title: A novel technique for the precise measurement of CO2production rate in small aquatic organisms as validated on aeshnid dragonfly nymphs.
abstract: The present study describes and validates a novel yet simple system for simultaneousin vivomeasurements of rates of aquatic CO2production (ṀCO2) and oxygen consumption (ṀO2), thus allowing the calculation of respiratory exchange ratios (RER). Diffusion of CO2from the aquatic phase into a gas phase, across a hollow fibre membrane, enabled aquaticṀCO2measurements with a high-precision infrared gas CO2analyser.ṀO2was measured with aPO2optode using a stop-flow approach. Injections of known amounts of CO2into the apparatus yielded accurate and highly reproducible measurements of CO2content (R2=0.997,P<0.001). The viability ofin vivomeasurements was demonstrated on aquatic dragonfly nymphs (Aeshnidae; wet mass 2.17 mg-1.46 g,n=15) and the apparatus produced preciseṀCO2(R2=0.967,P<0.001) andṀO2(R2=0.957,P<0.001) measurements; average RER was 0.73±0.06. The described system is scalable, offering great potential for the study of a wide range of aquatic species, including fish.
authors.affiliation: Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4 harter@zoology.ubc.ca.
authors.forename: Till S
authors.identifier: 0000-0003-1712-1370
authors.initials: TS
authors.lastname: Harter
authors.affiliation: Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4.
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Brauner
authors.affiliation: Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4.
authors.forename: Philip G D
authors.initials: PG
authors.lastname: Matthews
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000502:physiology; D002245:Carbon Dioxide / Q000378:metabolism*; D004058:Diffusion; D004867:Equipment Design; D008567:Membranes, Artificial; D009758:Nymph / Q000502:physiology; D063191:Odonata / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D015046:Zoology / Q000295:instrumentation
chemical_list: D008567:Membranes, Artificial; D002245:Carbon Dioxide; D010100:Oxygen
keywords: Fish; Hypoxia; Insect; Respiratory quotient; Respirometer; Stop-flow; Validation