Content area
Full text
J Chem Ecol (2012) 38:10501056 DOI 10.1007/s10886-012-0166-y
Defensive Roles of (E)-2-Alkenals and Related Compounds in Heteroptera
Koji Noge & Kathleen L. Prudic & Judith X. Becerra
Received: 12 November 2011 /Revised: 4 April 2012 /Accepted: 7 July 2012 /Published online: 25 July 2012 # Springer Science+Business Media, LLC 2012
Abstract We examined whether shared volatiles found in various heteropteran species and developmental stages function to repel predators. The nymphal dorsal abdominal gland secretions of Riptortus pedestris (Heteroptera: Alydidae) and Thasus acutangulus (Heteroptera: Coreidae), and the metathoracic scent gland secretion of Euschistus biformis (Heteroptera: Pentatomidae) adults were identified by gas chromatography/mass spectrometry (GC/MS). (E)-2-Hexenal, 4-oxo-(E)-2-hexenal (4-OHE), and (E)-2-octenal were found in all three species and deemed likely candidates for repelling predators. In addition to (E)-2-alkenals, the adult E. biformis secreted (E)-2-hexenyl acetate, (E)-2-octenyl acetate, and four hydrocarbons. We evaluated the potential predator repellent properties of these compounds and compound blends against a generalist, cosmopolitan insect predator, the Chinese praying mantid (Mantodea: Mantidae: Tenodera aridifolia sinensis). Mantids that experienced (E)-2-hexenal, (E)-2-octenal, and (E)-2-octenyl acetate moved away from the site of interaction, while 4-OHE and (E)-2-hexenyl acetate did not affect mantid behavior. The compound blends did not have additive or synergistic
repellency effects on predator behavior. Compound repellency was not related to compound volatility. Instead, the repellent effect is likely related to predator olfaction, and the affinity of each compound to receptors on the antennae. Our results also suggest the repellents might intensify the visual defensive signals of aposematism (T. acutangulus nymphs) and mimicry (R. pedestris nymphs) in heteropteran bugs.
Keywords Olfactory repellency . Thasus acutangulus . Euschistus biformis . Riptortus pedestris . Riptortus clavatus . (E)-2-hexenal . (E)-2-octenal . (E)-2-octenyl acetate . Aposematism . Mimickry . Soybean pest
Introduction
Repellent chemicals discourage the receiver from further interaction with the signaler, for example, unwanted pollinators, predators, or mates. Repellents interact with the olfactory system eliciting a negative behavior in the receiver such as fleeing or bypassing prey, but do not often result in the death of the receiver (Bowers, 1993; Chapman, 1998; Ruxton et al., 2004). In predatorprey interactions, these compounds are often generalist signals emitted by the prey communicating information to a variety of predator species with varying sensory capabilities. Thus, anti-predator compounds are more likely to...