DAY-TO-DAY CHANGES IN THE CHOLINERGIC SYSTEM DURING THE 5TH INSTAR OFTHE UZI-INFESTED SILKWORM BOMBYX-MORI

Day-to-day changes in acetylcholine (ACh) and acetylcholinesterase (AC hE) and activity levels during infestation by the uzifly Exorista sorb illans were studied in the central nervous system (CNS), hemolymph and silkgland of the larvae of the silkworm Bombyx mori. ACh content and AChE activity showed a gradual increase in all these tissues in both e xperimental and control larvae. Higher content of ACh in experimental larvae is indicative of higher synthesis despite hydrolysis to overcom e the stress caused by the maggot. Higher content of ACh also probably contributes to early maturation of the silkgland and causes the larva e to spin cocoons earlier than the controls. Low activity of AChE in t he infested larvae was probably due to the elevation of ACh. The decli ne and absence of AChE activity in the silkgland and hemolymph during the later days of the 5th instar indicate disruption in the structural integrity of the tissues leading to a lowered synthesis vis-a-vis low ered of activity AChE. The changes in the levels of ACh content and AC hE activity are indicative of the increase in the active state of the silkworm larvae under parasitic infestation.