Spiders that don’t produce high-quality silk can’t eat. The silk that spiders use to make their webs is essential to their survival; however, spiders live in numerous locations that necessitate fine-tuning their webs for local success. The glue that keeps orb-weaver spiders’ webs sticky has been studied by scientists to learn how its material properties change under different conditions.
The study’s co-corresponding author, Dr. Nadia Ayoub of Washington and Lee University, stated, “Determining how material properties evolve opens the doors to the discovery of the sticky protein components of biological glues.” Since proteins, which are encoded by genes, make up the majority of spider silk fibers and glues, they serve as an excellent model for addressing these concerns.”
“Spider silks and glues have enormous biomimetic potential,” added co-corresponding author Dr. Brent Opell of Virginia Tech. Bugs make pastes with noteworthy properties that would have applications in industry, medication, and then some.”
“These proteins’ sequences are also similar across species, but the relative abundance of individual proteins varies.” Modifying protein ratios is most likely a quick way for adjusting biological glue material qualities.”
Dr. Brent Opell of Virginia Tech, co-corresponding author.
Messed up in cobwebs
Each strand of a circle weaver’s cobwebs adds to the catch of food. The prey is entrapped by sticky lines until the spider can tackle it, and the web’s stiff frame absorbs the impact. An aggregate gland-produced aqueous glue gives these lines their stickiness. To get the best stickiness for the local humidity, the glue needs to be optimized because it takes in water from the air. However, because there are numerous species of orb-weaving spiders that inhabit various environments, their glue needs to adjust to various levels of humidity.
Ayoub and her colleagues focused on two species: Argiope argentata, which lives in dry environments, to understand how spider glue adapts, and Argiope trifasciata, a plant that thrives in moist conditions. The researchers used A. argentata spiders to construct webs in the laboratory after collecting webs from A. trifasciata in the wild. The researchers fed the spiders a diet similar to that of their usual prey and compared the glue droplet volume to that of wild controls to ensure that the humidity in the laboratory was not affecting the properties of the droplets. After that, they looked into the glue’s proteins and the properties of the material in the droplets.
A sticky situation
The team discovered that A. argentata spider droplets are smaller than those of A. trifasciata spiders and absorb less water as the humidity in the area rises. Additionally, they absorbed less water from the surrounding air due to their smaller protein cores and smaller volume droplets. The stiffness of the protein core of the glue droplets determines the toughness of the droplets for both spider species; A. argentata’s protein core toughness decreased with increasing humidity. Droplets of A. argentata thread glue were typically closer together and stickier.
The researchers likewise dissected the proteins tracked down in the paste drops to understand how these distinctions in material properties emerge from the proteins. A. argentata glue contained the protein products of four genes that did not appear in A. trifasciata glue, despite the fact that the proteins they discovered were similar but appeared in different proportions. This glue’s increased toughness and decreased capacity for water absorption may be explained by these additional proteins and a more balanced ratio of AgSp1 and AgSp2 proteins.
Opell stated, “The two species share the majority of their protein components despite the dramatic differences in material properties.” Although the relative abundance of each protein varies, the sequences of these proteins are also similar across species. The material properties of biological glues can probably be changed quickly by changing the ratios of proteins.”
“This concentrate just analyzed two species, so our proposed connections among proteins and material properties are restricted,” advised Ayoub. “However, we are currently documenting the material properties and components of proteins from a wide range of species, giving us more power to identify the mechanisms by which proteins generate material properties.”
More information: Orb weaver aggregate glue protein composition as a mechanism for rapid evolution of material properties, Frontiers in Ecology and Evolution (2023). DOI: 10.3389/fevo.2023.1099481
