A new system for concurrent measurement of respiration and water loss in arthropods

Abstract

A new, flow-through system for the concurrent measurement of water loss and CO, production from arthropods is described. The system employs an Alz03 sensor to measure the moisture content of the air stream, and an infrared gas analyzer to determine the COz content. The system responds rapidly, is accurate, and provides a continuous record of both variables at constant or increasing temperatures. Preliminary studies on the house cricket, Achetu domesticus, showed that water loss and Vco2 were highly variable depending upon the activity of crickets and that water loss increased greatly as a result of oral and anal discharges of fluid. Occlusion of the mouth and anus (paraffin) reduced water loss and Vco2 at 30°C by 82 and 46%, respectively. Strong correlations between Vco2 and water loss were observed in crickets whose mouth and anus had been sealed, both in long-term (3 hour) isothermal studies and under conditions of rapidly increasing temperature. Key Kords arthropods, Acheta domesticus, carbon dioxide, metabolism, respiration, water loss Water loss and metabolic rate are frequently measured in insect physiology (see Edney, '77;Miller, '74). Most studies have employed gravimetric techniques to measure water loss and manometry to estimate metabolic rate. These techniques are suitable for long-term studies, but are limited (with some exceptions) in their ability to monitor acute changes in water loss and metabolic rate in response to activity or temperature fluctuations. Further, because it has proven very difficult to combine techniques that would permit the simultaneous measurement of water loss and metabolic rate in arthropods, the relationship between oxygen uptake and water loss has been based largely on correlations obtained from independent plots of these two processes (Ahearn, '70; Hadley, '70). This paper describes a new technique for the continuous and simultaneous measurement of water and COO production in arthropods. The system employs a high-resolution moisture sensor and an infrared gas analyzer to measure the amounts of water and COz released by the animal into a moving air stream. Preliminary results are presented showing the effects of various treatments and temperature on the rates and patterns of water loss and COZ production in the house cricket, Achetu dornesticus. MATERIALS AND METHODSThe system for measuring water loss and COZ production comprises two separate instruments operating in series: the transpiration monitor (TM) and an infrared COZ gas analyzer. The latter is a commercially available instrument which will be described in a later section. The TM is a custom instrument constructed by J. Stuart Enterprises (Grass Valley, CAI which employs an A1203 sensor to measure the moisture content of a moving air stream. Although the TM and its calibration procedure have been described in detail elsewhere (Hadley et al., '82) a brief summary of its features pertinent to this study will be reported here. Transpiration monitor (TM)Very pure bottled air (21.5% Oz, 78.5% Nz, no detectable CO...

Colony Breeding System Influences Cuticular Bacterial Load of Formosan Subterranean Termite (Isoptera: Rhinotermitidae) Workers

“…On return to the laboratory, the mouth and anus of 20 workers per sample were sealed with parafÞn (Quinlan and Hadley 2005) to prevent contamination of the surface by gut bacteria. Seals were checked under a dissecting scope by gently squeezing the termites with sterile forceps and observing if gut content was released.…”