Revisiting the trail pheromone components of the red imported fire ant, Solenopsis invicta Buren

Abstract

Ants use species-specific trail pheromones to coordinate their sophisticated foraging behavior. During the past decades, many trail pheromone components with various structures have been identified in ants, including the red imported fire ant, Solenopsis invicta, a notorious invasive species worldwide. Four compounds, Z,E-(ZEF) and E,E-αfarnesene (EEF), Z,E-(ZEHF) and E,E-α-homofarnesene (EEHF), have been reported as components of S. invicta trail pheromone. However, another study reported an analog of α-farnesene, Z,Z,Z-allofarnesene, as a key trail pheromone component. These contrasting results caused some uncertainty about the trail pheromone composition in S. invicta. In this study, we synthesized ZEF and EEF, ZEHF and EEHF, and reanalyzed the chemicals in the Dufour gland extract and in the trail pheromone fraction of S. invicta worker body extract. The reported isomers of farnesene and homofarnesene were detected and showed trail-following activity, with ZEF as the major compound, while no allofarnesene was found, neither in the Dufour gland extract nor in the whole-body extract. Our results confirm ZEF and EEF, ZEHF and EEHF as trail pheromone components of S. invicta.

Genome-Wide Analysis of the Odorant Receptor Gene Family in Solenopsis invicta, Ooceraea biroi, and Monomorium pharaonis (Hymenoptera: Formicidae)

“…For example, trail pheromones are important for foraging behaviors in ant species. Recently, four trail pheromones, Z , E -α-farnesene (ZEF); E , E -α-farnesene (EEF); Z , E -α-homofarnesene (ZEHF); and E , E -α-homofarnesene (EEHF), were identified in S. invicta , and two of them, ZEF and EEF, mediated the mutualism between ants and aphids [ 41 ]. In addition, the trail pheromones in Myrmicine and Formicine species were identified as farnesene isomers [ 42 , 43 ], suggesting that the mechanism for recognizing trail pheromones may be similar between species.…”

Screening Universal Stress-Response Terpenoids and Their Biosynthetic Genes via Volatile and Transcriptomic Profiling in Citrus

“…50 In this study, the other 12 terpenoids but not the other two compounds were found to be significantly enriched in the field at high temperatures, which emphasized that the response compounds varied with plant species. However, (trans, trans)-α-farnesene was reported to play a role in recruiting natural enemies to defend against red ants (Formica aquilonia), 51 while Souleyre et al 52 demonstrated that reduced (trans, trans)-α-farnesene is associated with decreased disease initiation by three important postharvest pathogens. In this study, the citrus miner insect induced an increase in (trans, trans)-α-farnesene production, whereas the level of this compound decreased after infection with the citrus canker pathogen.…”

Non-consumptive effects of ant mitigate fruit damage

“…Alarm pheromones elicit aggression and attack in conspecifics, promote increased movement, gaped mandibles, sting extrusion, trail laying, and aggressive postures (Morgan 2008;Vander Meer et al 2010). Recruitment and trail pheromones from Dufour's gland organize large food retrieval, coordinate foraging and mediate mutualism with aphids (Vander Meer et al 1988, 1990Xu et al 2022). Cuticular hydrocarbons facilitate nestmate and caste recognition (Monnin 2006), and venom defends against intruders and prey (Greenberg et al 2008).…”