ROLES OF NEUROSECRETORY-CELLS ON GROWTH AND REPRODUCTION AND THEIR SEASONAL-VARIATION IN ACHATITA-FULICA (GASTROPODA, ACHATINIDAE)

The injections of Achatina fulica with cerebral ganglion homogenate an d with optic tentacle homogenate revealed that both substances had No effect on body growth of A. fulica. However, the cerebral ganglion hom ogenate appeared to increase the oocyte production in the ovotestis of snails. Seasonal variation in number and size of neurosecretory cells in the cerebral ganglia of A. fulica was observed The number of neuro secretory cells in the cerebral ganglia was high during the rainy seas on (May-October, 1993) and low during the dry season (November-April, 1993). The highest number of neurosecretory cells and the largest cell size were observed in May. The number and size of collar cells in the optic tentacles were similar throughout the year.