Chemical defense insects

Lasne M-C, Perrio C, Rouden J, Barr L, Roeda D, Dolle F, Crouzel C (2002) Chemistry of b+-Emitting Compounds Based on Fluorine-18.222 201-258 Laughrey ZR, Gibb BC (2005) Macrocycle Synthesis Through Templation. 249 in press Laurent P, Braekman J-C, Daloze D (2005) Insect Chemical Defense. 240 167-229 Lawless LJ, see Zimmermann SC (2001) 217 95-120... 

Hay ME, Duffy JE, Fenical W (1990) Host-plant specialization decreases predation on a marine amphipod an herbivore in plant s clothing. Ecology 71 733-743 Hay ME, Duffy JE, Pfister CA, Fenical W (1987) Chemical defense against different marine herbivores are amphipods insect equivalents Ecology 68 1567-1580 Hay ME, Fenical W (1992) Chemical mediation of seaweed-herbivore interactions. In John DM, Hawkins SJ, Price JH (eds) Plant-animal interactions in the marine benthos. Clarendon, Oxford, pp 319-337... 

As in other areas of natural products chemistry, studies on insect chemical defenses comprise several different aspects first come the isolation and structure determination of the compound(s) responsible for the defensive activity. The next step is the total synthesis of the identified compounds, in order to confirm the proposed structure, usually deduced from spectroscopic data only, and to get enough material for biological testing. Biosynthetic studies to determine the origin of the active compound(s) (biosynthesis by the insect itself or sequestration from the diet with or without metabolization) are sometimes performed. In some cases, the biological activities of the isolated compounds (repellency, toxicity...) and their possible pharmacological activities are also evaluated. This chapter is divided into four sections treating those different topics. 

Weatherston J, Percy JE (1970) Arthropod defensive secretions. In Beroza M (ed) Chemicals controlling insect behavior. Academic Press, New York, p 95... 

There are numerous other examples of plants, insects, large herbivores, and other organisms playing synergistic roles in nature s balance. Multiple functions are typical of plant compounds and do not contradict in any way their main role as chemical-defense and signal-induction compounds. A trait that serves multiple functions in a given plant or animal is more likely to survive the rigors of natural selection. 

The bearded dragon, Pogona vitticeps, from Australia enjoys increasing popularity as a pet in the United States. The species comes from a geographical area lacking very potent chemical defenses in insects. Consequently, the bearded... 

Valderrama, X., Robinson, J. G., Attygalle, A. B., Athula, B., and Eisner, T. (2000). Seasonal anointment with millipedes in a wild primate a chemical defense against insects. Journal of Chemical Ecology 26,2781-2790. 

Throughout history, mankind has always been interested in naturally occurring compounds from prebiotic, microbial, plants and animals sources. Various extracts of flowers, plants and insects have been used for isolating compounds whose task, color and odor could be used for various purposes. Many natural products, such as plant hormones, have a regulatory role, while others function as chemical defense against pests. The role of certain compounds is to act as chemical messengers, such as sex-attractants (pheromones) in insects, terrestrial and marine animals and humans. What is the origin of natural products ... 

The major role of chemical defenses in plants is hypothesized to be increasing the impact of insect diseases, parasites, and predators. None of these factors alone provides an explanation of why evolutionarily labile insects rarely defoliate their long-lived hosts. However, interactions among all of them could increase the useful evolutionary lifetime of each and the effectiveness of all. In particular, chemical variability is observed to place insects in compromise situations which increase their exposure and susceptibility to natural enemies. 

One must conclude that no uniform physical or chemical defense should be regarded as insurmountable by evolving insects. Any uniform chemical plant defense should select for pests capable of defeating it. Obviously, however, there is a solution... 

Resource restriction. If chemical defenses vary quantitatively within or between individual plants, then some tissues may be defended while others are not. As a result, insects have available to them the evolutionary option of avoidance they may develop the ability to recognize poor quality food and avoid it, rather than evolving detoxication mechanisms (12,18). This should result in feeding activity concentrated on a restricted set of tissues or plant individuals. There are two important consequences of this. First, contact rates with defenses can be lowered by avoiding them. Hence, the evolution of detoxication is less li)cely or less rapid (18). Second, and perhaps more important, the effectiveness of natural enemies may be enhanced (below). 

I suggest that variable plant chemistry, by restricting resource availability and focusing the activities of herbivores on a few tissues, promotes compromises between food-finding and risks from natural enemies which are not readily countered by most insects. The spatial and temporal heterogeneity which appears to be common in forest trees is the most important part of the tree s defensive system, and is the only way a plant s chemical defenses can remain effective over evolutionary time. This variable impact on natural enemies may be more important in regulating consumption than any single factor can be. 

Bowers, D. (1992). The evolution of unpalatability and the cost of chemical defense in insects. In Insect Chemical Ecology An Evolutionary Approach, eds. B. D. Roitberg and M. B. Isman, pp. 216-244. London Chapman Hall. 

Eisner, T., Eisner, M., Rossini, C. et al. (2000). Chemical defense against predation in an insect egg. Proceedings of the National Academy of Sciences, USA 97 1634-1639. 

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