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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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Egg sac of the spider Meta menardi.Photo by Francesco Tomasinelli (2009).
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pone-0030500-g002: Egg sac of the spider Meta menardi.Photo by Francesco Tomasinelli (2009).

Mentions: The cave spider Meta menardi (Latreille) is generally found in dark and humid places like caves and mines, throughout the northern hemisphere; and from northern Europe to Korea and northern Africa [16]. The cave spider Meta menardi has recently been chosen as the “European spider of the year 2012” from the European Society of Arachnology. Since no engineering studies of the egg sac of the cave spider Meta menardi yet exist and just few ones have been focused on egg sacs, we decided to conduct tensile tests on stalks of egg sac silk. We tested the stalk which connect the egg sacs of Meta menardi to the ceiling of the caves (the arrow, in Figure 2, indicates such sample). In total 15 stalks were found and were pulled until they broke. Samples were viewed under FESEM to analyze the fracture surfaces and measure the diameter of the stalk. To be able to see how the threads were stacked in each stalk, a Focused Ion Beam (FIB) was used to cut the stalk. Using the FESEM micrographies of the cross-section of the FIB-cut stalk and the processing software ImageJ 1.41o, we were able to measure the real diameter and the exact number of single threads in each stalk, improving the accurateness [19]. Thus, the stress-strain curves and the Weibull shape and scale parameters of the stalk of the egg sac silk of Meta menardi are here determined.


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)

Egg sac of the spider Meta menardi.Photo by Francesco Tomasinelli (2009).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0030500-g002: Egg sac of the spider Meta menardi.Photo by Francesco Tomasinelli (2009).
Mentions: The cave spider Meta menardi (Latreille) is generally found in dark and humid places like caves and mines, throughout the northern hemisphere; and from northern Europe to Korea and northern Africa [16]. The cave spider Meta menardi has recently been chosen as the “European spider of the year 2012” from the European Society of Arachnology. Since no engineering studies of the egg sac of the cave spider Meta menardi yet exist and just few ones have been focused on egg sacs, we decided to conduct tensile tests on stalks of egg sac silk. We tested the stalk which connect the egg sacs of Meta menardi to the ceiling of the caves (the arrow, in Figure 2, indicates such sample). In total 15 stalks were found and were pulled until they broke. Samples were viewed under FESEM to analyze the fracture surfaces and measure the diameter of the stalk. To be able to see how the threads were stacked in each stalk, a Focused Ion Beam (FIB) was used to cut the stalk. Using the FESEM micrographies of the cross-section of the FIB-cut stalk and the processing software ImageJ 1.41o, we were able to measure the real diameter and the exact number of single threads in each stalk, improving the accurateness [19]. Thus, the stress-strain curves and the Weibull shape and scale parameters of the stalk of the egg sac silk of Meta menardi are here determined.

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