Spider’s Adhesion (SpiA) Characterization of the ecological nische of cribellate and ecribellate spiders as function of the functionality and evolution of their capture threads

• Applicant: Dr. Anna-Christin Joel
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions ; Animal Physiology and Biochemistry ; Biomaterials
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 406021806

Spiders are important predators and inhabit most ecological niches of the earth. The latest extrapolation estimated a prey consumption of the complete spider society of 400 to 800 million tons per year. Over 90% of this prey are insects. Hence, a distribution of insects, like in the late Cretaceous, leads to a diversification of spiders as well. Likewise, this long lasting evolutionary arm race led probably to the high diversity of spiders and insects of today. This diversity is also reflected in the tactics used by spiders to capture prey. For example, Araneoidae cover their capture threads with glue droplets, whereas the polyphyletic cribellate spiders use nanofibres as capture threads. It is suggested that the cribellate capture threads are more primitive and gluey capture threads evolved from this ancestor. Besides this hypothesis, it is still not known what triggered the evolution of the gluey capture threads in the first place and what ecological benefits let both capture thread types coexist nowadays. Most studies trying to link climatic conditions to the adhesive strength of the different capture threads have till now ignored any biotic interaction, occurring between the surface of insect prey and the capture threads. A recent study, however, has proven that cribellate spiders in fact make use of a viscid waxy layer covering all insects. This layer consist of cuticular hydrocarbons and serve as a protection against desiccation and furthermore for inter- and intraspecific communication. Cribellate spiders use this layer and embed their nanofibrous capture threads into the viscid cuticle of their prey, thus enhancing adhesion about eight times compared to wax free surfaces.Within this project SpiA, I want to study how the cuticular hydrocarbon composition as well as the cuticle morphology influences the adhesion of different capture threads (biotic interaction). Furthermore, I want to study whether different climatic conditions influences this interaction. The results of the laboratory experiments will be corroborated by determining the climatic optimum of the used spiders, as well as modelling the climatic niche of spiders with different capture threads. Finally a survey in nature will determine whether the different capture threads are diversified to different climatic niches. SpiA will thus enable me to answer the question what ecological benefit enables the coexistence of different capture thread types nowadays and whether an evolutionary arm race between insect prey and spiders triggered the development of gluey capture threads.

• DFG Programme: Research Grants