Development of stem galls induced byDiplolepis triforma(Hymenoptera: Cynipidae) onRosa acicularis(Rosaceae)

Abstract

The cynipid Diplolepis triforma Shorthouse and Ritchie induces a fusiform, multichambered stem gall from leaf buds on Rosa acicularis Lindl. in central and western Canada. Galls at all stages of development were fixed and sectioned using botanical histological techniques to illustrate, for the first time, the unique host-modifying abilities of gall-inducing cynipids that distinguish them from other phytophagous insects. Key events in gall ontogeny, whereby D. triforma gains control and redirects the development of attacked host tissues to provide larvae with shelter and food, include proliferation of cytoplasmically dense parenchymatous cells within the strands of the procambium at the point of egg contact, appearance of nutritive cells when larvae first begin to feed, formation of new xylem and phloem extending from unaffected vascular bundles to the larval chambers, formation of several layers of nutritive cells during the period of larval feeding, and formation of sclerenchyma cells around each larval chamber. The role of these tissues in galler biology is explained.

Developmental morphology of bud galls induced on the vegetative meristems of Quercus castanea by Amphibolips michoacaensis (Hymenoptera: Cynipidae).

“…The present study shows that the structure of gall induced by Amphibolips michoacaensis in different stages of growth is similar to galls induced by others Cynipidae such as hypertrophied nucleus and nucleolus and abundance of ribosomes in nutritive cells (Rothfritsch, 1974;Bronner, 1992;LeBlanc and Lacroix, 2001;Leggo and Shorthouse, 2006). Bronner (1992) reported numerous plastids and mitochondrias in the nutritive cells of the Cynipidae galls, whereas in the galls induced by Amphibolips michoacaensis both mitochondria and chloroplasts occurred in epidermal cells of galls during early stages of growth.…”

“…The larvae of gall-inducing Cynipidae can alter the physiology of host tissues (Leggo and Shorthouse, 2006), the structure and anatomy of layers of gall is related with the stage of development of insect inside of this structure. The changes in the nutritive, spongy and epidermal cells show the specifi c requirements of insect in growth and metamorphosis.…”

“…The majority of the few studies about Cynipidae galls have been made in roses (LeBlanc and Lacroix, 2001;Leggo and Shorthouse, 2006), and one or two about the internal structure of galls induced by cynipid on Quercus; the knopper galls on acorns of Q. robur induced by Andricus quercuscalicis and "Oak Apple Gall" in buds of the English oak Q. robur by Biorhiza pallida (Harper et al, 2004).…”

Galls induced by cynipid wasps of the genus Diplolepis (Hymenoptera: Cynipidae) on the roses of Canada's grasslands

“…Whereas other insects feeding on the surface of leaves or stems have to contend with gusts of drying winds, Diplolepis larvae find themselves in chambers with high humidity. Vascular bundles within tissues of galls are joined to those of the host plant and serve as pipelines bringing water to cynipid larvae (Leggo and Shorthouse 2006). Gall cells, besides providing Diplolepis with food, encase the inducers within a sturdy structure that prevents them from falling off their host plants or being attacked by generalist predators.…”

“…Proliferation of gall cells begins before the eggs hatch. Once the larvae start feeding, they are quickly surrounded by gall cells (Leggo and Shorthouse 2006;Sliva and Shorthouse 2006). As is the case with all cynipids, galls of Diplolepis undergo three phases of development known as initiation, growth, and maturation (Rohfritsch 1992;Brooks and Shorthouse 1998;Sliva and Shorthouse 2006).…”