Mechanical properties of sand tiger sharkCarcharias taurusvertebrae in relation to spinal deformity

Abstract

SUMMARYApproximately 35% of sand tiger sharks (Carcharias taurus) in public aquaria exhibit spinal deformities ranging from compressed vertebrae and loss of intervertebral space to dislocated spines with vertebral degeneration and massive spondylosis caused by excessive mineralization both within vertebrae and outside the notochordal sheath. To identify the mechanical basis of these deformities, vertebral centra from affected (N=12) and non-affected (N=9) C. taurus were subjected to axial compression tests on an MTS 858 Bionix material testing system, after which mineral content was determined. Vertebral centra from affected sharks had significantly lower mineral content and material behavior in nearly all variables characterizing elasticity, plasticity and failure. These mechanical deficiencies are correlated with size at capture, capture method, vitamin C and zinc deficiency, aquarium size and swimming behavior in public aquaria. Non-affected C. taurus had greater stiffness and toughness even though these properties are generally incompatible in mineralized structures, suggesting that the biphasic (mineralized, unmineralized phases) nature of chondrichthyan vertebrae yields material behavior not otherwise observed in vertebrate skeletons. However, vertebral centra from non-affected sharks had lower mineral content (33%), stiffness (167 MPa), yield strain (14%) and ultimate strength (16 MPa) than other species of sharks and bony vertebrates, indicating that biomechanical precautions must be taken in the husbandry of this species.

Mechanical properties of the hyomandibula in four shark species

“…The apparatus was placed into elasmobranch ringer's solution (Forster et al, 1972) for at least 30 min to allow the putty to set. Once set, the putty had an elastic modulus of 3.19 GPa, which is three orders of magnitude higher than the modulus of articular cartilage and about one order of magnitude higher than that of previously tested mineralized shark cartilage (Korhonen et al, 2002;Jin and Lewis, 2004;Stolz et al, 2004;Porter et al, 2006Porter et al, , 2013Macesic and Summers, 2012;Ferrara et al, 2013;Huber et al, 2013;Liu et al, 2014; Table S1). The hyomandibula was then placed in the materials testing machine so the discs were parallel with the compression platens and the hyomandibula could be loaded along the longitudinal axis (Fig.…”

Ultrastructural, material and crystallographic description of endophytic masses – A possible damage response in shark and ray tessellated calcified cartilage

“…EPMs could represent an earlier stage in the formation of the massive hypercalcifications/fusions described by Maisey (2013). Many authors have also observed pathologic, mineralized masses encasing portions of the vertebral column in sharks (Hoenig & Walsh, 1983;Huber et al, 2013;Officer et al, 1995;Porter et al, 2006), particularly in captive sandtiger sharks (Carcharias taurus) with spinal deformities (Fig. 11A), encasing sites of former vertebral fracture or dislocation (Fig.…”

“…The endoskeletons of sharks and rays (elasmobranch fishes) are typically described as being composed of unmineralized cartilage and two distinct types of calcified cartilage, which differ in their location and ultrastructure. Areolar calcified cartilage is a highly cellular, net-like mineralized tissue, with the cells occupying the holes in the net, that is only found in the centra of the vertebral column (Clement, 1992;Compagno 1988;Huber et al, 2013;Porter et al, 2006). In contrast, tessellated calcified cartilage comprises the remainder and vast majority of the endoskeleton (Fig.…”

Feeding in billfishes: inferring the role of the rostrum from a biomechanical standpoint

“…This approach is applicable because many biological structures can be treated as beams (e.g. trees, echinoderms, vertebral columns; Koehl, 1977;Baumiller, 1993;Ennos, 1993;Huber et al, 2013), and beam theory also facilitates better comprehension of form and function relationships by teasing apart factors that contribute to a biological beam's performance under loading. A beam's resistance to bending is given by the flexural stiffness EI, which is a function of both its material properties (via Young's modulus, E) and its geometry (via second moment of area, I ) (Koehl, 1976(Koehl, , 1977Wainwright et al, 1976;Biewener and Full, 1992).…”