Meeting Abstract

39.7  Jan. 6  Stretchy, sticky and strong: evolution and ecology of spider capture fibers SWANSON, B.O.*; HAYASHI, C.Y.; Gonzaga University; Univ. of California, Riverside swansonb@gonzaga.edu

Spider silk provides an excellent model for examining connections between the properties of biological materials and organismal ecology. Orb-weaving spiders spin sticky capture threads that are made of exceptionally extensible and strong materials, resulting in tough fibers thought to be adapted for arresting flying insects by dissipating their kinetic energy. Using tensile testing, we ask whether this material is variable across spider species and whether we can discern patterns in the evolution and ecology of spider capture silks. The material properties of the capture spiral vary greatly across species. Extensibility, strength and toughness all differ up to approximately 6-fold across species. These material differences, along with differences in fiber size, dictate that the mechanical performance (energy and force required to break the fiber) of capture threads varies by more than an order of magnitude across species. Material properties can also be evolutionarily correlated. Species with small diameter fibers tend to have tougher materials, suggesting compensation to maximize breaking energy. There is also a negative correlation between strength and extensibility, suggesting a trade-off between these properties. The different properties of these capture silks help define feeding niche by determining the range of prey that can be caught in an orb web.