Anatomy and Ultrastructure of Galls Induced by Neuroterus quercusbaccarum (Hymenoptera: Cynipidae) on Oak Leaves (Quercus robur)

Abstract

The structure and ultrastructure of two developmental stages of the spangle gall induced by Neuroterus quercusbaccarum (Hymenoptera, Cynipidae) were investigated using light microscopy (LM), fluorescence microscopy (FM), and transmission (TEM) and scanning (SEM) electron microscopy. The general design of the gall structure was typical of Cynipidae, but some structural features distinguished the spangle gall. Previously undescribed, characteristic multicellular epidermal protuberances with large openings were observed in autumn on the surface of galls. These may facilitate the gas exchange between the atmosphere and the inside of the gall, thus assisting larval respiration. The larval chamber is surrounded by both a sclerenchymatous capsule and numerous cells containing calcium oxalate crystals that may both serve as protective barriers. In young galls, the nutritive tissue is a wall-less protoplasmic mass, potentially easily accessible to young larvae with delicate mandibles. Cell walls only develop at a later stage. The nutritive tissue was found to be rich in proteins and lipids, but starch grains were not observed. Cellular topology suggests that spangle galls grow by anticlinal division of marginal epidermal cells and periclinal division of subepidermal cells. Cellular proliferation (hyperplasia) also occurs in the leaf tissue near the connection with the gall peduncle, which eventually lignifies.

Comparative transcriptome reprogramming in oak galls containing asexual or sexual generations of gall wasps

“…The CT imaging also revealed the small size of the attachment, approximately 0.2 mm, and showed the previously described calcium oxalate layer surrounding the larval growth chamber (Jankiewicz et al, 2021). The CT imaging shows the density differences of the internal structures of the gall and enables a 3D image of the entire gall structure to be built.…”

“…The CT imaging shows the density differences of the internal structures of the gall and enables a 3D image of the entire gall structure to be built. This approach provides a different prospective to the scanning electron images of these two galls currently published (Jankiewicz et al, 2017, Jankiewicz et al, 2021).…”

“…CT imaging revealed other features, such as the attachment between the leaf and the gall is approximately 0.2mm in diameter. Additionally, a lighter line can be seen in the centre of both galls which is likely to be calcium oxalate crystals, a defence mechanism of the gall (Jankiewicz et al, 2021).…”

Cynipid wasps systematically reprogram host metabolism and restructure cell walls in developing galls

“…Despite the central role cell walls play in determining the structure and function of plant tissues, little is known about how plant cell walls are modified during the development of insect galls. Previous qualitative studies have shown changes in lignin (Tanaka et al, 2013), tannins (Jankiewicz et al, 2021), and several polysaccharides (Formiga et al, 2013;…”

Integrated Transcriptome and Metabolome Dynamic Analysis of Galls Induced by the Gall Mite Aceria pallida on Lycium barbarum Reveals the Molecular Mechanism Underlying Gall Formation and Development

“…Moreover, these dramatic modifications of host plants caused by gall inducers are usually accompanied by extensive reprogramming of plant gene expression [ 24 ]. Specifically, the expression modification of these genes affects the plant’s defense responses [ 25 , 26 ], hormone pathways [ 27 , 28 ], cell cycle, cell wall and cytoskeleton organization [ 29 , 30 ], developmental processes [ 31 , 32 ] and metabolic reprogramming [ 19 , 33 ]. Transcriptomic and metabolomic approaches can provide deep insights into the complexity of gall inducer–host plant interactions and offer reliable, multidimensional molecular biology information for studying and controlling gall inducers [ 17 , 27 , 34 ].…”