Exiting Preliminary Results

Glue droplets in the capture spirals of the orb-web help in retaining the insect long enough for the spider to reach it.

We can test stickiness of glue in the lab by measuring the force required to peel off the glue from a glass surface (Image 1) and by looking at the chemical composition using Nuclear Magnetic Resonance or NMR (Image 2).

 

Image 1. Experimental setup to measure the force pull-off behavior of glue from a glass surface. Image credit: Matjaž Gregorič

Some factors can affect how sticky this glue is:

1. Amount and types of Glycoproteins in the droplets.

2.Amount and type of Salts.

3. Abiotic factors like humidity and temperature.

Preliminary NMR results for a specie of spider in Hawai'i (Tetragnatha hawaiensis) show qualitative differences in salt peaks for species found in Hawai'i and in Maui (Image 2).

 

Image 2. NMR results for Tetargnatha hawaiensis from the big island (Hawai'i) and Maui (Bottom).

Why is this cool? Salts in the glue allows water absorption from the environment, and by changing salt composition in their glue spiders can rapidly acclimate to its environment. We are already seeing differences in silk properties for the same specie of spider that lives in different islands. Seeing these differences among populations within a species suggests that silk materials may evolve much faster than anticipated.