A Rubber-Like Protein in Insect Cuticle

Abstract

1. A new type of hyaline, colourless cuticle, called rubber-like cuticle, is described and analysed qualitatively with respect to mechanical behaviour, structure and composition. Externally it is covered by ordinary thin epicuticle, but otherwise it represents the simplest type of cuticle known and consists only of thin continuous lamellae of chitin (0-2 µ) separated and glued together by an elastic protein, resilin, not hitherto described. There are only traces of water-soluble substances present and resilin sometimes occurs as pure, hyaline patches more than 100 µ thick and suitable for macroscopic experiments. 2. In all physical respects, resilin behaves like a swollen isotropic rubber but the rigid experimental proof is given elsewhere (Weis-Fogh, 1961). An outstanding feature is the complete lack of flow not paralleled by other natural or synthetic rubbers. 3. Resilin resembles elastin but it is devoid of colour and has a different and characteristic amino-acid composition (Bailey & Weis-Fogh, 1961). The nature of the cross-linkages is unknown at present but they are extremely stable, of a co-valent type and different from other known cross-linkages in proteins. This accounts for its insolubility and resistance to all agents which do not break the peptide backbone. 4. Resilin is a structure protein in which the primary chains show little or no tendency to form secondary structures; they are bound together in a uniform three-dimensional network (the tertiary structure) with no potential limits as to size.

Exaggerated sexually selected weapons maintained with disproportionately low metabolic costs in a single species with extreme size variation

“…Body parts were separated, dried at 50°C for 72 hr until a stable mass was reached, and weighed to the nearest 0.1 mg. Each sample was placed in separate 1.7-ml microcentrifuge tube and submerged in 18.5 U/ml of the protease papain within 100 mM Tris-HCl pH 7 to activate this proteolytic enzyme. Papain targets tissue with higher metabolic capacity for digestion, leaving sclerotized tissue such as cuticle relatively intact (Weis-Fogh, 1960). After digestion, samples were washed with EtOH (70%), dried for 72 hr and weighed again.…”

Dimensional analysis of spring-wing systems reveals performance metrics for resonant flapping-wing flight

“…If an oscillating wing is coupled to an elastic element such as a spring, the kinetic energy from the wing could be stored as elastic energy at the end of the wing-stroke and returned after stroke reversal. Many insects [1][2][3][4][5], birds [5,6] and even bats [7] have spring-like elements in the form of elastic materials in their thoraxes, muscles and tendons that may aid in reducing the energetic demands of flapping flight and improving flight efficiency (resonance) (figure 1a). However, the evidence that insects and birds operate near resonance largely relies on corelational observations of wingbeat frequency and wing inertia [9,10], or energetics arguments comparing metabolic and aerodynamic power [5,11,12].…”

Dimensional analysis of spring-wing systems reveals performance metrics for resonant flapping-wing flight

“…Series elastic elements in flapping wing flight may similarly be found in the muscle tendon units of birds [18,31]. In insects, series elasticity can arise from elastic tendons [3], elasticity in the wing hinge [33] or within the flight power muscle [23]. For simplicity of experiment design and to examine the differences between series and parallel systems, we analyze the series elastic spring-wing configuration.…”

“…If an oscillating wing is coupled to an elastic element such as a spring, the kinetic energy from the wing could be stored as elastic energy at the end of the wing-stroke and returned after stroke reversal. Many insects [13,14,22,33,34], birds [18,34], and even bats [24] have spring-like elements in the form of elastic materials in their thoraxes, muscles, and tendons that may aid in reducing the energetic demands of flapping flight and improving flight efficiency (resonance) (Fig. 1a).…”

“…The primary mechanism of elastic energy storage in insects is resilin, a highly-resilient elastic material first identified in patches of the locust exoskeleton was discovered and characterized in the 1960's by Weis-Fogh [22,33,34] (and subsequently identified in many other arthropods). It was shown to return greater than 97% of stored elastic energy, suggesting that insects have resilient components within their thorax that can facilitate efficient energy exchange and return.…”