Fluorescent insect growth regulators (FIGR) : their effects on Aedes aegypti (L) (Diptera: Culicidae), and potential use in studying insect hormone and growth regulator action

Abstract

Larvae of Aedes aegypti (L) were exposed to various compounds having fluorescent properties to determine if these compounds would elicit growth regulating effects in mosquitoes. One compound, DNSAB or 5 [[[5-(Dimethylamino)-l-naphthalenyl]sulfonyl] amino]-1,3-benzodioxole produced abnormal growth and development in these mosquitoes when all larval in stars of A. aegypti were exposed to the compound. Larvae incompletely shed their old exuviae, larval-pupal intermediates were formed, and many adults were unable to escape from their pupal skins. Methoprene [Isopropyl (2E ,4E )-11-methoxy-3,7 ,11-trimethyl-2 ,4 - dodecadienoate] and JH-I ((2E,6E,10Z)-10,11-epoxy-7-ethy1 -3 ,11-dimethyl -2 , 6-tridecadienoate) manifested their morphogenetic effects at the time of pupation. Spectral characterization of DNSAB revealed that it is well suited for use as a fluorescent biological probe. Its maximum absorption peaks are well removed from tryptophan (ca 280 nm), and its fluorescence shifts from 580 nm in buffered aqueous solution to 460 nm in cyclohexane. Also, the compound rapidly accumulated on the anal papillae and in the pharynx of larvae continuously exposed to the material. Temporal micrcopectrofluorometric studies showed that DNSAB or its metabolites accumulate heavily in the midgut and fat bodies of larval mosquitoes, especially in the membranes and fatty material of cells in these areas. Temporal exposures of larvae to 20 ppm DNSAB resulted in increased absorption of the material and increased mortality as the time of exposure was increased. Excitation and emission spectra from several larval tissues revealed peaks different from control tissue spectra and possibly indicate different binding sites of the fluorescent probe in vivo. When newly emerged adult A. aegypti were allatectomized and later injected with DNSAB, they developed eggs. This indicates that the compound should be classified as a fluorescent in sect growth regulator (FIGR)..