Deterrence, principle

One example for a chemically defended zooplankton species is the Antarctic pteropod Clione antarctica. This shell-less pelagic mollusk offers a potentially rich source of nutrients to planktivorous predators. Nonetheless fish do not prey on this organism, due to its efficient chemical defense. In a bioassay-guided structure elucidation, pteroenone 37 could be isolated and characterized as the main defensive principle of C. antarctica [82,83]. If embedded in alginate, this compound is a feeding-deterrent in nanomolar concentrations. This unusual metabolite is likely to be produced by C. antarctica itself and not accumulated from its food, since its major food sources did not contain any detectable quantities of 37. 

The fundamental need to characterise and quantify bacterial strains in natural biofilms in order to understand their potential role as producers of settlement signals highlights the need for molecular techniques which can be used to identify and quantify bacteria in situ. For example, low abundance of putatively deterrent bacterium on surfaces in situ may preclude the production of sufficient quantities of deterrent metabolites. Appropriate techniques for such characterization include denaturing gradient gel electrophoresis (DGGE)107 and fluorescence in situ hybridization (FISH)108 and would in principle allow for the detection and quantification of all species in the biofilm. 

This utility reflected both the inability of the Abyssinians to protect themselves and the absence of any credible deterrent. The Italians were neither threatened with serious retaliation by the Abyssinians nor with intervention by other powers. Only Britain and France could have posed any threat but neither was prepared to act against Italy, a Locarno power, to uphold the principle of collective security. Although the League of Nations had responded to Italy s invasion by imposing economic sanctions (18 November 1935), it could never... 

This is the law of offences (i.e. crimes) against the state and those under its protection. Prosecution is usually started by the state and it aims to punish and to act as a deterrent through fines, imprisonment, orders and disqualification from holding office. Guilt is determined through the application of the beyond all reasonable doubt principle. 

Since it is generally accepted that secondary plant constituents basically owe their existence to the selection by herbivores, microorganisms, etc., the dichotomy between alkaloids and tannins called for an explanation. To this end, various hypotheses were offered, which have been reviewed by Feeny (20). One was the "apparency hypothesis", which claimed that the more "apparent" or "predictable and available" plants should depend more on "quantitative" defense, i.e. tannins and other polyphenols, which were considered to be in principle non-detoxifiable. "Qualitative defense" involving smaller quantities of toxins such as alkaloids would then be the viable option for "unapparent" plants. However, these concepts have not been fully supported by observed patterns of predation. It seems that dso the postulated effects of tannins can be circumvented by various metabolic properties of the herbivore, and some tannins seem to be directly toxic to some consumers, in contrast to earlier postulates. Nonetheless, many recent studies have strengthened the view that tannins can act as strong deterrents for herbivores, perhaps because of their association with foliage of poor quality. 

P. J. Weldon and J. F. Carroll, Vertebrate chemical defense Secreted and topically acquired deterrents of arthropods. Chapter 3, pp. 47-75, in Insect Repellents Principles, Methods, and Uses, ed. by M. Debboun, S. P. Frances, and D. Strickman, Boca Raton, FL CRC Press, 2007. 

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