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Adhesive properties of tentacles of the protocarnivorous plant Roridula gorgonias and the mechanism of adhesion prevention in the mutualistic mirid bug Pameridea roridulae
Dagmar Voigt
Last modified: 2009-06-25
Abstract
Dagmar Voigt1 and Stanislav Gorb1,2
1 Evolutionary Biomaterials Group, Department of Thin Films and Biological Systems,
Max-Planck Institute for Metals Research, Heisenbergstrasse 03, 70569 Stuttgart, Germany.
2 Department of Functional Morphology and Biomechanics, Zoological Institute of the University of Kiel, Am Botanischen Garten 1-9, 24098 Kiel, Germany.
The three-dimensional trap of the plant Roridula gorgonias Planch. (Roridulaceae) consists of several functional units of various levels. It's glandular trichomes release adhesive, visco-elastic, resinous secretion that traps variety of insects including those having a considerable body mass. In spite of such an elaborate trapping system of the plant, specialized mutualistic mirid bugs Pameridea roridulae Reut. (Heteroptera, Miridae) live on this sticky plant surface an feed on glued insects without being trapped by plant.
In this study we have analyzed (1) the role of different trichome types of R. gorgonias in insect trapping mechanism, and (2) the mechanism responsible for the non-sticky properties of the bug cuticle. We have visualized intact plant surfaces and insect cuticle using Cryo-SEM and measured adhesive properties of plant secretion in contact with different surfaces. Additionally, in a separate experiment we have estimated the stiffness of three different trichome types of the plant trap. A combination of structural and experimental results let us suggest that various trichome types with their different dimensions, stiffness and adhesive properties fulfil different functions in a complex trapping mechanism.
SEM study of cryo-fractures of the fresh cuticle of flies, representing typical prey of R. gorgonias, and P. roridulae bugs, has revealed a thin, fragmentary layer of epicuticular grease in flies. This result led us suggest that the plant adhesive may form proper contact with solid islands of the fly cuticle free of epicuticular grease. On the contrary, a thick and cohesively weak epicuticular greasy film in bugs acts as a sloughing off layer preventing contact formation between sticky plant secretion and solid insect cuticle.
1 Evolutionary Biomaterials Group, Department of Thin Films and Biological Systems,
Max-Planck Institute for Metals Research, Heisenbergstrasse 03, 70569 Stuttgart, Germany.
2 Department of Functional Morphology and Biomechanics, Zoological Institute of the University of Kiel, Am Botanischen Garten 1-9, 24098 Kiel, Germany.
The three-dimensional trap of the plant Roridula gorgonias Planch. (Roridulaceae) consists of several functional units of various levels. It's glandular trichomes release adhesive, visco-elastic, resinous secretion that traps variety of insects including those having a considerable body mass. In spite of such an elaborate trapping system of the plant, specialized mutualistic mirid bugs Pameridea roridulae Reut. (Heteroptera, Miridae) live on this sticky plant surface an feed on glued insects without being trapped by plant.
In this study we have analyzed (1) the role of different trichome types of R. gorgonias in insect trapping mechanism, and (2) the mechanism responsible for the non-sticky properties of the bug cuticle. We have visualized intact plant surfaces and insect cuticle using Cryo-SEM and measured adhesive properties of plant secretion in contact with different surfaces. Additionally, in a separate experiment we have estimated the stiffness of three different trichome types of the plant trap. A combination of structural and experimental results let us suggest that various trichome types with their different dimensions, stiffness and adhesive properties fulfil different functions in a complex trapping mechanism.
SEM study of cryo-fractures of the fresh cuticle of flies, representing typical prey of R. gorgonias, and P. roridulae bugs, has revealed a thin, fragmentary layer of epicuticular grease in flies. This result led us suggest that the plant adhesive may form proper contact with solid islands of the fly cuticle free of epicuticular grease. On the contrary, a thick and cohesively weak epicuticular greasy film in bugs acts as a sloughing off layer preventing contact formation between sticky plant secretion and solid insect cuticle.