Document Detail

Ontogenetic changes in the structural stiffness of the tailstock of bottlenose dolphins (Tursiops truncatus).
MedLine Citation:
PMID:  18840654     Owner:  NLM     Status:  MEDLINE    
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.
S A Etnier; W A McLellan; J Blum; D A Pabst
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of experimental biology     Volume:  211     ISSN:  0022-0949     ISO Abbreviation:  J. Exp. Biol.     Publication Date:  2008 Oct 
Date Detail:
Created Date:  2008-10-08     Completed Date:  2008-12-11     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0243705     Medline TA:  J Exp Biol     Country:  England    
Other Details:
Languages:  eng     Pagination:  3205-13     Citation Subset:  IM    
Department of Biological Sciences, Butler University, Indianapolis, IN 46208, USA.
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MeSH Terms
Age Factors
Animals, Newborn
Body Size*
Bottle-Nosed Dolphin / anatomy & histology*,  embryology,  growth & development*
Fetus / anatomy & histology
Swimming / physiology
Grant Support
5 F32 AR 08599-03/AR/NIAMS NIH HHS

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