Search

The insect group which includes cicadas harbours intracellular bacterial symbionts (endocytobionts) which are passed on from generation to generation in the form of a symbiont ball inserted between the egg membrane and the rear pole of the egg cell. Bioluminiescence methods can be used to measure the oscillations in ATP, ADP and AMP levels in egg systems which have been separated into a host and a symbiont egg part (Euscelidius variegatus), and which are exposed to constant light at 26 degrees C, 70% relative humidity and 7,000 lux. Comparison of the energy charge curves of host and symbiont egg parts suggests an antagonistic relationship at high frequencies, and a synchronous relationship at low frequencies (length of period 23--27 h). These relationship can, however, only be reproduced as phase-shifted oscillation patterns. The most appearing interpretation of this data is that the oscillation pattern represent a basic circadian rhythm, and that the phase-shift is produced by an underlying endogenous yearly rhythm. This, however, indicates a regulative coupling between the energy metabolism of the host egg and that of the prokaryotic egg-symbiont. Regulated correlations in the energy charge were also observed between the mitochondria and the cytoplasms/nucleus system. It follows that endocytobiosis can serve as an experimental model for the biochemical analysis of eucyte systems.

The insect group which includes cicadas harbours intracellular bacterial symbionts which are passed on from generation to generation in the form of a 'symbiont ball' inserted between the egg membrane and the rear pole of the egg cell. Bioluminiscence methods can be used to measure the oscillations in ATP, ADP and AMP levels in egg systems which have been separated into a host and a symbiont part (Euscelidius variegatus, Euscelis incisus), and which are exposed to constant light or light-dark variations under otherwise constant conditions (26 degrees C, 70% relative humidity, 7000 lux). The energy charge can be calculated from the ATP, ADP and AMP concentrations. Comparisons of such curves suggest an 'antagonistic' relationship in the energy metabolism of the host and symbiont parts of the egg. The minima of oscilaltions in the host's energy metabolism generally occur at the same time as the maxima in the endocytobionts energy metabolism. Antagonistic correlations between the nucleus/cytoplasm and mitochondria/plastids were also observed in the eucyte system. Analogies between the two systems can be explained satisfactorily by the endosymbiont theory of the origin of eucytes. It follows that insect endocytobioses can serve as an experimental model for the biochemical analysis of the eucyte system.