The effects of temperature on aspects of respiratory physiology of the semi-terrestrial crabs, Uca inversa (Hoffmann) and Metopograpsus messor (Forskål) from the Red Sea

Abstract

The effects of temperature on aspects of the respiratory physiology of two semi-terrestrial crabs, Uca inversa and Metopograpsus messor have been studied. When exposed to increasing temperatures in the laboratory both species show a pronounced increase in both the rate of oxygen consumption (Mo2) and in heart rate; Q10 values were approximately 2–3 over the temperature range 15–40°C for both Mo2 and heart rate. Temperature did not, however, affect the relationships between Mo2 and fresh body weight and between heart rate and fresh body weight. The haemocyanin of both species was found to have a high oxygen affinity (P50 = 6.4 and 12.4 Torr for U. inversa and M. messor, respectively, pH = 7.9, temperature = 30°C) and moderately high Bohr values (−1.07 and −0.96 for U. inversa and M. messor, respectively). An increase in temperature resulted in a significant decrease in the oxygen affinity of the haemocyanin of both species (ΔH = −51.7 and −57.4 kJ.mol−1 for U. inversa and M. messor, respectively). Changes in temperature did not have a significant effect on either the Bohr value or the cooperativity of the pigment.