Arctiid pheromones

Several families of moths utilize hydrocarbons or epoxides of hydrocarbons as their sex pheromone. Oenocyte cells produce hydrocarbons that are transported through the hemolymph by lipophorin [71]. In a study using arctiid moths it was shown that sex pheromone hydrocarbons are transported on the same lipophorin particle as the hydrocarbons destined for the cuticular surface [ 17]. Therefore, specific uptake of the sex pheromone hydrocarbon occurred in pheromone glands [17]. Similar findings have been found with other moths [72-74]. The mechanism behind this specific uptake of one hydrocarbon from a potential pool of other hydrocarbons is unknown. 

Some male arctiid moths produce their courtship pheromone from dietary pyrrolizidine alkaloids acquired during feeding by the larvae [ 126]. Conversion of monocrotaline to hydroxydanaidal by males is accomplished by aromatiza-tion, ester hydrolysis and oxidation of an alcohol to the aldehyde [7]. In the case of Utetheisa ornatirx the stereo-configuration at C7 of the dietary alkaloid is the same as the pheromone released (R). In contrast, another arctiid, Creatono-tos transiens, can convert a dietary precursor alkaloid with the (S) configuration at C7 (heliotrine) to (l )-hydroxydanaidal. The biosynthesis occurs by first oxidation-reduction at C7 to convert the stereochemistry and then proceeds through aromatization, hydrolysis, and oxidation [7]. 

FIGURE 1 Female arctiid moth in a wind tunnel. Pheromone emission as a visible stream of liquid droplets is shown. Photo by S. Krasnoff. 

Bell, T. W. and Meinwald, J. (1986). Pheromones of two arctiid moths (Creatonotos transiens and C. gangis) chiral components from both sexes and achiral female components. Journal of Chemical Ecology 12 385 109. 

Bell, T. W Boppre, M., Schneider, D. and Meinwald, J. (1984). Stereochemical course of pheromone biosynthesis in the arctiid moth, Creatonotos transiens. Experientia 40 713-714. 

Conner, W. E., Eisner T., Vander Meer, R. K., Guerrero, A. and Meinwald, J. (1981). Precopulatory sexual interactions in an arctiid moth (Utetheisa ornatrix) role of pheromone derived from alkaloids. Behavioral Ecology and Sociobiology 9 227-235. 

Conner, W. E. Roach, B., Benedict, E., Meinwald, J. and Eisner, T. (1990). Courtship pheromone production and body size as correlates of larval diet in males of the arctiid moth, Utetheisa ornatrix. Journal of Chemical Ecology 16 543-551. 

Evolutionary trends in the male pheromone systems of arctiid moths evidence from studies of courtship in Phragmatobia fuliginosa and Pyrrharctia isabella (Lepidoptera Arctiidae). Zoological Journal of the Linnaean Society 99 319-338. 

Krasnoff, S. B. and Yager, D. D. (1988). Acoustic response to a pheromonal cue in the arctiid moth Pyrrharctia isabella. Physiological Entomology 13 433 140. 

Meyer, W. (1984). Sex pheromone chemistry and biology of some arctiid moths... 

Wink, M. L Schneider, D. and Witte, L. (1988). Biosynthesis of pyrrolizidine alkaloid-derived pheromones in the arctiid moth, Creatonotos transiens stereochemical conversion of heliotrine. Zeitschrift fiir Naturforschung 43c 737-741. 

Charlton R. E. and Roelofs W. L. (1991) Biosynthesis of a volatile, methyl-branched hydrocarbon sex pheromone from leucine by Arctiid moths (Holomelina spp.). Arch. Insect Biochem. Physiol. 18, 81-97. 

Availability of biosynthetic precursors from food, as in some danaid butterflies and arctiid moths, which modify plant pyrrolizidine alkaloids into volatile derivatives that are used as male pheromones (e.g. Schneider et al., 1975). In... 

J. (1983). Polyene pheromone components from an arctiid moth (Utetheisa ornatrix) Characterization and synthesis. J. Org. Chem., 48, 2266-2270. 

