Epicuticular Factors Involved in Host Recognition for the Aphid Parasitoid Aphidius rhopalosiphi

Abstract

Abstract:In insect parasitoids, fitness is dependent on the host finding and recognition abilities of the female. Host recognition cues have been described for various host-parasitoid systems, but are still under investigation in aphid parasitoids. Our study aimed to clarify the respective role of physical and chemical cues in recognition of the aphid cuticle. Shed aphid exuviae were used as an elicitor in order to avoid any influence of color, movement, or volatiles present in a living aphid. We assessed the effect of chemical and heat treatments on the texture of the cuticle by using scanning electron microscopy and tested the recognition of treated cuticles by the parasitoid. We showed that recognition cues of the cuticle can be removed chemically (using combined treatments with n-hexane and methanol). Moreover, heat treatment destroyed the physical texture of the cuticle without significantly reducing parasitoid recognition. In a second step, we showed that epicuticular extracts deposited on pieces of paper triggered female attack behavior. First results concerning the chemical composition of the active extract are presented. This study shows that chemical compounds extractable by organic solvents mediate cuticle recognition by aphid parasitoids.

Chemical cues mediating aphid location by natural enemies

“…The hexane rinse was more attractive than the ether rinse, possibly because it contained benzaldehyde, but all cuticle rinses acted as short range cues or contact semiochemicals for all natural enemies tested. Chemical and physical characteristics of the exuviae of S. avenae were described by Muratori et al (2006), who found a great variety of long hydrocarbon chains (C25 to C31), and a few wax esters, alcohols, and aldehydes (Table 1) in extractions. The extractions also elicited antennal contacts and attacks by A. rhopalosiphi, and heat treatment applied to destroy the structure of the epicuticular surface did not diminish responses, suggesting that wax structure per se does not determine host recognition.…”

“…Shed exuviae of aphids often elicit oviposition responses by parasitoids e.g. A. ervi Battaglia et al, 2000) and A. rhopalosiphi (Muratori et al, 2006).…”

“…Steidle & van Loon, 2002). For parasitoids, this final step has been divided into host recognition and host acceptance (Michaud & Mackauer, 1994;Muratori et al, 2006). A host may be recognized visually, or by antennal contact with chemical cues in the aphid cuticle.…”

Host plants and aphid hosts influence the selection behaviour of three aphid parasitoids (Hymenoptera: Braconidae: Aphidiinae)

“…Successful parasitism requires a series of interactions among parasitoids, their hosts and host plants, including habitat fi nding, host location, host acceptance, host suitability and host regulation (Vinson, 1976(Vinson, , 1984Hatano et al, 2008;Rasekh et al, 2010). Parasitoids may respond to semiochemical cues during antennal contact and ovipositor probing (Muratori et al, 2006;Larocca et al, 2007) and volatile chemical compounds emitted by damaged plants (Turlings et al, 1990, Mattiacci et al, 1994, Dicke et al, 2003. Host selection by parasitoids may be infl uenced by the insect host, the plant on which the insect hosts are feeding and by conditioning of females to the host on which they developed (Chau & Mackauer, 2001).…”

Ecological traits of a new aphid parasitoid, Endaphis fugitiva (Diptera: Cecidomyiidae), and its potential for biological control of the banana aphid, Pentalonia nigronervosa (Hemiptera: Aphididae)

“…Extensive research has been conducted on the behavior of various species of hymenopteran aphid parasitoids, from proximate (Outreman and Pierre, 2005;Henry et al, 2006;Muratori et al, 2006) to evolutionary approaches (van Alphen et al, 2003;Muratori et al, 2008a,b). With species in the genus Endaphis, we have appropriate models to address questions using comparative behavioral ecology that might lead us to greater understanding of convergence in the evolution of host exploitation (Eggleton and Belshaw, 1992;Boivin and van Baaren, 2000;Brodeur and Boivin, 2004).…”