Ortlepp Christine, Gosline John M
Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver BC, Canada V6T 1Z4.
J Exp Biol. 2008 Sep;211(Pt 17):2832-40. doi: 10.1242/jeb.014191.
This study documents the effect of body mass on the size and strength of draglines produced by the orb-weaving spider Araneus diadematus and the jumping spider Salticus scenicus. Silk samples obtained from individuals spanning the range from first-instar juveniles to gravid adults were tested to determine both the properties of the silk material and the strength and static safety factor of the draglines produced by each individual spider. Analysis of material properties indicates that the tensile strength and extensibility of the silks employed by each species are identical over the entire size range of the species. Analysis of the breaking forces for individual draglines, however, indicates that the draglines scale allometrically with the spider's body mass. For Araneus, breaking force (N) scales with body mass (kg) as Fmax=11.2M0.786, and the static safety factor (S(BW)=Fmax/Mg) scales as S(BW)=1.14M(-0.214). For Salticus, Fmax=0.363M0.66 and S(BW)=0.037M(-0.34). Thus, static safety factors decrease as these spiders grow, with values falling to 4-6 for adult Araneus and to 1-2 for adult Salticus. Analysis of these results suggests that the safety lines produced by these two species are not able to absorb the impact energy of most falls with a fixed length of pre-existing silk, except in the smallest of the Araneus spiders. It is therefore likely that both spiders must draw new silk from their spinnerets during falls to keep the dynamic loads on their safety-lines below failure levels.
本研究记录了体重对圆蛛科蜘蛛十字园蛛和跳蛛孔雀跳蛛所产生的拖丝的大小和强度的影响。从一龄幼虫到妊娠成虫范围内的个体获取丝样本进行测试，以确定丝材料的特性以及每只蜘蛛所产生的拖丝的强度和静态安全系数。材料特性分析表明，每个物种所使用的丝的拉伸强度和延展性在该物种的整个大小范围内是相同的。然而，对单个拖丝的断裂力分析表明，拖丝与蜘蛛的体重呈异速生长关系。对于十字园蛛，断裂力（N）与体重（kg）的关系为Fmax = 11.2M^0.786，静态安全系数（S(BW)=Fmax/Mg）的关系为S(BW)=1.14M^(-0.214)。对于孔雀跳蛛，Fmax = 0.363M^0.66，S(BW)=0.037M^(-0.34)。因此，随着这些蜘蛛的生长，静态安全系数会降低，成年十字园蛛的值降至4 - 6，成年孔雀跳蛛的值降至1 - 2。对这些结果的分析表明，除了最小的十字园蛛外，这两个物种所产生的安全线无法利用预先存在的固定长度的丝吸收大多数坠落的冲击能量。因此，很可能这两种蜘蛛在坠落过程中都必须从纺丝器抽出新丝，以使安全线上的动态负荷低于失效水平。