Almost all known Type II pheromones are listed in Tables 18.1-18.4 (Arctiids, Geometrids, Noctuids, and Lymantriids, respectively). The few exceptions where Type II pheromones have been found in other lepidopteran families (e.g., Crambidae or Pyralidae) are discussed in the section below on taxonomic distribution of these compounds. 

Table 18.1 Known and possible female-produced sex pheromone components for arctiid moths. Compounds in bold have been found in pheromone gland extracts or aeration extracts and have been shown to be active in behavioral bioassays or field trials compounds in normal font have been found in pheromone gland or aeration extracts and compounds in italics have been shown to attract males infield screening trials.

Recent studies have provided additional details of Type II pheromone biosynthesis in two other arctiid species. For example, injection of labeled 9Z,12Z,15Z-18 COOH into pupae of female Utetheisa ornatrix resulted in incorporation of label into 3Z,6Z,9Z-21 H as expected, and also into 1,3Z,6Z,9Z-21 H (Choi etal., 2007), supporting the chain elongation... 

In contrast, the hemolymph of females of the arctiid moth Spilosoma imparilis were found to contain significant levels of the polyunsaturated hydrocarbons corresponding to the epoxide pheromone components produced by this species (Wei el al., 2003). In a biosynthetic study with the arctiid Syntomoides imaon, the pheromone of which consists of a blend of 3Z,6Z,9Z-21 H and 1,3Z,6Z,9Z-21 H (Matsuoka el al., 2008), the lipids extracted from oenocytes and peripheral fat bodies associated with the abdominal integument contained both (llZ,14Z,17Z)-eicosa-ll,14,17-trienoic acid and (13Z,16Z,19Z)-docosa-13,16,19-trienoic acid, the intermediates predicted by elongation of linolenic acid by one or two cycles of 2-carbon chain extension (Ando et al., 2008). The latter acid is likely to be the direct biosynthetic precursor to 3Z,6Z,9Z-21 H (Ando et al., 2008). 

In a parallel study, Wei et al. (2003) showed that the triene precursors to epoxide pheromones were present, along with a variety of other hydrocarbons, in extracts of hemolymph from females of two geometrid (A. selenaria cretacea and II. artilineata) and one arctiid species (Spilosoma imparilis). The epoxides were not found in the hemolymph extracts, nor were the trienes found in extracts of hemolymph from males. When labeled trienes were injected into the abdomens of females, labeled epoxides were later recovered from pheromone glands, demonstrating that the injected compounds had been transported to and taken up by the glands, and that triene hydrocarbons, synthesized somewhere outside the glands (probably in oenocytes), were the direct precursors to the epoxide pheromone components. 

In the final installment of this story to date, Matsuoka et al. (2008) determined that female A. selenaria cretacea contained (llZ,14Z,17Z)-eicosa-ll,14,17-trienoic acid but not the longer-chain (13Z,16Z,19Z)-docosa-13,16,19-trienoic acid, in line with the fact that the pheromone of this species consists of 3Z,6Z,9Z-19 H and a corresponding monoepoxide (Matsuoka et al., 2008). That is, this geometrid only requires a C20 fatty acid precursor to decarboxylate to its C19 pheromone compounds. In contrast, as mentioned above, the arctiid species Syntomoides imaon, which produces C2i triene and tetraene pheromone components, was found to contain both (llZ,14Z,17Z)-eicosa-ll,14,17-trienoic acid and the longer-chain (13Z,16Z,19Z)-docosa-13,16,19-trienoic acid (Matsuoka et al., 2008). That is, the arctiid species requires the C22 precursor in order to produce its C21 pheromone components by decarboxylation, whereas the geometrid species only requires the C20 precursor, because its pheromone is composed of the shorter-chain C19 compounds. These data suggest that the chain elongation of linolenic acid and related precursors is under precise control. 

Pheromones. 97. The sex pheromone complex of the female arctiid moth Tyria jacobaeae (Lepidoptera, Arctiidae). Z. Naturforsch. C, 49, 276-279. 

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