Fig. 1. Peptides known to reduce primary urine production [Tenmo-ADFa (ADFa), Tenmo-ADFb (ADFb) and Manse-CAP_2b (CAP_2b)] were tested at 1 µmol l^–1 for an effect on cricket tubules, along with their second messenger cyclic GMP [1 mmol l^–1 8-bromo cyclic GMP (cGMP)]. The cricket kinin Achdo-KII (1 nmol l^–1; AKII) was included in the assay as a positive control. Bars represent mean values for the change in rate of secretion ( pl mm^–1 min^–1) following addition of test compounds, and vertical lines represent + 1 s.e.m. for the number of replicates indicated in parentheses. Tenmo-ADFb and 8-bromo cyclic GMP significantly increased (^***P<0.001) fluid secretion, and the response to the former was comparable to that of Achdo-KII.