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La phéromone d'alarme chez les femelles du frelon invasif Vespa velutina nigrithorax
- 1. Highlight on the complex composition of Vespa velutina nigrithorax venom gland Journées GDR MediatEC 2021 Berville L, Lucas C, Haouzi M, Khalil A, Gévar J, Bagnères A-G, Darrouzet E
- 2. CONTEXT INVASIVE SPECIES: New constituent of ecosystems Permanently modifying the distribution and diversity of natural life CONSIDERABLE DECLINE IN POLLINATORS: land-use, urbanisation, which result in the loss and degradation of natural habitats disappearance of diverse flora, reducing food and nesting resources PESTICIDES: directly (insecticides and fungicides) and indirectly (herbicides) CHANGING CLIMATE : SOCIAL INSECTS: Considered to be the most successful invaders Excellent dispersal and competitive abilities Effective defenses & High reproduction rates diets ranges & broad habitat
- 3. Vespa velutina nigrithorax 10 years Transport Introduction •Reproduce •Spread Establishment Dominate community
- 4. IMPACTS • Direct economic impacts • large impacts to honeybee populations => honey production • Indirect economic impacts • loss of ecosystem services • Direct environmental impacts • Predation on severals insects and arthropod taxa • Risk for human health
- 5. GOALS • The hornets persistence has inspired the development of control methods • Induce significant ecological impacts => lack of species-specificity • Hornet NestTreatment • Insecticide CURRENT PRACTICE News species-specific trapping systems based on pheromones are ongoing developments
- 6. CURRENT PRACTICE • Chemical signals, like pheromones, often trigger different behaviors like : • Recruitment, • Dispersal, • Aggressiveness, • Aggregation ➢ Alarm pheromones are key importance o Multi-components blends o Highly volatile ➢ Venom glands are often the primary source (wasps & hornet) 2 studies presented the evidence of the alarm pheromone in both V. velutina auraria & V. v. nigrithorax (Cheng et al. 2017 & Thiery et al. 2018)
- 7. Gynes Foundresses Queens Workers Stressed workers May / June June / August May / August May / August Our goal was to clarify the composition of the invasive species’ alarm pheromone and to assess differences in chemical profiles among queens, foundresses, pre wintering gynes, and workers.
- 8. Pre wintering gynes Foundresses Queens Workers Stressed workers GOALS : composition of the volatile molecules produced by females May / August
- 9. W G F Q a. 5 venom sacs were pooled b. 1 ml of heptane c. 2 µL gland’s extract were analyzed First Experiment : composition of the volatile molecules produced by females x15 x8 x6 x6
- 10. 38 compounds with chain lenghs from 10 to 16 carbons 26 peaks presented an average relative area bigger than 0,5% First Experiment : composition of the volatile molecules produced by females Workers PW gynes Foundresses Queens
- 11. 26 COMPOUNDS • Gynes & foundresses • 25 : Queens • 23 : Workers 11 ketones 8 Esters 3 Alcohols 3 unknowns RESULTS 28 % of the total blend • 4,8 DiMe-7-nonen-2-one First Experiment : composition of the volatile molecules produced by females 10 news molecules • Between C10 and C16 Workers PW gynes Foundresses Queens
- 12. 26 COMPOUNDS • Gynes & foundresses • 25 : Queens • 23 : Workers RESULTS Queens Workers PW gynes Foundresses P1Q P2Q P3Q P4Q P5Q P6Q P1F P3F P2F P4F P5F P6F P1O P2O P3O P4O P5O P6O P7O P8O P9O P10O P11O P12O P13O P14O P15O P1G P2G P7G P6G P5G P4G P3G -4 -2 0 2 4 Factor 1: 38,82% -4 -3 -2 -1 0 1 2 3 4 Factor 2: 19,55% P1Q P2Q P3Q P4Q P5Q P6Q P1F P3F P2F P4F P5F P6F P1O P2O P3O P4O P5O P6O P7O P8O P9O P10O P11O P12O P13O P14O P15O P1G P2G P7G P6G P5G P4G P3G a b c d e f g h i j k l m n o p q r s t u v w x y z -1,0 -0,5 0,0 0,5 1,0 -1,0 -0,5 0,0 0,5 1,0 a b c d e f g h i j k l m n o p q r s t u v w x y z First Experiment : composition of the volatile molecules produced by females The ellipses indicate the 95% confidence limit of the data. GROUPS 3 • Workers and Gynes : NS
- 13. Gynes Foundresses Queens Workers Stressed workers & gynes GOALS : composition of the volatile molecules produced by females
- 14. a. 4 living workers or 4 pre wintering gynes b. 350mL glass vial c. Stressed or Injured d. Red SPME Fiber : 40 minutes Second Experiment : composition of the volatile molecules produced by stressed individuals Fiber x8 x4
- 15. 13 COMPOUNDS GROUP one • Gynes & Workers 36 % of the total blend • Workers and Gynes : NS • FH and SH : NS • 4,8 DiMe-7-nonen-2-one PCA of the PDMS-SPME analysis of workers and gynes that were stressed (SH, G n=4; W n=8) or frightened (FH, G n=4; W n=8). The ellipses indicate the 95% confidence limit of the data. Second Experiment : composition of the volatile molecules produced by stressed individuals RESULTS
- 16. CONCLUSIONS Marked separation among foundresses, queens and pre wintering gynes. ➢ This result indicates that the chemical signature of a female’s venom gland changes across life- history stages Gynes’ profiles are closer to workers ➢ Gynes’ profiles later shift. Contrary to previous studies, the major compound observed, in this study, in all castes, was 4,8-diMe-7-nonen-2-one (21–28 %) No difference in Workers & Gynes’ profiles – A live individuals (SPME) ➢ No difference in SH &FH’ profiles ➢ 10 news molecules described
- 17. Somes molecules will be tested on bees. Bees may detect some components in hornet alarm pheromone and thus modified their behavior FIELD TRIALS Cheng et al. 2017 Thiery et al. 2018 Berville et al. 2023 PHEROMONE IDENTIFICATION IDENTIFING THE LAST MAJOR MOLECULE Assess the potential effect of each major molecule. One by one, and as a blend PROSPECTS PHEROMONE-BASED TRAP OR REPELLENT PHEROMONE TRIALS (lab)
- 18. Merci