Extreme acidity in a cynipid gall: a potential new defensive strategy against natural enemies

The morphology of insect-induced galls contributes to defenses of the gall-inducing insect species against its natural enemies. In terms of gall chemistry, the only defensive compounds thus far identified in galls are tannins that accumulate in many galls, preventing damage by herbivores damage of the galls. Intrigued by the fruit-like appearance of the translucent oak gall (TOG; Amphibolips nubilipennis, Cynipidae, Hymenoptera) induced on red oak (Quercus rubra), we found that this gall tastes tart and hypothesized that this gall accumulates acids as a defensive strategy. We found that the pH of the gall is between 2 and 3, making it among the lowest pH levels found in plant tissues. We examined the organic acid content of TOG and compared it to fruits and other galls using high performance liquid chromatography (HPLC) and gas chromatography – mass spectrometry (GC-MS). Malic acid, an acid with particularly high abundance in apples, represents 66% of the organic acid detected in TOGs. The concentration of malic acid was two times higher than in other Amphibolips galls and in apples. Gall histology showed that the acid-containing cells were enlarged and vacuolized just like mesocarp cells found in fruits. Accumulation of organic acid in gall tissues is convergent with fruit morphology and may constitute a new defensive strategy against predators and parasitoids.



Work Title Extreme acidity in a cynipid gall: a potential new defensive strategy against natural enemies
Open Access
  1. Antoine Guiguet
  2. Nathaniel B McCartney
  3. Kadeem J. Gilbert
  4. John Tooker
  5. Andrew Deans
  6. Jared Ali
  7. Heather Hines
  1. Gall
  2. Cynipidae
  3. Insect
  4. Entomology
License In Copyright (Rights Reserved)
Work Type Article
  1. Biology Letters
Publication Date March 1, 2023
  1. Entomology
DOI doi:10.26207/f85j-3a87
Publisher Identifier (DOI)
  1. https://doi.org/10.1098/rsbl.2022.0513
Deposited March 01, 2023




This resource is currently not in any collection.

Work History

Version 1

  • Created
  • Updated
  • Updated
  • Added Creator Andrew Deans
  • Added Creator Heather Hines
  • Added Creator John Tooker
  • Added Creator Jared Ali
  • Added AcidGall_V7.pdf
  • Updated License Show Changes
    • https://rightsstatements.org/page/InC/1.0/
  • Published
  • Updated

Version 2

  • Created
  • Added AcidGall_SubmittedVersion_ Revised.docx
  • Published
  • Updated Keyword, Subject, Publisher Show Changes
    • gall, Cynipidae, insect, entomology
    • Gall, Cynipidae, Insect, Entomology
    • entomology
    • Entomology
    • Biology Letters (The Royal Society)
    • Biology Letters
  • Updated Creator Andrew Deans
  • Updated Creator Heather Hines
  • Updated Creator John Tooker
  • Updated Creator Jared Ali
  • Added Creator Antoine Guiguet
  • Added Creator Nathaniel B McCartney
  • Added Creator Kadeem J. Gilbert
  • Updated

Version 3

  • Created
  • Deleted AcidGall_V7.pdf
  • Published
  • Updated