The development of the insect nervous system. I. An analysis of postembryonic growth in the terminal ganglion of Acheta domesticus
Gymer, A.; Edwards, J.S.
Journal of Morphology 123(2): 191-197
This study describes the post-embryonic growth of the terminal ganglion in Acheta domesticus in terms of volume and cell number. All measurements were made at the beginning of each instar from hatching until the final moult on animals reared under controlled conditions. The terminal ganglion increases about 40-fold in volume from 2 × 10'/.1,3 in the first instar to 85 × 10' A' in the adult. A double logarithmic plot of ganglion volume against body weight shows that the ganglion volume is a function of body weight to the 0.56 power. Initially the neuropile grows at a greater rate than the cortex; in later stages they increase at the same rate. Increase in cell number was determined from serial sections. The total number of cells, based on corrected nuclear counts, increases from 3,400 to 20,000. There is little or no increase in the number of neurons. There are approximately 2,000 association neurons and 100 motor neurons in all stages. The number of glial cells increases from 1,000 to 17,000. Their multiplication rate appears to be related to the increase in neuron volume. Despite the increase in glial cell number, increase in cell volume is primarily responsible for the increase in total volume of the ganglion.