Meeting Abstract

85.2  Sunday, Jan. 6  Temperature dependent variation in respiratory patterns and spiracular control in Rhodnius prolixus HEINRICH, EC*; BRADLEY, TJ; Univ. of California, Irvine; Univ. of California, Irvine eheinric@uci.edu

Our current understanding of insect respiratory control indicates that spiracular activity is regulated by two interacting feedback loops which monitor and respond to changes in internal pCO₂ and pO₂. Spiracles open when pCO₂ reaches a critically high threshold (2-6 kPa) or when pO₂ becomes critically low (4-5 kPa). Given that the spiracles open in response to a specific pCO₂, the volume of CO₂ released in a burst by a discontinuously respiring insect should remain constant independent of metabolic rate. However, previous studies which manipulated metabolic rate via temperature found that burst volume decreases at higher temperatures. We used Rhodnius prolixus to determine if this variation is caused by changes in metabolic rate or by an effect of temperature on spiracular control. We increased metabolic rate by either increasing ambient temperature or by feeding Rhodnius a bloodmeal. Burst volume decreased significantly as temperature increased from 18°C to 38°C (ANOVA, F=89.58, p<0.001) but showed no relationship to metabolic rate in fed animals measured at 24°C (BV= -0.0016MR + 0.0243, R2=0.0015). Burst duration and time between bursts decreased in both treatment groups. Additionally, insects that experienced temperature variation abandoned discontinuous respiration at lower metabolic rates than those in the fed treatment group. Our study suggests that the set point at which the spiracles open in response to CO₂ is dependent on ambient temperature. It is clear that the respiratory patterns produced by insects are influenced by both temperature and metabolic rate. These results provide a window for examining the mechanisms by which insects sense and respond to pCO₂ and pO₂. This work was supported by the NSF grant IOS-0920683 (TJB).