Oak leaf galls: Neuroterus numismalis and Cynips quercusfolii, their structure and ultrastructure

Leszek Stanisław Jankiewicz,Franciszek Dubert,Barbara Dyki,Aleksandra Machlańska

doi:10.5586/asbp.3537

Abstract

Anatomy and surface ultrastructure of the galls induced on oak leaves by the insects – Neuroterus numismalis (Ol.) and Cynips (Diplolepis) quercusfolii L. – were investigated using a scanning electron microscope (SEM) and a light microscope (LM). The observations in SEM and in LM enabled a detailed description of these galls and comparison of their structure with that of the typical oak leaf. In N. numismalis gall, the external distal tissues were classified as similar to phellem (cork), phellogen, and phelloderm, and a lateral marginal tissue as parenchyma with the likely role of a storage tissue. In the young C. quercusfolii gall, the cells of internal, nutritive tissue, on which the larva is grazing, formed globules rising above the surface of larval chamber. Many of them seemed to be destroyed by the larval action. In the gall which attained half of its final size, the tissues near the larval chamber were already partly lignified. The microorganisms (mainly fungi) which live in the oak phyllosphere, occurred also on the galls. We believe that the deep changes in the morphogenetic program of a leaf, which are caused by the gall-forming insects, are impossible without the transfer and the integration of the insect genetic material with that of the host plant. We also postulate that a larva secrets as yet hypothetical substances, which redirect the nutrients transport from the leaf blade towards the gall and support its vital functions.

Highlights

The morphology and anatomy of plant galls caused by insects were described by several authors [1,2,3,4,5,6,7]
We show the details of the surface ultrastructure and anatomy of oak leaf galls caused by Neuroterus numismalis (Ol.) and Cynips (Diplolepis) quercusfolii L., and compare them to the typical leaf structure of the oak (Quercus robur L.)
To be certain what changes in oak leaf morphogenesis are induced by the gall-forming insect, we first investigated the surface ultrastructure and anatomy of a typical, mature oak leaf

Summary

Introduction

The morphology and anatomy of plant galls caused by insects (zoocecidia) were described by several authors [1,2,3,4,5,6,7]. A very detailed description of the gall of related species N. quercusbaccarum was presented by Hough [8] and investigated from a histological point of view by Kovácsne Koncz et al [9]. The latter authors proved the presence of an increasing gradient of proteins and lipids towards the larval chamber

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