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- Table 1.
Quasistatic material properties of silk spun by Argiope argentata compared to other araneid spiders
True values Engineering values Silk Young's modulus (GPa) Ultimate strength (MPa) Extensibility (mm/mm) Ultimate strength (MPa) Extensibility (mm/mm) Toughness (J cm-3) Source Major ampullate (N=5, n=135) 8.0±0.8 1495±65 0.205±0.005 1217±56 0.228±0.007 136±7 This study Araneus sericatus (n=15) 8.6±- 880±- 0.22±- 710±- 0.24±- 106±- (Denny, 1976) Araneus diadematus (n=6) 1.2±0.2 1154±14 0.33±0.02 824±10 0.40±0.03 194±- (Köhler and Vollrath, 1995) Araneus gemmoides (n=10) - 4700±500 0.23±0.05 - - - (Stauffer et al., 1994) Argiope trifasciata (n=28) 6.9±0.4 - - 600±50 0.30±0.02 90±10 (Pérez-Rigueiro et al., 2001) Tubuliform (N=4, n=29) 11.6±2.1 476±90 0.2857±0.015 360±70 0.337±0.019 95±17 This study Araneus gemmoides (n=10) - 2300±200 0.19±0.02 - - - (Stauffer et al., 1994) Araneus diadematus (n∼400) 8.7±0.1 - - 270±3 0.32±0.01 - (Van Nimmen et al., 2005) Minor ampullate (N=8, n=51) 10.6±1.2 923±154 0.330±0.033 669±113 0.401±0.047 137±22 This study Argiope trifasciata (n=11) 8.9±0.5 - - 483±34 0.556±0.04 150±12 (Hayashi et al., 2004) Araneus gemmoides (n=10) - 1400±100 0.22±0.07 - - - (Stauffer et al., 1994) Araneus diadematus (n=55) - - - - 0.34±- - (Work, 1977) Aciniform (N=6, n=28) 10.4±1.4 1052±120 0.404±0.024 636±78 0.505±0.039 230±31 This study Argiope trifasciata (n=10) 9.8±1.1 - - 687±56 0.83±0.06 376±39 (Hayashi et al., 2004) Capture spiral (N=5, n=87) 0.001±0.0001 534±40 1.72±0.05 95±9 4.65±0.26 75±6 This study Araneus sericatus (n=41) - 1270±45 1.19±0.05 296±10 3.29±0.32 150±9 (Denny, 1976) Araneus diadematus (n=6) - 1338+80 1.75±0.15 233±14 4.75±0.16 283±18 (Köhler and Vollrath, 1995) -
All values are means ± s.e.m. For data from this study, s.e.m. was calculated using individual spiders (N) as the sampling unit, while values from most of the other studies utilized the total number of fibers tested (n). —, data were not obtained.
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- Fig. 1.
Quasistatic mechanical properties of each type of fibrous silk spun by Argiope argentata (mean ± s.e.m.). Standard errors were calculated using individual spiders, rather than total numbers of fibers tested, as the sampling unit. See Table 1 for sample sizes. ac, aciniform; cp, capture spiral; mj, major ampullate; mn, minor ampullate; tb, tubuliform.
- Table 2.
Dynamic material properties of silk spun by Argiope argentata and the western black widow Latrodectus hesperus
Loss tangent Storage modulus (GPa) Silk Initial Max Final Initial At max. loss tan Final Source Major ampullate (N=4, n=27) 0.077±0.003 0.172±0.009 0.054±0.002 6.2±0.3 7.8±0.2 40.4±0.9 This study Latrodectus hesperus (n=12) 0.063±0.007 0.197±0.009 0.075±0.003 8.7±1.1 10.6±0.8 47.6±3.3 (Blackledge et al., 2005c) Tubuliform (N=1, n=6) 0.031±0.003 0.113±0.010 0.068±0.006 6.5±0.5 7.5±0.7 12.8±1.0 This study Minor ampullate (N=2, n=6) 0.054±0.009 0.160±0.005 0.072±0.001 10.5±0.6 10.0±0.8 48.0±2.2 This study Aciniform (N=1, n=2) 0.043±0.007 0.149±0.021 0.023±0.013 24.6±3.0 24.4±4.1 54.7±0.0 This study Capture spiral (N=1, n=6) — — 0.057±0.011 — — 24.5±1.8 This study -
All values are mean ± s.e.m. For these data only, s.e.m. was calculated using the total number of fibers tested (n) as the sampling unit rather than individual spiders (N). —, data were not obtained.
