Abstract：
Although descended from orb weavers, spiders in the family Theridiidae spin cobwebs whose sticky prey capture gumfoot lines extend from a silk tangle to a surface below. When a crawling insect contacts glue droplets at the bottom of a gumfoot line, the line\'s weak pyriform anchor releases, causing the taut line to contract, pulling the insect from the surface and making its struggles to escape ineffective. To determine if this change in prey capture biomechanics was accompanied by a change in the material properties of theridiid glue, we characterized the elastic modulus and toughness of the glue droplet proteins of four theridiid species at 20-90 % relative humidity and compared their properties with those of 13 orb weaving species in the families Tetragnathidae and Araneidae. Compared to orb weavers, theridiid glue proteins had low extensions per protein volume and low elastic modulus and toughness values. These differences are likely explained by the loss of tension on a gumfoot line when its anchor fails, which may prioritize glue droplet adhesion rather than extension. Similarities in theridiid glue droplet properties did not reflect these species\' evolutionary relationships. Instead, they appear associated with differences in web architecture. Two species that had stiffer gumfoot support lines and longer and more closely spaced gumfoot lines also had stiffer glue proteins. These lines may store more energy, and, when their anchors release, require stiffer glue to resist the more forceful upward thrust of a prey. STATEMENT OF SIGNIFICANCE: When a crawling insect contacts glue droplets on a theridiid cobweb\'s gumfoot line, this taut line\'s anchor fails and the insect is hoisted upward, rendering its struggles to escape ineffective. This strategy contrasts with that of orb weaving ancestors, which rely on more closely spaced prey capture threads to intercept and retain flying insects. A comparison of the elastic modulus and toughness of gumfoot and orb web glue proteins shows that this change in prey capture biomechanics is associated with reductions in the stiffness and toughness of cobweb glue. Unlike orb web capture threads, whose droplets extend in a coordinated fashion to sum adhesive forces, gumfoot lines become untethered, which prioritizes glue droplet adhesive contact over glue droplet extension.
摘要：
虽然来自球体织布工，Theridiidae家族中的蜘蛛旋转蜘蛛网，其粘性猎物捕获gumfoot线从丝绸缠结延伸到下面的表面。当爬行的昆虫接触到脚掌线底部的胶滴时，线的弱梨形锚释放，导致拉紧的线收缩，将昆虫从表面拉出，使其逃脱的斗争无效。为了确定猎物捕获生物力学的这种变化是否伴随着热液胶材料特性的变化，我们在20％-90％的相对湿度下表征了四种热合物种的胶滴蛋白的弹性模量和韧性，并将其特性与Tetragnathidae和Araneidae中的13种球体编织物种的特性进行了比较。与球体编织者相比，热液胶蛋白的每蛋白质体积延伸量低，弹性模量和韧性值低。这些差异很可能是由于当锚索失效时，脚掌线上的张力丧失，这可能优先考虑胶水液滴粘附而不是延伸。热胶滴特性的相似性并不能反映这些物种的进化关系。相反，它们似乎与Web体系结构的差异有关。具有更硬的牙龈支撑线和更长，更紧密间隔的牙龈线的两个物种也具有更硬的胶蛋白。这些线可以储存更多的能量，and,当他们的锚释放时，需要更硬的胶水来抵抗猎物更有力的向上推力。重要声明：当爬行的昆虫接触热蜘蛛网的gumfoot线上的胶滴时，这条拉紧线的锚失效，昆虫被向上吊起，使其逃避的斗争无效。这种策略与球体编织祖先的策略形成鲜明对比，依靠更紧密间隔的猎物捕获线来拦截和保留飞行昆虫。对gumfoot和orb网胶蛋白的弹性模量和韧性的比较表明，猎物捕获生物力学的这种变化与网胶的刚度和韧性降低有关。与orbWeb捕获线程不同，其液滴以协调的方式延伸以总和粘附力，gumfoot线变得不受限制，它优先考虑胶滴粘合剂接触而不是胶滴延伸。
