Sarah Stellwagen: The Biomechanics of Spider Glue
She and colleague Rebecca Rensberg sequenced the genes that encode for the spider glue protein. Their work appears in the April edition of the journal G3-Genes Genomes Genetics.
Stellwagen said she is particularly interested in the "biomechanical properties and genetics of silk, particularly the aggregate glue that orb-weaving spiders deposit on the capture spiral silk of their webs."
"I'll be talking about the biomechanics of spider glue--how droplets of glue on a spiders web stretch, and how environmental variables like humidity, temperature, and ultraviolet light affect that stretch," Stellwagen said. "I'll also be talking about the molecular biology of the glue--discovering the DNA sequences that code for main proteins that make up the glue, and how that sequence relates to the mechanical properties."
Stellwagen said that "most people are unaware of the glue on a spider's web because you can't see the droplets with your naked eye, but it's a really important feature of the web that spiders rely on to capture prey. Spider glue is also a modified silk protein, but has lost its fibrous characteristics that we think of when we hear the word silk. Currently, there are only around 20 full-length silk genes known--but many, many partial sequences--because these genes are really hard to sequence due to their size and repetitiveness. I'll talk about why it's so difficult to sequence silk genes, and what got my research over the hurdles."
An individual orb weaving spider can spin up to seven different types of silk, cach with unique functions and material properties, Stellwagen explained. "The capture spiral silk of classic two-dimensional aéenal orb webs is coated with amorphous glue droplets that function to retain prey that get caught in a web. The glue differs from solid silk fibers as it is a viscoelastic, amorphic, wet material that is responsive to environmental conditions. Humidity causes changes in the glue's maternal properties, like stretchiness and adhesion, while temperature mediates these affects. The glue is more or less resistant to damage caused by ultraviolet radiation depending on a species' habitat."
"At the molecular level, spider glue is a modified silk that is mostly comprised of proteins called spidroins (spider fibroins) encoded by two members of the silk gene family."
Stellwagen, whose postdoctoral research focuses on arachnids, is currently working with Mercedes Burns studying population genetics of Japanese facultative parthenogenic harvestmen. Using Oxford Nanopore, she is sequencing the genome of the polyploid species Leiobunum manubriatum in an effort to understand their mixed ploidy and sexual/asexual reproductive modes.
Stellwagen received her doctorate in biological sciences in July of 2015 from Virginia Polytechnic Institute and State University, Blacksburg, Va. Her dissertation: "Structure and Function of the Viscous Capture Spiral and its Relationship to the Architecture of Spider Orb Webs." She holds two degrees from Clemson University, South Carolina: a bachelor's degree and a master's degree. Her master's thesis: "Spider (Aranea) Diversity, Habitat Distributions and Pitfall Trapping in Kings Mountain National Military Park, South Carolina."
Stellwagen has also published her work on spider glue in the Journal of Experimental Biology and the Journal of Arachnology. She delivered oral presentations on "Towards Spider Glue: Sequencing the Longest Known Silk Family Gene" at the 2019 International Congress of of Arachnology, Christchurch, New Zealand, and the 2018 American Arachnological Society Annual Meeting in Ypsilanti, Mich.
Seminar hosts are Hanna Kahl, UC Davis doctoral student in entomology, and Jason Bond, the Evert and Marion Schlinger Endowed Chair in Insect Systematics, UC Davis Department of Entomology and Nematology.
The seminars, coordinated by medical entomologist/assistant professor Geoffrey Attardo, take place at 4:10 p.m. every Wednesday in Room 122 of Briggs Hall, through June 5. (See list of seminars)
Resources:
Sarah Stellwagen's website