20th International Congress of Arachnology

Research Centre, Slovenian Academy of Sciences and Arts,

Novi trg 2, P.O. Box 306, SI-1001 Ljubljana, Slovenia;

Department of Polymer Science, The University of Akron,

Akron OH 44325-3909, USA; 4Department of Biological

Sciences, Virginia Tech, Blacksburg Virginia 24061, USA

blackledge@uakron.edu

The evolution of viscid aggregate glues is associated with

the radiation of orb-weaving spiders. Aggregate glue

forms the sticky droplets on prey capture threads and is

a composite of viscoelastic glycoproteins and organic

salts. While the glycoproteins are the primary adhesive,

the salts absorb atmospheric water, thereby plasticizing

the threads, and directly solvate the proteins, helping

the glycoproteins to spread across surfaces. The high

extensibility of the droplets allows them to extend in a

“suspension bridge” system that also recruits adhesion

across the entire thread’s length. Here, we explore how

each of these elements is responds responsive to humid-

ity and results in the capture threads of diverse species

of spiders function optimally at different humidities. We

argue that the chemical composition of the organic salts

is a highly evolvable mechanism that “tunes” orb function

to particular microhabitats, and that this principle can be

exploited in the design of synthetic smart adhesives.

Keywords: adhesion, aggregate, biomechanics, biomate-

rials, orb web, prey capture, viscid silk

Oral presentation

Analysis of spider silk structural variability

using small and wide-angle X-ray diffraction

Sean J. Blamires

Evolution & Ecology Research Centre, School of

Biological, Earth & Environmental Sciences, The Uni-

versity of New South Wales, Sydney 2052, Australia

s.blamires@unsw.edu.au

Spider major ampullate (MA) silk is nature’s toughest

material. Attempts to synthesise silk-like fibers have so far

been unsuccessful. One reason for this is that the structures

and properties of MA silk are variable across environments.

The high strength and extensibility in MA silk is a product

of its protein arrangements and tertiary structures. It is

becoming evident that a more complete elucidation of the

molecular mechanism behind the property variations of

spider MA silk lies in understanding the evolution of spider

silk performance. Small-angle X-ray diffraction imaging

of silks produces an amorphous ring and equatorial

streak allowing identification of the structure of the fiber

along its meridian. Accordingly, it has been successfully

used to elucidate the structure of the amorphous region.

Wide angle X-ray diffraction on the other hand is useful

for determining the size, alignment and orientation of

crystalline structures. A combination of both small and

wide-angled diffraction is essential for gaining a thorough

insight into the structures of spider silk proteins. Because

most of the work correlating protein structure with

mechanical performance has thus far concentrated on the

high performing silks of web building spiders, we do not

understand the processes facilitating variations in silk per-

formance at molecular scales across the spider phylogeny. I

have performed experiments manipulating the diet of dif-

ferent spiders and examined the crystalline and amorphous

structures of the silk proteins using small and wide angle

X-ray scattering and found a combination of crystalline

and amorphous features synergistically induce variations

in protein strength and extensibility. Moreover, the mecha-

nisms of structural variability seem to be consistent across

different spiders. Future research will use SAXS/WAXS

analyses to examine the protein structures in the silks of a

wider range of web building and non-web building spiders.

Keywords: silk, nano-structures, X-ray diffraction properties

Oral presentation

Spiders in sloping blockfield habitats in the

Fichtel Mountains (NE Bavaria, Germany)

Theo Blick

, Michael-Andreas Fritze

Callistus - Gemeinschaft für Zoologische & Ökologische

Untersuchungen, Heidloh 8, 95503 Hummeltal,

Germany;

Dahlienstr. 15, 95488 Eckersdorf, Germany

blick@callistus.de

Motivated by the research on stony debris (talus) habitats

of the spider and invertebrate fauna by Ruzicka (Czech

Republic) and Molenda (Germany/Belgium to Italy), we

obtained funding for research on these special habitats

DENVER MUSEUM OF NATURE & SCIENCE

REPORTS

No. 3, July 2, 2016

Cushing