Dual control of pupal diapause by cyclic nucleotides in the bertha armyworm, Mamestra configurata Wlk.

Abstract

Treatment of diapausing pupae of M. configurata with dibutyryl cyclic AMP or 8-(4-chlorophenylthio) cyclic AMP (CPT cyclic AMP) reduced the incidence of eclosion to zero compared to about 15% for controls, whereas treatment with cyclic GMP increased eclosion to more than 90%. Treatment with the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) resulted in a high incidence (79.8%) of eclosion, but treatment with dibutyryl cyclic AMP + IMBX or CPT cyclic AMP + IBMX gave low incidences (<9.1%) of eclosion. Other methylxanthines (theophylline, 8-phenyltheophylline, caffeine) and papaverine had relatively little effect on eclosion even at high doses. Treatment of post-diapause pupae with dibutyryl cyclic AMP or CPT cyclic AMP resulted in a low incidence (<5.0%) of eclosion compared to 98.8% eclosion in controls. Suppression of eclosion was more effective if dibutyryl cyclic AMP was given within the first 2 days of pupal-adult development at 20°C and became less effective as development progressed, indicating that dibutyryl cyclic AMP inhibits endocrine events initiating development rather than inhibiting subsequent metamorphic development. Treatment of post-diapausing pupae with cyclic GMP, IBMX, other methylxanthines or papaverine did not affect eclosion. These results are consistent with a dual control of pupal diapause in M. configurata by cyclic nucleotides, with cyclic AMP acting to maintain diapause and cyclic GMP acting to terminate it.