LIC-LOCATION:Europe/Paris BEGIN:STANDARD DTSTART:20221030T020000 TZOFFSETFROM:+0200 TZOFFSETTO:+0100 TZNAME:CET END:STANDARD END:VTIMEZONE END:VCALENDAR