Zur Rolle des Frontalganglions bei Larven der Schabe Periplaneta americana

Abstract

Removal of the frontal ganglion in starving larvae results in a considerable decrease in body weight. The animals die within 10 to 15 days at a relative humidity of about 55%, if they receive neither food nor water. On cutting the two frontal connectives, the animals lose less weight than after removal of the frontal ganglion but more than after a sham operation. Cutting only one of the frontal connectives and the recurrent nerve together with the connective nerve results in a decrease in body weight which is not different from the decrease after a sham operation. The decrease in body weight occurs more slowly and the animals survive longer the higher the relative humidity. The loss of weight in starving ganglionectomized animals at an r.h. of about 0% corresponds to the loss in dead animals under the same conditions. Oxygen consumption is unchanged after operation. The osmolarity in the haemolyph of ganglionectomized animals increases during the 3 days after operation by more than 25 per cent. When water is offered, the frontal ganglionectomized animals survive the operation much better. Daily feeding with a 40 per cent starch mixture is still more effective. On this ‘diet’ the body weight increases only a little. This also occurs with normal animals. When feeding with flaked oats, the operated animal's body weight increases as little as with a starchy diet, this is in contrast with unoperated animals. The post-operative date of ecdyis does not shift after frontal ganglionectomy. The operated animals have difficulties in shedding their old cuticle. Their abdomen is peculiarly shrunken and their size (width of the pronotum) scarcely increases. It is just the same after cutting both frontal connectives. The regeneration of the legs takes place in a normal manner after frontal ganglionectomy. This shows that protein synthesis cannot be blocked after the removal of the frontal ganglion. The results are discussed in the light of current ideas on the control of water balance in insects. It is concluded that the frontal ganglion does not produce a hormone. It conducts inhibitory nerve impulses coming from osmoreceptors to the neurosecretory centres in the pars intercerebralis, where a diuretic factor is produced. It is possible that the osmotic non-equilibrium between cuticle and blood cannot be maintained when the frontal ganglion is removed.