A chitin-like component in Aedes aegypti eggshells, eggs and ovaries

• Published in: Insect biochemistry and molecular biology 2007-12, Vol.37 (12), p.1249-1261
• Main Authors: Moreira, Mônica F., dos Santos, Amanda S., Marotta, Humberto R., Mansur, Juliana F., Ramos, Isabela B., Machado, Ednildo A., Souza, Gustavo H.M.F., Eberlin, Marcos N., Kaiser, Carlos R., Kramer, Karl J., Muthukrishnan, Subbaratnam, Vasconcellos, Ana Maria H.
• Format: Article
• Language: English
• Subjects: Aedes - drug effects; Aedes - enzymology; Aedes - metabolism; Aedes aegypti; Animals; Bacillus circulans; Benzamides - pharmacology; Benzoylphenylurea; chemical composition; Chemical control; Chitin; Chitin - antagonists & inhibitors; Chitin - biosynthesis; Chitin staining; chitin synthesis inhibitors; chitinase; Chitinases - metabolism; chorion; egg hatchability; Eggshell; Female; glucosamine; Insect growth regulator; Insecticides - pharmacology; Larva - drug effects; Lufenuron; Mosquito; mosquito control; oocytes; oogenesis; ova; ovarian development; Ovaries; Ovary - metabolism; Ovum - drug effects; Ovum - enzymology; Ovum - metabolism; Spectrometry, Mass, Electrospray Ionization; Streptomyces griseus
• ISSN: 0965-1748; 1879-0240
• DOI: 10.1016/j.ibmb.2007.07.017

An insoluble white substance was prepared from extracts of eggshells of Aedes aegypti, the yellow fever mosquito and dengue vector. Its infrared and proton NMR spectra were similar to that of standard commercial chitin. This putative chitin-like material, also obtained from ovaries, newly laid and dark eggs, was hydrolyzed in acid and a major product was identified by HPLC to be glucosamine. The eggshell acid hydrolysate was also analyzed by ESI-MS and an ion identical to a glucosamine monoprotonated species was detected. The presence of chitin was also analyzed during different developmental stages of the ovary using a fluorescent microscopy technique and probes specific for chitin. The results showed that a chitin-like material accumulates in oocytes during oogenesis. Streptomyces griseus chitinase pre-treatment of oocytes greatly reduced the chitin-derived fluorescence. Chitinase activity was detected in newborn larvae and eggs prior to hatching. Feeding experiments indicated that the chitin synthesis inhibitor lufenuron inhibited chitin synthesis, either when mosquitoes were allowed to feed directly on lufenuron-treated chickens or when an artificial feeding system was used. Lufenuron inhibited egg hatch, larval development and reduced mosquito viability. These data demonstrate for the first time that (1) a chitin-like material is present in A. aegypti eggs, ovaries and eggshells; (2) a chitin synthesis inhibitor can be used to inhibit mosquito oogenesis; and (3) chitin synthesis inhibitors have potential for controlling mosquito populations.