Chemical Ecology The Chemistry of Biotic Interaction (1995) / Chapter Skim
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The Chemistry of Sex Attraction
The Chemistry of Sex Attraction
Pages 103-118
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From page 103... ...
The Chemistry of Gamete Attraction /101 observed ire the range of 1-1000 pmol. The blends may contain various configurational isomers of the genuine pheromones as well as mixtures of enantiomers.
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From page 104... ...
102 / Wilhelm Boland 26. Muller, D
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From page 105... ...
The phenomenon of virgin female moths attracting large numbers of male moths was noted long before it was understood that a trail of chemicals could be so effective over great distances.
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From page 106... ...
Research efforts have focused on the overt chemical signals used in the mating process, with the driving force and financial backing for much of the research due to the potential for use of synthetic pheromone chemicals in pest control programs. This effort has resulted in the identification of sex attractants for >1600 insect species from >90 families in nine orders, with an emphasis on Lepidoptera (21.
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From page 107... ...
The sensitivity and specificity of the male's antenna to its own pheromone components made it a powerful tool in assaying for pheromone components and in predicting their structures (6~. GLC retention times on nonpolar and polar columns of active compounds in crude female gland extracts could be determined quickly by collecting the GLC effluent in a separate capillary tube each minute and puffing air through each tube and across an isolated male antenna in the EAG setup.
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From page 108... ...
. The EAG technique as a bioassay tool for active fractions has been used in the identification of sex pheromones of many insect species in several orders and remains as a key factor in the identification of pheromones.
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From page 109... ...
Single complex chemicals indeed have been found that elicit the full repertoire of behavioral responses at very low biologically meaningful concentrations. The cockroach sex pheromones (Figure 2)
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From page 110... ...
can be determined easily from the cascade of acyl intermediates produced by the l\~-desaturase and chain-shortening reactions (Figure 31. SEX PHEROMONE PRODUCTION Key Biosynthetic Enzymes The overt chemical signals are only part of the chemistry involved in the overall communication system.
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From page 111... ...
As shown above with the cabbage looper moth, a unique A~-desaturase is found in lepidopteran sex pheromone glands to produce a whole variety of precursors in combination with chain-shortening reactions, followed by the action of reductases and acetyltransferases to produce the acetate pheromone components. The enzymes themselves are only part of the chemistry involved at this stage.
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From page 112... ...
In the redbanded leafroller moth, it was shown that PBAN from the brain stimulates the release of a different peptide from the bursae copulatrix that is used to stimulate pheromone production in the pheromone gland found at the posterior tip of the abdomen (24~. The chemistry involved in the mode of action of PBAN is complex and still under investigation, but present studies have shown that PBAN can interact directly with the pheromone gland and apparently stimulates pheromone biosynthesis by activating a plasma membrane calcium channel that regulates production of cAMP (25)
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From page 113... ...
One additional factor that comes into play in the overall chemistry of the communication system relates to chemical signals from host plants that can override the photoperiodic control of phermone production. With the corn earworm, it was found that a volatile chemical signal from corn silk, probably ethylene, was required by wild insects for stimulation of pheromone production (33~.
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From page 114... ...
With moths, it has been found that the pheromone chemicals do not actually attract a mate by means of a chemical gradient, but rather the correct blend and abundance of pheromone molecules in a fluctuating plume will turn on two programs, optomotor anemotaxis and self-steered counterturning, in flying male moths and mediate flight upwind to the odor source (391. Detection of pheromone, thus, turns on a visually guided motor program that produces upwind surges by the male moth, and when the signal is lost, the male stops upwind flight and the counterturning program causes it to cast sideways back and forth until the chemical signals are once again detected.
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From page 115... ...
appears to function in the central nervous system and is not linked with the autosomal factor whose product effects different electrophysiological responses to pheromone components in antenna! olfactory cells or with the autosomal factor controlling pheromone blend composition.
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From page 116... ...
SUMMARY The chemical communication system used to attract mates involves not only the overt chemical signals but also indirectly a great deal of chemistry in the emitter and receiver. As an example, in emitting female moths, this includes enzymes (and cofactors, mRNA, genes)
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From page 117... ...
Input from the hundreds of thousands of sensory cells is processed and integrated with other modalities in the central nervous system, but many unknown factors modulate the information before it is fed to motor neurons for behavioral responses. An unknown brain control center for pheromone perception is discussed relative to data from behavioral-threshold shoddies showing modulation by biogenic amines, such as octopamine and serotonin, from genetic studies on pheromone discrimination, and from behavioral and electrophysiological studies with behavioral antagonists.
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From page 118... ...
116 / Wendell L Roelofs 13.
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