Pheromones defense

Keywords Beetles Attractive compounds Pheromones Defensive compounds Biosynthesis Identification techniques Structure elucidation... 

The //-alkanes usually range in chain length from 21 to 31 or 33 carbons. Hydrocarbons with fewer than 20 carbons commonly occur as pheromones, defensive compounds and intermediates to pheromones and defensive compounds, but their volatility makes them unsuited to function as cuticular components, n-Alkanes have been found on almost every insect species analyzed, and can range from less than one percent of the total hydrocarbons, as in tsetse flies (Nelson and Carlson, 1986 Nelson et al., 1988) to almost all of the hydrocarbon fraction, as in the adult tenebrionid beetle, Eurychora sp. (Lockey, 1985). Depending upon the species, they can consist of essentially only one major component, such as n-pentacosane in the American cockroach, Periplaneta americana (Jackson, 1972) to a series of //-alkanes, such as the series from C23 to C33 in the housefly, Musca domes-tica (Nelson et al., 1981), with trace amounts to C37 (Mpuru et al., 2001). In all cases, the odd-numbered alkanes predominate, due to their formation from mostly two carbon units followed by a decarboxylation (Blomquist, Chapter 3, this book). Small amounts of even-numbered carbon chain //-alkanes often occur, and presumably arise from chain initiation with a propionyl-CoA rather than an acetyl-CoA. Occasionally, gas chromatographic analyses reveal similar amounts of even-numbered chain //-alkanes and odd-numbered chain components. This is a red flag that the samples must be checked for contamination. 

Ant (Formica) alarm pheromone defensive agent [toxic]... 

Alarm pheromone defensive agent Formica, ants) [toxic] Feeding deterrents (through generation of reactive isothiocyanates, R=N=C=S)... 

The first volume ends with a chapter by G. Pohnert on chemical defence in the marine environment. Defense compounds, which can be regarded as allomones, are often, but not always, more complex than other semiochemicals and may have unique modes of action. The biological mechanisms are not always easy to unravel, which is shown by some of examples. The reader may be tempted to compare the chemical complexity with that of terrestrial insect defence, which can be found in the second volume chapter by D. Daloze and J.-C. Braekman. Insects thus do not only produce interesting pheromones, but also complex allelochemicals for their own protection. 

We here summarize work we have done with a moth, Utetheisa ornatrix, that has a dependence on certain plant alkaloids. The moth uses the compounds for defense and for production of a pheromone that plays a decisive role in sexual selection. The species has a broad range, extending through North America east of the Rockies and southward into Brazil, Argentina, and Chile. Our studies were done mostly with populations of the moth from central Florida. 

Another dictyotalean genus, Dictyopteris, has been reported to produce an array of Cu cyclic or acyclic acetogenins derived from higher fatty acids (Stratmann et al. 1992). Examples include the hydrocarbons dictyopterene A (Fig. 1.6e) (Moore et al. 1968) and dictyopterene D [B1] (Fig. 1.6f) (Moore and Pettus 1971), which act as pheromones in sexual reproduction (Stratmann et al. 1992). The compounds are short lived and undergo facile degradative oxidation to yield compounds such as dictyoprolene (Fig. 1.6g) (Yamada et al. 1979) and dihydrotropone (Fig. 1.6h) (Moore and Yost 1973). In a tme exhibition of efficiency, these degradative products have also been shown to act as a chemical defense (Hay et al. 1998). 

Pohnert G (2004) Chemical defense strategies of marine organisms. In The chemistry of pheromones and other semiochemicals I. Topics in current chemistry, vol 239. Springer, Berlin, pp 179-219... 

Keywords Heteroptera Pheromone Allomone Semiochemical Chemical defenses... 

Alarm pheromones, consisting of typical components of bug defensive secretions (e.g., simple aldehydes and esters), have been reported for Leptoglos-sus zonatus [122] and Leptocorisa oratorius [123]. 

The pheromone of Leptocorisa chinensis illustrates the critical importance of the interplay between attractive and inhibitory chemicals [21]. Headspace extracts from males and females were qualitatively similar. From the eight compounds in headspace extracts that elicited strong antennal responses from males, four were discounted as being defensive chemicals or alarm pheromones. The remaining group of four chemicals, consisting of octanol,... 

Second, in tandem with better analytical methods, as our knowledge of bug defensive chemistry increases through the identification of compounds from an increasing number of species, it will become easier to discern potential pheromone components against the background of common defensive chemicals that are shared by multiple species. 

Abstract This chapter reviews chemical structures of biologically active, volatile compounds in beetles. Techniques used for structure elucidation are briefly discussed as well as facts and speculations on the biosynthesis of target compounds. Syntheses of selected substances are cursorily presented. The order of sections follows taxonomic classifications. Depending on the biological significance of relevant compounds in certain taxa, the corresponding sections are again subdivided into attractive compounds (mostly intraspecifically active pheromones) and defensive compounds (mostly interspecifically active allomones). 

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