Sensitivity to allatostatins of corpora allata from larval and adult female Diploptera punctata

Abstract

Corpora allata from adult and larval Diploptera punctata females were tested for sensitivity to inhibition of juvenile hormone synthesis by allatostatins in vitro. Inhibition by allatostatin 1 was consistently high (60–82%) after larval and adult moults and thereafter changed with corpora allata activity. In 0–8-day virgin females, with relatively constant juvenile hormone synthesis, the sensitivity of the corpora allata remained relatively constant (51–71%). Mated females in both the first and second vitellogenic cycles showed similar changing patterns of inhibition: low inhibitions (35 and 50%) at the peaks of the two cycles of juvenile hormone synthesis and an increase to maxima (83 and 77%) as juvenile hormone synthesis declined. During the 60-day pregnancy between the two cycles, rates of juvenile hormone synthesis remained low, yet the sensitivity to allatostatin 1 declined gradually. This pattern of sensitivity of adult corpora allata was also observed with allatostatin 4. Sensitivity of corpora allata from 2-day virgins and first- and second-cycle females to allatostatin 1 showed a pronounced increase between 10 −9 and 10 −8 M for all ages tested except day 50 in which a marked increase in sensitivity occurred between 10 −8 and 10 −7 M. In penultimate-instar larvae the sensitivity of the glands to inhibition by allatostatin 1 decreased to 29% one day after the midstadium peak of juvenile hormone synthesis, and recovered only slightly as juvenile hormone synthesis subsequently decreased. In final-instar larvae also, the sensitivity of the corpora allata declined after the moult, but this occurred as juvenile hormone synthesis decreased. Inhibition remained low even as juvenile hormone synthesis began to increase at the end of the final stadium. Similar sensitivities to allatostatins 2, 3 and 4 were found for corpora allata from penultimate- and final-instar larvae.