Correlating Spiderling Growth with Changes in Spider Silk Properties

Background

Spider dragline silk is one of the most studied biological fibers. It is extremely strong, stretchy, and tough, which makes it interesting both as a material and for medical use, since it is also biocompatible and biodegradable.^1–3  However, we still don't fully understand how spiders turn their liquid silk protein (the "spinning dope") into a solid fiber that is tougher than silkworm silk and even Kevlar.^4,5 Part of the problem is that the sequence of silk proteins (spidroins) alone cannot explain how strong native silk fibers are.^6,7 This suggests that the structure and function of the silk gland itself also play an important role, one that has been largely overlooked. So far, silk formation has only been studied in adult spiders. We know it is a tightly controlled process: the liquid silk stored in the gland experiences changes in pH and ion concentration, along with increasing shear forces, causing the proteins to assemble into a solid fiber. This fiber is then pulled out through the spinneret. ^8–10

Recent work from our Anna Rising research group, using the orb-weaver spider Larinioides sclopetarius, showed that different regions of the silk gland are lined with different cell types, each contributing different components to the final silk, including spidroins and other supporting molecules.¹¹ Other studies have used micro-CT scanning to map the 3D structure of the gland and spinneret in adult spiders. ^12,13 Despite this progress in adult spiders, we know that silk properties change substantially with spider size, even within the same species, as spiders grow.^14–17 However, very little is known about how the silk-producing system itself develops, or whether gland structure and silk properties mature together over time. Only a handful of studies, mostly in the silkworm Bombyx mori, have looked at how silk glands develop.^18–22 For spiders, how the silk system changes from newly hatched spiderlings to juveniles and adults remains completely unexplored.

Project description

This project will start in spring, as soon as the first Larinioides sclopetarius spiders can be collected. The spiders will be kept in the lab and fed until they lay cocoons. After the spiderlings hatch, they will be maintained individually, and their growth and body size will be monitored for at least three months. At regular intervals, dragline silk will be collected from each spiderling and analyzed using mechanical testing (tensile tests) and structural/morphological methods (electron microscopy and FTIR) to characterize its material properties. These properties will then be linked with spiderling size to assess how silk performance changes over development. The student will gain insights into morphogenesis during development, as well as the analytical methods used to study follow it.

Aim and Hypothesis

As spiders grow from spiderlings to adults, their silk glands might go through a series of developmental changes. These anatomical changes lead to gradual changes in spider silk properties as spiderlings age. We hypothesize that changes in spider size and their gland structure, are linked to changes in the silk fibers, including their morphology, secondary structure, and mechanical properties.

Requirements

Interest in working with spiders and in learning analytical/chemical methods. Good command of English, both written and spoken.