Origin of Pheromones

The suggestion that the sex pheromone composition of the oak leaf roller was dependent to a large extent on diet was made 82,475,476) and refuted 477, 478). It is now generally accepted that the sex pheromone of this tortricid moth species is a specific blend (67 33) of E)- - and (Z)-ll-tetradecenyl acetates 477). It is also accepted that in this species this ratio is not influenced by diet 478). However, the effects of diet on the amount of pheromonal compounds have been suggested for the summer fruit tortrix moth 479), the gypsy moth 480) and the smaller tea tortrix moth 481). 

There are cases where the host plant supplies the precursor to compounds exhibiting pheromone activity. For example, adult male danaid and ithomiine butterflies are attracted to plants containing pyrrolizidine alkaloids which they modify into dihydropyrrolizines 482—486). These substances then occur in the hairpencil secretions. 

The results obtained by Renwick et al. (579) on the exposure of adult I. paraconfusus beetles to (-1-)- and (—)-a-pinene should be reiterated. (+)-trfl 5-Verbenol and (-l-)-myrtenol were the major products in the hindgut after exposure to (+)-a-pinene whereas (-H )-m-verbenol and (-)-myrtenol were obtained after exposure to (-)-a-pinene. Therefore, variations in the enantiomeric composition of the a-pinene in trees under attack could influence the ratio of cis- to rrani-verbenol occurring in the gut of this species. 

The heteropteran, Eurygaster integriceps, uses ethyl acrylate and vanillin as components of the sex pheromone of the male 492). These compounds induce specific behavioral responses in sexually receptive females and may also act as short range attractants. Both compounds may be metabolic products from the degradation of ingested lignin 492). 

The methodology employed in the identification of pheromones is usually rigorous and precise and not subject to personal opinion. How- 

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Bartelt, R. J. and Weisleder, D. (1996). Polyketide origin of pheromones of Carpophilus davidsoni and C. mutilatus (Coleoptera Nitidulidae). Bioorganic and Medicinal Chemistry 4 429 138. 

The chemoreceptive mechanisms in amphibia are undoubtedly worthy of further analysis, not only for their own sake, but to provide clues as to the origination of advanced chemosignal systems. As noted above, a pheromonal signal from the mental gland acts as a courtship/ receptivity inducer. The plethodontid receptivity factor (PRF) (Chap. 3) despite its size (22 kD), seems to have been converted from its internal role as an inter-cellular cytokine, to an inter-individual coordinator of reproductive activity (Rollmann et al., 1999). Endocrine or... 

A question that was posed early on in determining biosynthetic pathways of the pheromones was the origin of the precursors. There was some indication that plant derived compounds could be ingested and modified by the insect into a pheromone. We now know that in some cases this occurs [7], but for the most part pheromones are biosynthesized de novo by the insect [8]. For most of the pheromones studied to date it is apparent that biosynthetic pathways of normal metabolism have been altered to produce specific pheromone components. Several enzymes in these biosynthetic pathways have been modified to produce species specific pheromone components. 

The repertoire of chemicals that can be used for communication is limited by the biosynthetic ability of the insect. Compared to other insect orders, pheromone biosynthesis in Hymenoptera has received little study [191]. However, the biosynthetic origins of chemically diverse hymenopteran semiochemicals likely include aromatic, fatty acid, and terpenoid pathways as well as simple modifications of host-derived precursors. Notable recent studies include the biosynthesis of the fatty acid components (2 )-9-oxodec-2-enoic acid 52 and (2 )-9-hydroxydec-2-enoic acid of the honeybee queen mandibular pheromone from octadecanoic acid [192,193], and the aliphatic alcohol and ester... 

After considering the evolutionary origins of the olfactory system and some basic principles of olfaction, this brief review examines one of the most extensively studied examples of neural processing of semiochemical information the sex pheromone-specific olfactory subsystem in male moths. This male-specific subsystem can be viewed as representing an exaggeration of organizational principles and functional mechanisms that are characteristic of olfactory systems in general. 

As frequently happens in science, simplicity gives way to complexity when our horizons are broadened by further research. There are now several definitions of pheromone available in the relevant literature, each more elegant than the other. However, we do not have to worry much about the arcane issues that amuse and challenge researchers in the field. For our purposes, we can pretty much do with the original definition, expanded to include a classification system. 

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 ... 

This section of the chapter summarizes recent identifications of pheromone compounds. Coverage includes from approximately the year 2000 to present. The methods are tersely described along with the compounds. The nomenclature used throughout takes the name from the original publication. The coverage is arranged based on the order of the species. 

Below is a tabular list of pheromone components that have been synthesized since 2000. This list contains the organism and the structure of the individual compounds. Also included is the name of the compound as given in the original publication. An outline of each individual synthesis is beyond the scope of this review. 

Figure 6.9 Examples of pheromone components of bark beetles (Scolytidae) and ambrosia beetles (Scolytidae and Platypodidae) classified by likely biosynthetic origin (based on Francke and Schulz, 1999). (A) References for identification and/or behavioral activity of isoprenoid pheromone compounds are as follows-. 2-methyl-3-buten-2-ol (Bakke efa/., 1977 Giesen etal., 1984 Klimetzek etal., 1989a Lanne etal., 1989), 3-methyl-3-buten-1-ol (Stoakley etal., 1978 Bowers and Borden, 1990 Bowers etal, 1991 Zhang efa/., 2000), 3-methyl-1-butanol (Renw ick etal, 1977), 3-hydroxy-3-methylbutan-2-one (Francke and Heeman, 1974 Francke etal 1974), ipsenol and ipsdienol...

Hughes P. R. (1975) Pheromones of Dendroctonus origin of a-pinene oxidation products present in emergent adults. J. Insect Physiol. 21, 687-691. 

Lu F. (1999) Origin and endocrine regulation of pheromone biosynthesis in the pine bark beetles, Ips pini (Say) and Ips paraconfusus Lanier (Coleoptera Scolytidae). PhD thesis. Univ. of Reno, Nevada, 152 pp. 

Vargo, E. L. and Hulsey, C. D. (2000). Multiple glandular origins of queen pheromones in the fire ant Solenopsis invicta. J. Insect Physiol., 46,1151-1159. 

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