The Larval and Pupal Neurosecretory System of Calliphora Erythrocephala Meigen

Abstract

Neurosecretory cells are present in the pars intercerebralis and the sub-oesophageal ganglion of the larvae and pupae of Calliphora erythrocephala Meigen. On account of their topography these cells are subdivided into 6 groups in the brain and into 2 groups in the sub-oesophageal ganglion; the time of appearance and disappearance is discribed. A modification of the paraldehyd-fuchsine method was used to demonstrate neurosecretory cells. During larval and pupal development there are marked differences amongst the neurosecretory cell types concerning their staining-intensity and changes in this intensity throughout larval and pupal life. The average total number of neurosecretory cells in the hemispheres increases in the first instar from 2 to 8, in the second from 8 to 16, in the feeding period of the third instar from 16 to 20, in the resting period of that instar from 20 to 30 and at the beginning of pupation it decreases to 16 to 20. In the pupae the number of neurosecretory cells is constantly 18. The staining-intensity varies also and shows distinct maxima: in the first two instars 3 to 5 hours before moulting and in the resting period 15 to 20 hours before pupation is started. The axons of the neurosecretory cells transport the neurosecretory material via the nervi corporis cardiaci I and II to the corpus cardiacum. The amount of neurosecretory material in these axons and the corpus cardiacum fluctuates. They possess maxima in stainability at the same time as the cells. It is difficult to correlate these fluctuations with the activity of the neurosecretory system, but there are indications for the function of some cell types. There are indications for a higher activity of two types of neurosecretory cells at the moment the ecdyson production has been started, about 15 to 20 hours before the beginning of pupation. This observation is also made some hours before or at the time of the first and second moult. There are some indications that the neurosecretory cells of the sub-oesophageal ganglion are concerned with locomotor activity. After a strong desiccation it is obvious that the neurosecretory activity of the neurosecretory cells in the brain and sub-oesophageal ganglion has decreased considerably, except for one cell type. Distinct differences in acid phosphatase activity have been found between the neurosecretory cells of the brain.