Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2012;7(2):e30500.
doi: 10.1371/journal.pone.0030500. Epub 2012 Feb 8.

Evidence of the most stretchable egg sac silk stalk, of the European spider of the year Meta menardi

Emiliano Lepore  1 , Andrea Marchioro, Marco Isaia, Markus J Buehler, Nicola M Pugno
Affiliations

Evidence of the most stretchable egg sac silk stalk, of the European spider of the year Meta menardi

Emiliano Lepore et al. PLoS One. 2012.

Abstract

Spider silks display generally strong mechanical properties, even if differences between species and within the same species can be observed. While many different types of silks have been tested, the mechanical properties of stalks of silk taken from the egg sac of the cave spider Meta menardi have not yet been analyzed. Meta menardi has recently been chosen as the "European spider of the year 2012", from the European Society of Arachnology. Here we report a study where silk stalks were collected directly from several caves in the north-west of Italy. Field emission scanning electron microscope (FESEM) images showed that stalks are made up of a large number of threads, each of them with diameter of 6.03 ± 0.58 µm. The stalks were strained at the constant rate of 2 mm/min, using a tensile testing machine. The observed maximum stress, strain and toughness modulus, defined as the area under the stress-strain curve, are 0.64 GPa, 751% and 130.7 MJ/m(3), respectively. To the best of our knowledge, such an observed huge elongation has never been reported for egg sac silk stalks and suggests a huge unrolling microscopic mechanism of the macroscopic stalk that, as a continuation of the protective egg sac, is expected to be composed by fibres very densely and randomly packed. The Weibull statistics was used to analyze the results from mechanical testing, and an average value of Weibull modulus (m) is deduced to be in the range of 1.5-1.8 with a Weibull scale parameter (σ(0)) in the range of 0.33-0.41 GPa, showing a high coefficient of correlation (R(2) = 0.97).

PubMed Disclaimer

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. FESEM image of the spinnerets of Meta menardi (1. Anterior lateral; 2. Posterior median; 3. Posterior lateral).
Figure 2
Figure 2. Egg sac of the spider Meta menardi.
Photo by Francesco Tomasinelli (2009).
Figure 3
Figure 3. Distinction of the stalk types: cable-like (Group A) (a) and ropey-like (Group B) (b).
Figure 4
Figure 4. FESEM characterization of the silk stalk at different magnifications.
Figure 5
Figure 5. Stress - strain curves of group A (a) or B (b) stalks.
Figure 6
Figure 6. Weibull statistics for stress of group A (a) or B (b) stalks.
Figure 7
Figure 7. Detailed views of fracture surfaces of broken silk fibers.
Figure 8
Figure 8. FESEM characterization of the stalk cut with FIB: (a, b, c) at an eye angle of 52°, (d) from the top.
Figure 9
Figure 9. The maximum toughness of different types of (mainly spider) silks.
Figure 10
Figure 10. The maximum strength of different types of (mainly spider) silks.
Figure 11
Figure 11. The maximum strain of different types of (mainly spider) silks, showing the record for egg sac silk stalks observed in our experiments.
See this image and copyright information in PMC

References

    1. Brunetta L, Craig CL. Spider Silk, Evolution and 400 Million Years of Spinning, Waiting, Snagging, and Mating. Csiro Publishing 2010
    1. Keten S, Xu Z, Ihle B, Buelher MJ. Nanoconfinement controls stiffness, strength and mechanical toughness of β-sheet crystals in silk. Nature Materials. 2010;9:359–367. - PubMed
    1. Blackledge TA, Hayashi CY. Silken toolkits: biomechanics of silk fibers spun by the orb web spider Argiope argentata (Fabricius 1775). J Exp Biol. 2006;209:2452–2461. - PubMed
    1. Blackledge TA, Kuntner M, Agnarsson I. The Form and Function of Spider Orb Webs: Evolution from Silk to Ecosystems. Burlington: Academic Press. Advances in Insect Physiology. 2011;41:175–262.
    1. Rousseau ME, Lefevre T, Pezolet M. Conformation and orientation of proteins in various types of silk fibers produced by Nephila clavipes Spiders. Biomacromolecules. 2009;10:2945–2953. - PubMed

Publication types