Insect ecdysis

Figure 15. 3-Deacetylazadirachtinol, a Potent Insect Ecdysis Inhibitor Isolated from the Seeds of Azadirachta indica (57)...

Isolation of Phytoecdysones as Insect Ecdysis Inhibitors and Feeding Deterrents... 

Figure 9. Structure of the llmonold, cedrelone, the toxicity of which Included Insect ecdysis Inhibition.

Kubo, I. and J. Klocke, Insect ecdysis inhibitors, in Natural Resistance of Plants to Pests (M. B. Green and P. A. Hedin, eds.), ACS Symposium Series 296, 206-219, American Chemical Society, Washington, DC, 1986. 

Insect Growth Regulators. These compounds (40—45), unlike most conventional insecticides, interfere with biochemical processes that are unique to arthropods eg, molting, ecdysis, and formation of the chitinous exoskeleton. Therefore, they are selective insecticides with very low mammalian toxicity. 

Figure 2. A molting cycle failure of the silkworm, Bombyx mori, caused by ingestion of the crude methanol extract of Ajuga remota root. The insect underwent normal apolysis, but failed to complete ecdysis. Thus, it could not remove its head capsule or its trunk exuviae. Magnification X11.

Insect growth regulation involving such processes as water balance or ecdysis (moulting) are processes that are insect specific but are also fundamental to insect survival. Another is chitin biosynthesis, as chitin is a major component of the insect cuticle. 

Chitin Synthesis Inhibitors. These are insect growth regulators that prevent the formation of the insect chitinous exoskeleton and thus produce a critical biochemical lesion during hatching, ecdysis, or pupation (44). These complex biochemical and physiological processes are unique to arthropods therefore, the benzoyl phenyl ureas are highly specific insecticides (44). 

Insects Locusta migratoria100—brown crop fluid 64,000 green crop fluid 4000-14,000 hemolymph 300 ecdysial fluid, trace. Drosophila melanogaster embryo6108 6000. 

If the compound is causing the insect to be stressed or intoxicated, the insect larva (in this case a prepupa) may have trouble casting the old cuticle, yet be capable of tanning. Thus, the insect becomes a tanned larva or what appears to be a half pupa/half larva (due, in part, to incomplete ecdysis). For example, larvae treated with paraoxon (200 nmol./larva data not included in Table I due to high mortality) caused the formation of tanned larvae in all larvae treated. However, all of these larvae had obviously been adversely affected (intoxicated) by the paraoxon... 

These molecules were shown to be potent inhibitors of chitinase, an enzyme involved in the ecdysis of many insects and crustaceans, whose inhibitors are supposed to control the settlement of barnacles and, therefore, could have a potential application as antifouling agents. Unfortunately, no data are available in the literature about cytotoxic, immunosuppressive, or antibacterial activities of styloguanidines and, thus, a comparison with the potently bioactive congeners palau amines is not possible. 

For behavior to be adaptive, it must be adjusted to fit the changing physiological and developmental conditions of the animal. Neuropeptides are a class of molecules that play an important role in these behavioral adjustments. The ecdysis system of insects has provided a useful model for examining the manner by which neuropeptides alter the functional state of the nervous system. 

Eclosion hormone is a unique neuropeptide whose actions are tied to a specific set of behaviors shown at ecdysis. The hormone, in turn, is produced by a gene whose sole product is EH. This gene occurs throughout the insects, and the association of EH with ecdysis behaviors may be an evolutionarily ancient relationship. An intriguing aspect of EH is the small number of neurons that actually express the... 

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