All silks are from Argiope argentata, except major ampullate silk from Latrodectus hesperus.
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- Fig. 2.
Typical stress–strain curves for each of the five fibrous silks spun by Argiope argentata. Five tests are shown for each silk. Note the difference in the magnitude of the x axis for most types of silk (A–D) relative to capture spiral silk (E).
- Fig. 3.
Diameters of single fibers (mean ± s.e.m.) for each of the different types of silks spun by Argiope argentata. Standard errors were calculated using individual spiders, rather than total numbers of fibers tested, as the sampling unit. See Table 1 for sample sizes. ac, aciniform; cp, capture spiral; mj, major ampullate; mn, minor ampullate; tb, tubuliform.
- Fig. 4.
Dynamic mechanical properties of each type of fibrous silk spun by Argiope argentata (mean ± s.e.m.). For these data only, s.e.m. was calculated using the total number of fibers tested as the sampling unit, rather than individual spiders. Properties for capture spiral were measurable only at high strain. See Table 2 for sample sizes. E′, storage modulus; tanδ , loss tangent; ac, aciniform; cp, capture spiral; mj, major ampullate; mn, minor ampullate; tb, tubuliform.
- Table 3.
Hypothesized relationships between molecular structure, mechanical performance, and ecological use of silks spun by Argiope argentata
Silk Molecular elements Mechanical performance Ecological function Major ampullate Composition: GA and poly(A) motifs, short repeats of GPGXn motifs1,2 High tensile strength, low extensibility, high loss tangent, exhibits super contraction when wetted, higher hysteresis Draglines, primary dry structural elements of most capture webs 2° structure: β-sheet crystals oriented along fiber axis embedded in amorphous matrix3,4 Tubuliform Composition: A and S rich, long and complex repeats lacking in subrepeat motifs5,6 High modulus, low strength, very little stiffening after fiber yield, consistently low storage modulus, loss tangent is relatively constant after fiber yield, thick diameter Inner flocculent silk of egg sacs 2° structure: β-sheets twist parallel to fiber orientation embedded in amorphous matrix3,7,8,9 Minor ampullate Composition: GA motifs lack poly(A) motifs1 High modulus and extensibility, moderate tensile strength and toughness Temporary spiral of orb, sometimes added to draglines 2° structure: β-sheet crystals oriented along fiber axis embedded in amorphous matrix9 Aciniform Composition: G, A and S rich, long, complex repeats lacking in subrepeat motifs10 High modulus, extensibility and toughness, high storage modulus, multi-strand sheet of fine fibers Prey wrapping, stabilimentum web decorations, outer layer of egg sacs 2° structure: uncharacterized Capture spiral Composition: core fiber (flagelliform silk gland) coated with glycoprotenin glue, core fiber has long repeats of GPGXn motifs11 Extremely extensible and resilient, highly compliant, glue-coated wet fiber Sticky spiral of ecribellate orb webs 2° structure: lacks β-sheet, subrepeats fold into molecular `nanosprings', plasticized fiber12,13,14,15, -
Amino acids are indicated by one-letter abbreviations: A, alanine; G, glycine; P, proline; S, serine; X, glycine or other amino acid. 1(Gatesy et al., 2001), 2(Xu and Lewis, 1990), 3(Parkhe et al., 1997), 4(Thiel et al., 1997), 5(Garb and Hayashi, 2005), 6(Tian and Lewis, 2005), 7(Barghout et al., 2001), 8(Barghout et al., 1999), 9(Dicko et al., 2004), 10(Hayashi et al., 2004), 11(Hayashi and Lewis, 2000), 12(Gosline et al., 1984), 13(Hayashi and Lewis, 1998), 14(Hayashi and Lewis, 2001), 15(Vollrath and Edmonds, 1989).
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- Fig. 5.
Exemplar dynamic mechanical curves for each of the five fibrous silks spun by Argiope argentata. Gray denotes the loss tangent (tan δ) and black denotes the storage modulus (E′). Loss tangent could not be measure effectively for capture spiral due to the extremely low magnitude of the loss modulus. Note the difference in the scale of the x axis for capture spiral (E) relative to other types of silk (A–D).
- Fig. 6.
Scanning electron microscope image of a fiber of tubuliform silk exhibiting characteristic grooves and nodules on its exterior. Bar, 5 μm.
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