Hissing Cockroaches May Save Water by Closing Their Spiracles.

We examined the effects of humidity on the metabolic rates and respiratory patterns of Gromphadorhina portentosa to determine whether insects transition from continuous, cyclical and discontinuous (DGC) respiration in response to water conservation. Eight male G.portentosa were placed under 5 different humidity treatments (0, 23, 40, 60, 80% RH). Using flow through respirometry we: 1) determined the effect of humidity on metabolic rate; 2) observed if changes in metabolic rate were correlated with changes in closed/flutter (CF) or the open (O) phase of DGC; and 3) determined whether increased spiracular closure was correlated with an increase in water retention. Although G. portentosa had similar rates of CO2 release when placed under 0, 40, 60 and 80% RH, cockroaches placed at 23% RH had a significantly higher metabolic rate. There was no effect of humidity on the duration of the CF phase of the DGC. However, the O phase of DGC was significantly longer when G. portentosa was placed at humidity levels above 23% RH. Interestingly we saw that the average rate of mass lost to the environment did not change when cockroaches were placed at humidity levels ranging from 0–80% RH. This suggests that modulation of the spiracles allows G. portentosa to regulate the amount of water lost to the environment.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.