Effect of 20-hydroxyecdysone on neurosecretory cell activity in femaleHyalomma dromedarii synganglion (Acari: Ixodidae)

Twentyμg of 20-hydroxyecdysone (20-he) were applied topically to nymphalHyalomma dromedarii Koch on the day of detachment. In emerging adult females, some neurosecretory cells (nsc) in certain synganglion centers exhibited changes in size and/or neurosecretory material (nsm) shape, distribution and/or quantity. These changes were compared with those normally occurring in untreated unfed, semifed virgin and mated, and engorged females. 20-he effects included (a) accelerating the changes induced by mating and/or feeding in certainnsc, (b) reducing, to various extents,nsc response to mating and feeding, and (c) inducing changes in somensc which do not normally exhibit any changes in untreated females. The results suggest that (a) most femalensc respond more or less similarly to indigenous 20-he, (b) 20-he may have a role as a positive feedback regulator fornsm synthesis and/or release by certainnsc, (c) the response to 20-he may be primarily a function ofnsc location in the synganglion, and/or (d)nsc considered to be of one type may actually belong to different cell types.