Structure and mechanical strength of larval cuticle of sawflies capable of “easy bleeding” a defence strategy against predators evolved in Tenthredinidae (Hymenoptera)

The cuticle of Tenthredinidae (Hymenoptera) larvae is ruptured after a very mild mechanical stress and hemolymph is released. This phenomenon, called “easy bleeding” is considered as a defence strategy against predators. We investigated the cuticle structure of some selected species capable of “easy...

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Bibliographic Details
Published in:Tissue & cell 2005-02, Vol.37 (1), p.67-74
Main Authors: Burret, Michael, Boevé, Jean-Luc, Barker, Alison, Spindler-Barth, Margarethe
Format: Article
Language:English
Subjects:
Animals
Athalia rosae
Chitin
Cuticle strength
Hemolymph
Hemolymph - secretion
Hymenoptera - anatomy & histology
Hymenoptera - physiology
Larva - physiology
Larva - ultrastructure
Microscopy
Microscopy, Electron, Scanning
Microscopy, Electron, Transmission
Sawfly
Tenthredinidae
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Summary:The cuticle of Tenthredinidae (Hymenoptera) larvae is ruptured after a very mild mechanical stress and hemolymph is released. This phenomenon, called “easy bleeding” is considered as a defence strategy against predators. We investigated the cuticle structure of some selected species capable of “easy bleeding” by light-, transmission- and scanning microscopy and compared it with phylogenetically-related sawfly species without this defense strategy (control). Cuticle thickness has no major influence on mechanical stability, but pronounced local differences in thickness seem to be inversely correlated with mechanical strength. The density of chitin fibrils is considerably reduced in animals capable of easy bleeding and the fibres form a loose 3D network in contrast to the densely packed layers seen in related “non easy bleeding” species like Strongylogaster multifasciata, where a pressure of 2584 kPa is needed to pierce the integument , and which served as a control. Efficient bleeders like Phymatocera aterrima (203 kPa) and Rhadinoceraea nodicornis (219 kPa) are devoid of any defined layers or other structural elements. In Athalia rosae (Allantinae) (539 kPa), and Aglaostigma discolor (Tenthredininae) (1494 kPa) – bleeders with medium efficiency – a reduced number of layers are observed by LM and TEM and a loose network of chitin fibres is visible after treatment with KOH.
ISSN:0040-8166
1532-3072
DOI:10.1016/j.tice.2004.10.005