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

Lepore E, Marchioro A, Isaia M, Buehler MJ, Pugno NM - PLoS ONE (2012)

Bottom Line: Meta menardi has recently been chosen as the "European spider of the year 2012", from the European Society of Arachnology.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.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).

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Bio-inspired Nanomechanics Giuseppe Maria Pugno, Department of Structural Engineering, Politecnico di Torino, Torino, Italy.

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).

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The maximum toughness of different types of (mainly spider) silks.
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pone-0030500-g009: The maximum toughness of different types of (mainly spider) silks.

Mentions: In Figures 9,10,11, we report toughness, ultimate stress and ultimate strain respectively for different types of spider silks; specifically in Figure 11 our record of ultimate strain clearly emerges. The reason for this very high strain is yet unknown but could be caused by an interaction and different disposition of the α-chains and β-pleated sheets within the fibers thus giving them the possibility to stretch to such high strain values. As stated in the introduction, it has been observed that physical interactions between the fibers could influence the elongation data and so increased the stretching capabilities of the stalk, compared to that of the single fiber [34]. We saw that the extreme strain of the stalkscould be caused by a macroscopic unraveling of the stalkitself. The failure strains of the egg sac silk of Araneus diadematus reached values of 30–40%, much lower than our strains [24]. Egg sac threads from Nephila clavipes extended 24±2% their initial length and the maximum stress was 1.3±0.2 GPa whereas for Araneus gemmoides these values were respectively 19±2% and 2.3±0.2 GPa [34].


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

Lepore E, Marchioro A, Isaia M, Buehler MJ, Pugno NM - PLoS ONE (2012)

The maximum toughness of different types of (mainly spider) silks.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3275603&req=5

pone-0030500-g009: The maximum toughness of different types of (mainly spider) silks.
Mentions: In Figures 9,10,11, we report toughness, ultimate stress and ultimate strain respectively for different types of spider silks; specifically in Figure 11 our record of ultimate strain clearly emerges. The reason for this very high strain is yet unknown but could be caused by an interaction and different disposition of the α-chains and β-pleated sheets within the fibers thus giving them the possibility to stretch to such high strain values. As stated in the introduction, it has been observed that physical interactions between the fibers could influence the elongation data and so increased the stretching capabilities of the stalk, compared to that of the single fiber [34]. We saw that the extreme strain of the stalkscould be caused by a macroscopic unraveling of the stalkitself. The failure strains of the egg sac silk of Araneus diadematus reached values of 30–40%, much lower than our strains [24]. Egg sac threads from Nephila clavipes extended 24±2% their initial length and the maximum stress was 1.3±0.2 GPa whereas for Araneus gemmoides these values were respectively 19±2% and 2.3±0.2 GPa [34].

Bottom Line: Meta menardi has recently been chosen as the "European spider of the year 2012", from the European Society of Arachnology.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.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).

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Bio-inspired Nanomechanics Giuseppe Maria Pugno, Department of Structural Engineering, Politecnico di Torino, Torino, Italy.

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).

Show MeSH
Related in: MedlinePlus