Fritz Vollrath

Changes in element composition along the spinning duct in a Nephila spider.

Abstract. The silk gland of the golden orb spider Nephila edulis connects to the exit spigot through a long S-shaped duct that assists in the formation of the thread. Previous evidence suggests that the epithelium of the distal (last) part of the duct is specialized for ion transport and that a proton pump is involved in this process. Here, we present evidence from SEM (scanning electron microscope)-EDAX (energy dispersive X-ray) microanalysis of rapidly frozen material maintained at approximately –150°C and from the use of pH indicators that the element composition and pH change progressively as the dragline silk dope (spinning solution) passes down the duct to form the thread. Na+ and Cl– composition decreased while K+ and P and S increased. Indicators suggested that the pH dropped from 6.9±0.1 to 6.3±0.1. These novel findings suggest that the absorption of Na+ and secretion of the more chaotropic K+ may help the silk protein molecules to refold while the secretion of H+ may assist in this process and reduce the repulsive charges on them. This in turn may allow the molecules to approach one another more closely to crystallize. Thus precise control of the ionic environment within the spiders spinning duct may be important in forming a tough insoluble thread and when devising mimetic processes to spin silk proteins industrially.

Movements and corridors of African elephants in relation to protected areas.

Understanding how mammals satisfy their need for space in fragmenting ecosystems is crucial for ecosystem conservation. Using state-of-the-art global positioning system (GPS) technology we tracked 11 focal African elephants (Loxodonta africana) in Kenya at 3-hourly fix intervals and collected between 34 and 406 days per individual. Our recordings gave a high spatio-temporal resolution compared to previous studies and allowed novel insights into range use. The actual ranges of the tracked elephants are smaller than usually represented. Moreover, the ranges in our sample were complex and not confined to officially designated protected areas, except where fenced. All the unfenced elephants in our sample had distinct ‘home sectors’ linked by ‘travel’ corridors. Within each home sector the elephants concentrated in favourite ‘core zones’. Such core zones tended to lie in protected areas whereas corridors typically crossed unprotected range. Elephants moved significantly faster along corridors than elsewhere in their range, which suggests awareness of danger outside the protected area. We conclude that understanding the complex use of an animal’s range is crucial for conservation planning aiming to balance animal interests with those of human beings that co-habit in their range.

Social dominance, seasonal movements, and spatial segregation in African elephants: a contribution to conservation behavior

The structure of dominance relationships among individuals in a population is known to influence their fitness, access to resources, risk of predation, and even energy budgets. Recent advances in global positioning system radio telemetry provide data to evaluate the influence of social relationships on population spatial structure and ranging tactics. Using current models of socio-ecology as a framework, we explore the spatial behaviors relating to the maintenance of transitive (i.e., linear) dominance hierarchies between elephant social groups despite the infrequent occurrence of contests over resources and lack of territorial behavior. Data collected from seven families of different rank demonstrate that dominant groups disproportionately use preferred habitats, limit their exposure to predation/conflict with humans by avoiding unprotected areas, and expend less energy than subordinate groups during the dry season. Hence, our data provide strong evidence of rank derived spatial partitioning in this migratory species. These behaviors, however, were not found during the wet season, indicating that spatial segregation of elephants is related to resource availability. Our results indicate the importance of protecting preexisting social mechanisms for mitigating the ecological impacts of high density in this species. This analysis provides an exemplar of how behavioral research in a socio-ecological framework can serve to identify factors salient to the persistence and management of at risk species or populations.

Elephants avoid costly mountaineering

Understanding the behavioural decisions underlying animal movements is a major challenge. Here we report evidence for the importance of the abiotic terrain feature ‘gradient’ in guiding the movements of African savannah elephants (Loxodonta africana). Global Positioning System (GPS) tracking data overlaid onto digital elevation and surface gradient models show that elephants tend to avoid steep slopes. Energy calculations suggest that even minor hills are considerable energy barriers for heavy animals.

Silk cocoon (Bombyx mori): Multi-layer structure and mechanical properties

Bombyx mori cocoon is a natural composite made of silk fibre with a distinctive multi-layer structure that provides mechanical protection for its biological functions. Here we investigate the components, structure and mechanical properties of cocoon layers, and quantify the contributions of the multi-layer structure to the mechanical properties of cocoon. A better understanding of the multi-layer mechanism of a natural composite could help the further design of biomimetic multiscale artificial materials.

There are many more lessons still to be learned from spider silks

At the heart of ‘copying from Nature’ lies the implied assumptions that, firstly, researchers understand what they propose to copy and that, secondly, industrialists have found ways to successfully integrate the many requirements necessary for a reliable bio-mimetic copying process. Here we explore the traits of native silks and examine the assertions associated with man-made copies focusing on the question: why do the various assertions and claims matter, and why is a critical evaluation appropriate for a special themed issue on biomimetic soft matter?

The spinning processes for spider silk

This paper summarizes recent work in our groups on the factors that influence the formation of spider silks during the spinning process. The review encompasses: (a) extrusion variables that greatly affect the mechanical properties of the silk filaments; such as rate and temperature at spinning as well as the post-drawn treatment and (b) other factors affecting the conformation transition of the spider silk proteins (spidroin) such as pH and metallic ions. The observations taken together imply that the spinning process is at least as central as, and probably more important than, the composition of the raw protein spinning solution. This conclusion leads us to suggest that in the future high-performance, artificial spider silks may be spun from a range of solutions of silk and synthetic proteins.

Two mechanisms for supercontraction in Nephila spider dragline silk.

Supercontraction in dragline silk of Nephila edulis spider is shown to have two distinct components revealed by single fiber measurements using dynamic mechanical thermal analysis. The first component relies on a contraction of maximum 13% and seems to be associated with relaxation processed through the glass transition, T(g), as is induced by increasing temperature and/or humidity. The second component is induced by liquid water to the total contraction of 30%. The T(g)-induced contraction is linearly correlated with the restraining stress on the fiber, and the mechanical properties of the partially contracted silk have mechanical profiles that differ from both native and fully supercontracted fibers. Here we present novel supercontraction data and discuss their structural origins, examining the relaxation of stretched orientation in the different primary structure sequences.

African bees to control African elephants.

Abstract. Numbers of elephants have declined in Africa and Asia over the past 30xa0years while numbers of humans have increased, both substantially. Friction between these two keystone species is reaching levels which are worryingly high from an ecological as well as a political viewpoint. Ways and means must be found to keep the two apart, at least in areas sensitive to each species survival. The aggressive African bee might be one such method. Here we demonstrate that African bees deter elephants from damaging the vegetation and trees which house their hives. We argue that bees can be employed profitably to protect not only selected trees, but also selected areas, from elephant damage.

β‐Silks: Enhancing and Controlling Aggregation

It appears that fiber-forming proteins are not an exclusive group but that, with appropriate conditions, many proteins can potentially aggregate and form fibrils; though only certain proteins, for example, amyloids and silks, do so under normal physiological conditions. Even so, this suggests a ubiquitous aggregation mechanism in which the protein environment is at least as important as the sequence. An ideal model system in which forced and natural aggregation has been observed is silk. Silks have evolved specifically to readily form insoluble ordered structures with a wide range of structural functionality. The animal, be it silkworm or spider, will produce, store, and transport high molecular weight proteins in a complex environment to eventually allow formation of silk fibers with a variety of mechanical properties. Here we review fiber formation and its prerequisites, and discuss the mechanism by which the animal facilitates and modulates silk assembly to achieve controlled protein aggregation.