Mating Status of an Herbivorous Stink Bug Female Affects the Emission of Oviposition-Induced Plant Volatiles Exploited by an Egg Parasitoid

Abstract

Insect parasitoids are under selection pressure to optimize their host location strategy in order to maximize fitness. In parasitoid species that develop on host eggs, one of these strategies consists in the exploitation of oviposition-induced plant volatiles (OIPVs), specific blends of volatile organic compounds released by plants in response to egg deposition by herbivorous insects. Plants can recognize insect oviposition via elicitors that trigger OIPVs, but very few elicitors have been characterized so far. In particular, the source and the nature of the elicitor responsible of egg parasitoid recruitment in the case of plants induced with oviposition by stink bugs are still unknown. In this paper, we conducted behavioral and molecular investigations to localize the source of the elicitor that attracts egg parasitoids and elucidate the role of host mating in elicitation of plant responses. We used as organism study model a tritrophic system consisting of the egg parasitoid Trissolcus basalis , the stink bug host Nezara viridula and the plant Vicia faba . We found that egg parasitoid attraction to plant volatiles is triggered by extracts coming from the dilated portion of the stink bug spermathecal complex. However, attraction only occurs if extracts are obtained from mated females but not from virgin ones. Egg parasitoid attraction was not observed when extracts coming from the accessory glands (mesadene and ectadene) of male hosts were applied, either alone or in combination to plants. SDS-PAGE electrophoresis correlated with olfactometer observations as the protein profile of the dilated portion of the spermathecal complex was affected by the stink bug mating status suggesting post-copulatory physiological changes in this reproductive structure. This study contributed to better understanding the host location process by egg parasitoids and laid the basis for the chemical characterization of the elicitor responsible for OIPV emission.

Field collection of egg parasitoids of Pentatomidae and Scutelleridae in Northwest Italy and their efficacy in parasitizing Halyomorpha halys under laboratory conditions

“…Recent research has focused on chemical ecology, that is, the emission by plants of volatile compounds in response to herbivory and egg deposition, which could affect the behavior of natural enemies, just as (volatile) compounds from herbivores themselves. A particular focus has been the interaction between N. viridula and T. basalis (Colazza et al, 2004, 2007; Salerno et al, 2006, 2019). In our study in Northwest Italy, T. basalis was the only scelionid species associated with N. viridula , consistent with observations from central Italy (Colazza & Bin, 1995), whereas other parasitoid species emerged from field‐collected eggs in other areas (Jones, 1988; Corrêa‐Ferreira & Moscardi, 1996).…”

Dynamic environmental interactions shaped by vegetative plant volatiles

“…Recently, four oligosaccharides detected in the oral secretions of the cotton leafworm ( Spodoptera littoralis ) larvae induced volatile emissions in Tansy ( Tanacetum vulgare ) plants. 68 Herbivore-derived proteins from eggs 69,70 and frass 71 modulate volatile emissions as well. For instance, an annexin-like protein “diprionin” isolated from egg-associated secretions in sawfly ( Diprion pini ) was recently found to trigger ( E )-β-farnesene emission in Scots pine ( Pinus sylvestris ).…”

Biological control of invasive stink bugs: review of global state and future prospects

“…For example, Tr. basalis (Colazza et al, 2004a,b; Frati et al, 2017; Salerno et al, 2019) and Te. podisi (Blassioli Moraes et al, 2005, 2009; Michereff et al, 2011) are attracted to leguminous plants infested by N. viridula or E. heros , respectively.…”