M. Kruatrachue et al., GENERAL ANATOMY AND HISTOLOGY OF THE NERVOUS-SYSTEM IN ACHATINA-FULICA, Journal of the Science Society of Thailand, 19(1), 1993, pp. 1-24
The nervous system of Achatina fulica is composed of 13 ganglia : a pa
ir of buccal ganglia, a pair of cerebral ganglia, a pair of pleural ga
nglia, a pair of parietal ganglia, a pair of pedal ganglia, a pair of
tentacular ganglia and a single visceral ganglion. All ganglia give ri
se to many nerve branches which supply the snail body. They are surrou
nded by two layers of connective tissues: the thick outer layer and th
e thin inner layer connective tissue. Within the ganglia, there are ne
rve cells or ganglionic cells of four sizes: (1) the small cells which
have the diameter of < 20 microns, (2) the medium-sized cells which h
ave the diameter of 20 - 39 microns, (3) the large cells which have th
e diameter of 40 - 99 microns, and (4) the giant cells which have the
diameter of > 100 microns. In addition, there are masses of very small
cells or globuli cells which have the diameter of 5 - 7 microns in th
e cerebral ganglia and the tentacular ganglia. Furthermore, in the cer
ebral ganglia, there is a group of neurosecretory cells which are char
acterized by a round heterochromatic nucleus and 4 large vacuole. Simi
larly, neurosecretory cells or collar cells were found around the fing
er-like projections of tentacular ganglion. These cells contain small
round nuclei and their Cytoplasm is full of granules and droplets.