INTRACELLULAR CALCIUM TRANSIENTS IN SUCTORIAN PROTOZOA (TRICHOPHRYA SPP) - CORRELATION WITH SPONTANEOUS TENTACLE CONTRACTIONS

The luminescent photoprotein aequorin was used to measure intracellula r free Ca2+ in three species of suctorian protozoon, Trichophrya riede ri, Trichophrya collini end Trichophrya rotunda. Resting [Ca2+](i) ran ged from about 75-110 nM, and was unaffected by a change in temperatur e of the perfusate, Spontaneous Ca2+ transients were observed in all t hree species, with peak amplitudes ranging from 100-600 nM. In T. ried eri and T. rotunda, three categories of transient (small, intermediate , large) were recorded; T. collini displayed only small transients. In both T. riederi and T. collini, raising the temperature from 5 degree s to 26 degrees C led to an increase in the frequency of transients, F urthermore, in T. riederi, large transients occurred only at the highe r temperature, The frequency of spontaneous contractions of the tentac les of 7. riederi was also temperature-dependent. Increasing the tempe rature over the range 5-26 degrees C led to a concomitant increase in contraction frequency and a decrease in mean tentacle length, The poss ible mechanisms of spontaneous Ca2+ transient generation and their rol e in the control of contraction are discussed.