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Spinal deformities among captive sand tiger sharks, Carcharias taurus, are unfortunately common, and abnormal swimming behavior due to constrained aquarium space has been hypothesized to contribute to the development of this condition. Public aquaria across the United States were surveyed for number, condition (healthy vs. affected), and total length of resident C. taurus specimens and for dimensions of their aquaria. They were also asked to record 10 minute video segments of individual C. taurus swimming in lateral view. Total length of sharks, regardless of condition, averaged 225 ± 5 (mean ± SE) cm. Aquarium shapes varied widely, but aquaria held median volumes of 1.03 X 106 L, and were a median of 4.6 m in depth and 20.7 m in greatest horizontal distance. The greatest horizontal distance of aquaria was negatively correlated with disease prevalence of resident populations in a logarithmic fashion (r = 0.72). Behaviorally, sharks were assessed for total time and percentage of time spent swimming in a specific direction (clockwise, counter-clockwise, or linear), in a glide, and tail-beat duration. Regardless of condition, C. taurus spent a median of 98.9% of time swimming and 0.62% of time gliding. Healthy sharks spent a median of 0.67% gliding versus a median of 0% for afflicted sharks (p= 0.036), suggesting an increased swim-to-glide ratio among the latter group. All sharks swam asymmetrically in either a clockwise or counter-clockwise direction for a median of 99.7% of observed time. Affected specimens had tail beat durations of 3.37 ± 0.23 s vs. 2.72 ± 0.10 s for healthy sharks (p = 0.005). The increase in swim-to-glide ratios and inordinate time spent swimming asymmetrically for all affected sharks support the hypothesis that swimming patterns induced by captive exhibits may contribute to spinal deformities in C. taurus due to more stress placed on the spine. Large, complex aquarium designs are recommended in the planning of new exhibits to discourage stereotypical swimming behavior and also to provide sufficient length for sharks to complete natural swimming repertoires. Comprehensive behavioral enrichment activities that encourage complex movement are also recommended as well as considerations such as even weight distribution of the animal during capture, sourcing of appropriately aged sharks, and nutritional supplementation.

ABSTRACT Feeding performance is an organism's ability to capture and handle prey. Although bite force is a commonly used metric of feeding performance, other factors such as bite pressure and strike speed are also likely to affect prey capture. Therefore, this study investigated static bite force, dynamic speeds, and predator and prey forces resulting from ram strikes, as well as bite pressure of the king mackerel, Scomberomorus cavalla, in order to examine their relative contributions to overall feeding performance. Theoretical posterior bite force ranged from 14.0-318.7 N. Ram speed, recorded with a rod and reel incorporated with a line counter and video camera, ranged from 3.3-15.8B L/s. Impact forces on the prey ranged from 0.1-1.9 N. Bite pressure, estimated using theoretical bite forces at three gape angles and tooth cross-sectional areas, ranged from 1.7-56.9 MPa. Mass-specific bite force for king mackerel is relatively low in comparison with other bony fishes and sharks, with relatively little impact force applied to the prey during the strike. This suggests that king mackerel rely on high velocity chases and high bite pressure generated via sharp, laterally compressed teeth to maximize feeding performance. J. Exp. Zool. 323A: 399-413, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Approximately 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. [ABSTRACT FROM AUTHOR]

The design of minimum-weight structures that retain their integrity under dynamic loading regimes has long challenged engineers. One solution to this problem found in both human and biological design is the optimization of weight and strength by hollowing a structure and replacing its inner core with supportive struts. In animals, this design is observed in sand dollar test, avian beak, and the cancellous bone of tetrapod limbs. Additionally, within the elasmobranch fishes, mineralized trabeculae (struts) have been reported in the jaws of durophagous myliobatid stingrays (Elasmobranchii: Batoidea), but were believed to be absent in basal members of the batoid clade. This study, however, presents an additional case of batoid trabeculation in the lesser electric ray, Narcine brasiliensis (Torpediniformes). The trabeculae in these species likely play different functional roles. Stingrays use their reinforced jaws to crush bivalves, yet N. brasiliensis feeds by ballistically protruding its jaws into the sediment to capture polychaetes. In N. brasiliensis, trabeculae are localized to areas likely to experience the highest load: the quadratomandibular jaw joints, hyomandibular-cranial joint, and the thinnest sections of the jaws immediately lateral to the symphyses. However, the supports perform different functions dependent on location. In regions where the jaws are loaded transversely (as in durophagous rays), "load leading" trabeculae distribute compressive forces from the cortex through the lumen of the jaws. In the parasymphyseal regions of the jaws, "truss" trabeculae form cross-braces perpendicular to the long axes of the jaws. At peak protrusion, the jaw arch is medially compressed and the jaw loaded axially such that these trabeculae are positioned to resist buckling associated with excavation forces. "Truss" trabeculae function to maintain the second moment of area in the thinnest regions of the jaws, illustrating a novel function for batoid trabeculation. Thus, this method of structural support appears to have arisen twice independently in batoids and performs strikingly different ecological functions associated with the distribution of extreme loading environments., (Copyright (c) 2004 Wiley-Liss, Inc.)