DISCONTINUOUS CARBON DIOXIDE RELEASE IN THE EASTERN LUBBER GRASSHOPPER ROMALEA GUTTATA AND ITS EFFECT ON RESPIRATORY TRANSPIRATION

Abstract

Ventilatory patterns were examined in the Eastern lubber grasshopper Romalea guttata and correlated with respiratory transpiration. Discontinuous release of CO2 was only observed in quiescent individuals during their scotophase. Interburst periods (spiracles closed) alternated with bouts of CO2 emission and O2 consumption (burst phase); no true ‘flutter’ phase was observed. Cycle duration decreased with increasing temperature in both hydrated and dehydrated individuals. Metabolic rates for this large, sluggish species are lower than those reported for smaller and/or more active grasshoppers. Water loss rates fell within an expected range of values for arthropods from mesic environments. Respiratory transpiration accounted for only 1.9-3.9 % of the total water loss between 15 and 30 sC and for only 7 % of the water loss during the burst phase of the cycle. These data indicate that the cyclic release of CO2 in this adult insect does not result in substantial savings of water.