TEMPERATURE EFFECTS ON HAEMOLYMPH ACID-BASE STATUS IN VIVO AND IN VITRO IN THE TWO-STRIPED

• Main Authors: Grasshopper Melanoplus Bivittatus, M. Harrison
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1988
• Subjects: 1977; Heisler; 1984; Glass et al. 1985). This effect has been attributed to the; Carbonic acid
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.523.7483; http://jeb.biologists.org/content/140/1/421.full.pdf

In this study, I examine the effect of temperature on haemolymph acid-base status in vivo and in vitro in the two-striped grasshopper Melanoplus bivittatus. Melanoplus bivittatus experience wide (up to 40 °C) diurnal body temperature fluctuations in the field, but maintain body temperature relatively constant during sunny days by behavioural thermoregulation. Haemolymph pH was statistically constant (7-12) between 10 and 25°C, but decreased by-0017 units "CT1 from 25 to 40 °C. Relative alkalinity and fractional protein dissociation were conserved only at body temperatures at which feeding and locomotory activity occur, above 20°C. Haemolymph total CO2 (Ctot) increased from 10 to 20°C and decreased from 20 to 40°C. Haemolymph Pco2 increased from 10 to 20°C and was statistically constant between 20 and 40°C. Carbonic acid pKapp in haemolymph was 6-122 at 35°C, and decreased with temperature by —0-0081 units"C"1. Haemolymph buffer value averaged — SSmequivF'pHunit"1. Haemolymph pH changes with tem-perature were small (less than —0-004 units°C~1) in vitro at constant Pco2-Therefore, passive physicochemical effects cannot account for the pattern of acid-base regulation in vivo. The temperature shift from 10 to 20°C was accompanied by a net addition of 4-2-6-2 mmol I"1 of bicarbonate equivalents to the haemolymph. The temperature shift from 20 to 40°C was accompanied by a net removal of 10-14 mmol I"1 of bicarbonate equivalents from the haemolymph. Haemolymph acid-base regulation in vivo during temperature changes is domi-nated by active variation of bicarbonate equivalents rather than by changes in Pco2 as observed for most other air-breathers.