Ontogenetic changes in the structural stiffness of the tailstock of bottlenose dolphins (Tursiops truncatus).
نویسندگان
چکیده
Late-term fetal bottlenose dolphins (Tursiops truncatus) are bent ventrolaterally en utero, requiring extreme flexibility of the axial skeleton and associated soft tissues. At birth, neonatal dolphins must immediately swim to the surface to breath, yet the dorsoventral oscillations used during locomotion may be compromised by the lateral flexibility evident in the fetus. The unique fetal position of dolphins, coupled with their need to swim at birth, places conflicting mechanical demands on the tailstock. Our previous research demonstrated that neonatal dolphins possess laterally placed, axial muscles that are functionally specialized to actively maintain the straightened posture of the tailstock. Here, we investigated the development of passive lateral stability in the tailstock of bottlenose dolphins by performing whole-body bending tests on an ontogenetic series of stranded dolphin specimens (N=15), including fetuses, neonates and juveniles (total length 58-171 cm). Structural stiffness increased, while overall body curvature decreased, with increasing body length. Scaling analyses suggest that increased structural stiffness is due to increases in size and probably changes in the passive material properties of the tailstock through ontogeny. The neutral zone was approximately constant with increasing size, while the relative neutral zone (neutral zone/total length) decreased. The lateral stability of the tailstock appears to be controlled by a combination of active and passive systems and the role of these systems varies through ontogeny. While neonates use active, muscular mechanisms to limit lateral deformations of the tailstock, the stability of the maturing tailstock is due primarily to its passive tissue properties.
منابع مشابه
Ontogenetic changes in the structural stiffness of the tailstock of bottlenose
INTRODUCTION Late-term fetal bottlenose dolphins (Tursiops truncatus) exhibit extreme levels of lateral flexion prior to birth (Fig.1). En utero, the fetus is bent laterally and ventrally such that the tail flukes are juxtaposed to the throat region (Slijper, 1966; Cockcroft and Ross, 1990). Evidence of this extreme posture can be seen in the fetal folds (Fig.1), which can persist for several w...
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ورودعنوان ژورنال:
- The Journal of experimental biology
دوره 211 Pt 20 شماره
صفحات -
تاریخ انتشار 2008