Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2002
Publication Date: 10/1/2002
Citation: NELSON, D.R., OLSON, D., FATLAND, C.L. CUTICULAR HYDROCARBONS OF THE FLEA BEETLES, APHTHONA LACERTOSA AND APHTHONA NIGRISCUTIS, BIOCONTROL AGENTS FOR LEAFY SPURGE, EUPHORBIA ESULA. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY PART B. 2002. v. 133, p. 337-350. Interpretive Summary: Leafy spurge, Euphorbia esula, a native of Europe, was first reported in America in 1827 and has become a major weed in rangeland and pastures in the northern United States and southwestern Canada. Its milky latex is an irritant to cattle and horses but is tolerated by sheep and goats. In Europe, natural enemies keep the weed under control. In 1986, introduced Aphthona flea beetles were used to establish a field insectary in south central North Dakota which has provided millions of beetles for redistribution to other leafy spurge infestations in the north central Great Plains and upper Midwest. However, the beetles have not established at all sites and may be susceptible to environmental stressors such as drought and extreme heat or cold. Cuticular hydrocarbons are chemically stable, major components of the surface lipids of many species of insects and may function to prevent dessication and provide a barrier to penetration by microorganisms. Aphthona lacertosa and Aphthona nigriscutis had hydrocarbons as the major components of their cuticular surface lipids. Alkanes, alkenes and alkadienes comprised 26%, 44% and 30%, respectively for A. lacertosa, and 48%, 26% and 26% respectively for A. nigriscutis, of the total hydrocarbons. These two species were unique compared to other insects in having a high proportion of alkenes. They were unusual in the fact that they had a high proportion of alkadienes. The role of these chemicals in the survival of the species at some sites remains to be determined.
Technical Abstract: The adult beetles, Aphthona lacertosa and Aphthona nigriscutis, used as biocontrol agents for leafy spurge, had a complex mixture of hydrocarbons on their cuticular surface consisting of alkanes, methylalkanes, alkenes and alkadienes as determined by gas chromatography-mass spectrometry. In both species, the hydrocarbons were the major cuticular lipid class and the gas chromatographic profiles of the total hydrocarbons were similar. However, the profiles for the saturated hydrocarbon fraction were distinct for each species. Alkanes (n-alkanes and methyl-branched alkanes), alkenes and alkadienes comprised 26%, 44% and 30%, respectively for A. lacertosa, and 48%, 26% and 26% respectively for A. nigriscutis, of the total hydrocarbons. The major methyl-branched hydrocarbons were 2-methylalkanes: 2-methyloctacosane and 2-methyltriacontane. The major monoene was hentriacontene and the major diene was tritriacontadiene. The species were unique in that a number of di- and tri-methyl-branched alkanes were present in minor quantities in which the first methyl branch was on carbon 2 or 3. Examples of structures were 2,10-and 2,12-dimethylalkanes, 2,6- and 2,4-, and 3,7-dimethylalkanes, and 2,10,12-trimethylalkanes. A trace amount of wax esters was present.