Collaborative Research: Behavior and Evolution of the Novel Self-Curing Bioadhesive of Moth-Specialist Spiders

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Adhesives produced by animals and plants provide novel materials for engineering and consumer applications. How these organisms produce and use their biological adhesives is the key to understanding how they function mechanically and how they have evolved. An extraordinary glue -- with an unusual combination of water-like fluidity when applied and rubbery toughness when set -- is produced by a small group of spiders. This glue is predicted to be critical to how these spiders catch flying moths, which few other spiders can do. In this research, the function and genetics of glues in moth-catchers will be compared to those in glues of spiders that don’t catch moths. The glues’ strength and toughness will be measured in the field and in the lab using a purpose-built testing machine. The location and sequence of glue genes, and the tissues where these genes are activated, will be uncovered. A new computer model will explain how the glue changes from a flowing liquid to a tough adhesive in seconds, and how this allows the glue to stick to moth scales. This research will be conducted, in part, by undergraduates and high school students carrying out one- and two-year apprenticeships mentored by the investigators to provide training for STEM careers. The team’s integrated research efforts will lay groundwork for advancing development of engineered adhesives from naturally produced materials with novel mechanical properties. A comprehensive understanding of a biomaterial should include its mechanical behavior in its organismal, ecological, and evolutionary context. Bioadhesives, such as the glues produced by spiders, are excellent systems for this type of investigation because their mechanical behavior is directly observable in the organism's ecological context. For most orb-weaving spiders, one type of abundant prey is elusive: moths. But moths are captured by cyrtarachnine spiders. They use a capture glue that possesses low viscosity and when in contact with moths has the highest adhesive strength and toughness among spider glues measured among spider glues. This project tests the hypothesis that this capture glue is the key adaptation of the Cyrtarachninae for catching moths. The glue’s rate and extent of spreading will be measured with high-speed micro-videography to test competing microfluidic models. Adhesive behavior of the glue, the second step in the capture process, quantified as adhesive strength (N) and adhesive toughness (Nm-2), will be measured in the field and in the lab using pull-off tension tests. Genes for the glue proteins will be identified using a combination of genomic, transcriptomic, and proteomic approaches. Finally, genomic and mechanical traits will be mapped onto the phylogeny of the Cyrtarachninae and the states of the hypothetical common ancestor reconstructed. Because early and sustained research fosters retention and commitment of students in STEM careers, in each stage of this research, high school and college students will become long-term apprentices, participating for one or two years of intensive research training under direct supervision of the investigators.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.