Juvenile hormone is required to couple imaginal disc formation with nutrition in insects
ABSTRACT In starved larvae of the tobacco hornworm moth Manduca sexta, larval and imaginal tissues stop growing, the former because they lack nutrient-dependent signals but the latter because of suppression by juvenile hormone. Without juvenile hormone, imaginal discs form and grow despite severe starvation. This hormone inhibits the intrinsic signaling needed for disc morphogenesis and does so independently of ecdysteroid action. Starvation and juvenile hormone treatments allowed the separation of intrinsic and nutrient-dependent aspects of disc growth and showed that both aspects must occur during the early phases of disc morphogenesis to ensure normal growth leading to typical-sized adults.
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ABSTRACT: A novel technique of insect ecdysone analysis was established by capillary zone electrophoresis using 20-hydroxy ecdysone (purity >= 93%) as a standard sample. It showed that 20-hydroxy ecdysone and other trace impurities were completely separated within 5 min with an electrolyte containing 10 mmol/L borate, at pH 9.18, 20 kV applied voltage and 0.5 psi x 5 s injected volume. Under this optimal condition, effects of azadirachtin on ecdysone in the hemolymph of Ostrinia furnacalis (Guenee) were investigated. The results showed that the peak values of 20-hydroxy ecdysone were strongly suppressed by azadirachtin and the titers remained at a lower level than those in the control samples. When compared with high-performance liquid chromatography, the primary advantages of capillary zone electrophoresis include a much shorter analysis time and detection limit and the elimination of complex pretreatment of samples.Annals of the Entomological Society of America 11/2012; 105(6):890-895. DOI:10.1603/AN11177 · 1.17 Impact Factor
Article: Exaggerated Trait Growth in Insects[Show abstract] [Hide abstract]
ABSTRACT: Animal structures occasionally attain extreme proportions, eclipsing in size the surrounding body parts. We review insect examples of exaggerated traits, such as the mandibles of stag beetles (Lucanidae), the claspers of praying mantids (Mantidae), the elongated hindlimbs of grasshoppers (Orthoptera: Caelifera), and the giant heads of soldier ants (Formicidae) and termites (Isoptera). Developmentally, disproportionate growth can arise through trait-specific modifications to the activity of at least four pathways: the sex determination pathway, the appendage patterning pathway, the insulin/IGF signaling pathway, and the juvenile hormone/ecdysteroid pathway. Although most exaggerated traits have not been studied mechanistically, it is already apparent that distinct developmental mechanisms underlie the evolution of the different types of exaggerated traits. We suggest this reflects the nature of selection in each instance, revealing an exciting link between mechanism, form, and function. We use this information to make explicit predictions for the types of regulatory pathways likely to underlie each type of exaggerated trait. Expected final online publication date for the Annual Review of Entomology Volume 60 is January 07, 2014. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.Annual Review of Entomology 10/2014; 60(1). DOI:10.1146/annurev-ento-010814-021045 · 13.02 Impact Factor