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J Chem Ecol (2012) 38:13581365 DOI 10.1007/s10886-012-0200-0
Synergy Versus Potency in the Defensive Secretions from Nymphs of two Pentatomomorphan Families (Hemiptera: Coreidae and Pentatomidae)
Dorit Eliyahu & Roxanne A. Ceballos & Vahid Saeidi & Judith X. Becerra
Received: 31 January 2012 /Revised: 24 July 2012 /Accepted: 8 October 2012 /Published online: 19 October 2012 # Springer Science+Business Media New York 2012
Abstract One characteristic of true bugs (Heteroptera) is the presence of dorsal abdominal glands in the immature nymphal stages. These glands usually produce defensive chemicals (allomones) that vary among taxa but are still similar in closely related groups. Knowledge of the chemistry and prevalence of allomones in different taxa may clarify the evolution of these chemical defensive strategies. Within the infraorder Pentatomomorpha, the known secretions of nymphs of Pentatomidae tend to contain the hydrocarbon, n-tridecane, a keto-aldehyde, and an (E)-2-alkenal as the most abundant components. In the Coreidae, the dorsal abdominal gland secretions of nymphs often contain little or no hydro-carbon, and the most abundant keto-aldehyde and (E)-2-alkenal are often of shorter chain-length than those of pentatomids. We hypothesized that the long chain compounds would be less potent than their shorter homologs, and that bugs that carry the former would benefit from a synergistic effect of n-tridecane. To test this hypothesis we used three different behavioral assays with ants. A predatorprey assay tested the deterrence of allomones toward predators; a vapor experiment tested the effectiveness of allomones in the gaseous phase toward predators; and application of allomones onto predators tested the effect of direct contact. The results substantiate the hypothesis of a synergistic effect between n-tridecane and longer chain keto-aldehyde and (E)-2-alkenal in deterring predators. The short chain keto-aldehyde 4-oxo-(E)-2-hexenal was highly effective on its own. Thus, it seems that different groups of the infraorder diverged in their
strategies involving defensive chemicals. Implications of this divergence are discussed.
Keywords Allomone . Dorsal abdominal glands . Nymphs . Predators . Keto-aldehydes . n-tridecane
Introduction
The prevalence and diversity of chemical defenses in insects and other arthropods are staggering, probably more so than in any other group of terrestrial animals (Eisner, 1970). The suborder Heteroptera (Insecta: Hemiptera) is remarkable among insects in its use of defense secretions. In fact, the monophyly of the group is partly...