Respiratory Function and Thermal Acclimation in Tropical Invertebrates

Abstract

IT has been reported¹ that some cold blooded animals show an increased respiratory quotient when exposed to high temperatures. We have investigated this phenomenon and other aspects of exposure to higher temperatures in connexion with thermal acclimation in molluscs and arthropods. Among the Mollusca we have used two species of Gastropoda common in the irrigation canals of the cotton growing country near Khartoum, both of them vectors of bilharzia; they are Biomphalaria pfeifferi (Dunker) and Bulanus truncatus (Audouin). Crustacea were represented by the terrestrial woodlice (Isopoda) Periscyphis jannonei Arcangeli and Metoponorthus pruinosus (Brandt), insects by the day-active desert beetle Adesmia antiqua Klug and by the night-active desert beetle Ocnera hispida Forskål, and arachnids by the scorpion Leiurus quinquestriatus (Hemprich and Ehrenberg), and by the camel spider (Solifugae) Galeodes grantae Pocock. In the latter two species juvenile animals were used; the others were adults. The snails and wood-lice were supplied with food at all times except when the measurements were being taken; the beetles and arachnids, which can survive more than 6 months' starvation in the laboratory, were unfed. Measurements were made on individual animals after acclimation first at 20° C and then at 34° C, each for 48 h, measurements being made at the same two temperatures by Warburg manometry. It was thus possible to compare the effects of acclimation with these two temperatures in measurements made on the same individuals.