Microstructure and mechanical properties of different keratinous horns

Abstract

Animal horns play an important role during intraspecific combat. This work investigates the microstructure and mechanical properties of horns from four representative ruminant species: the bighorn sheep (), domestic sheep (), mountain goat () and pronghorn (), aiming to understand the relation between evolved microstructures and mechanical properties. Microstructural similarity is found where disc-shaped keratin cells attach edge-to-edge along the growth direction of the horn core (longitudinal direction) forming a lamella; multiple lamellae are layered face to face along the impact direction (radial direction, perpendicular to horn core growth direction), forming a wavy pattern surrounding a common feature, the tubules. Differences among species include the number and shape of the tubules, the orientation of aligned lamellae and the shape of keratin cells. Water absorption tests reveal that the pronghorn horn has the largest water-absorbing ability due to the presence of nanopores in the keratin cells. The loading direction (compressive and tensile) and level of hydration vary among the horns from different species. The differences in mechanical properties among species may relate to their different fighting behaviours: high stiffness and strength in mountain goat to support the forces during stabbing; high tensile strength in pronghorn for interlocked pulling; impact energy absorption properties in domestic and bighorn sheep to protect the skull during butting. These design rules based on evolutionary modifications among species can be applied in synthetic materials to meet different mechanical requirements.

Growing Medium Type Affects Organic Fertilizer Mineralization and CNPS Microbial Enzyme Activities

“…We showed in the current study that horn is a very interesting organic fertilizer in terms of nutrient supply with no burst effect and the response intensity depends, as hypothesized, on the GM type. Despite the lowest C:N and C:P ratios, horn induced the weakest releases of nutrient as hypothesized (Figure 2) mainly due to its physical (high density material and hard fibers) and chemical recalcitrance necessitating the protein depolymerization of keratin (i.e., proteins) (Table S1) by microbes [77][78][79]. Horn does not only contain nitrogen, as frequently stated, but it does contain other nutrients necessary for plants and microbes such as P, among many others (Table 1; Table S1) with typical dynamics depending on the GM type (Figure 2).…”

Effects of Graphene Oxide on the Structure and Properties of Regenerated Wool Keratin Films

“…The outstanding physical properties of wool fibers are derived from their complex chemical groups on keratin macromolecules and their fine arrangement [9,10,11]. In the dissolving process of wool fibers, the secondary structure between keratin molecules is destroyed, and these broken molecular chains are disordered in the solution.…”

Living alone or moving in herds? A holistic approach highlights complexity in the social lifestyle of Cretaceous ankylosaurs

“…Furthermore, the significant reinforcing role of keratinous sheaths (e.g. Zhang et al, 2018), the so-called exaggerated epidermal structures, which must have covered the osteoderms, especially the spikes, to a great extent in all ankylosaurs (Burns and Currie, 2014;Brown et al, 2017), are not considered in these claims of inefficient defence, either.…”