THE EFFECTS OF TEMPERATURE ON ASPECTS OF RESPIRATORY PHYSIOLOGY OF THE SEMITERRESTRIAL CRABS, UCA INVERSA (HOFFMANN) AND METOPOGRAPSUS MESSOR (FORSKAL) FROM THE RED-SEA

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 laborato ry both species show a pronounced increase in both the rate of oxygen consumption (Mo-2) and in heart rate; Q(10) values were approximately 2-3 over the temperature range 15-40 degrees C for both Mo-2 and heart rate. Temperature did not, however, affect the relationships between Mo-2 and fresh body weight and between heart rate and fresh body weigh t. The haemocyanin of both species was found to have a high oxygen aff inity (P-50 = 6.4 and 12.4 Torr for U. inversa and M. messor, respecti vely, pH = 7.9, temperature = 30 degrees C) and moderately high Bohr v alues (-1.07 and -0.96 for U. inversa and M. messor, respectively). An increase in temperature resulted in a significant decrease in the oxy gen affinity of the haemocyanin of both species (Delta H = -51.7 and - 57.4 kJ.mol(-1) for U. inversa and M. messor, respectively). Changes i n temperature did not have a significant effect on either the Bohr val ue or the cooperativity of the pigment.