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Cardiovascular Responses of Snakes to Gravitational GradientsSnakes are useful vertebrates for studies of gravitational adaptation, owing to their elongate body and behavioral diversification. Scansorial species have evolved specializations for regulating hemodynamics during exposure to gravitational stress, whereas, such adaptations are less well developed in aquatic and non-climbing species. We examined responses of the amphibious snake,\italicize (Nerodia rhombifera), to increments of Gz (head-to-tail) acceleration force on both a short- and long-arm centrifuge (1.5 vs. 3.7 m radius, from the hub to tail end of snake). We recorded heart rate, dorsal aortic pressure, and carotid arterial blood flow during stepwise 0.25 G increments of Gz force (referenced at the tail) in conscious animals. The Benz tolerance of a snake was determined as the Gz level at which carotid blood flow ceased and was found to be significantly greater at the short- than long-arm centrifuge radius (1.57 Gz vs. 2.0 Gz, respectively; P=0.016). A similar pattern of response was demonstrated in semi-arboreal rat snakes,\italicize{Elaphe obsoleta}, which are generally more tolerant of Gz force (2.6 Gz at 1.5m radius) than are water snakes. The tolerance differences of the two species reflected cardiovascular responses, which differed quantitatively but not qualitatively: heart rates increased while arterial pressure and blood flow decreased in response to increasing levels of Gz. Thus, in both species of snakes, a reduced gradient of Gz force (associated with greater centrifuge radius) significantly decreases the Gz level that can be tolerated.
Document ID
20020051878
Document Type
Preprint (Draft being sent to journal)
Authors
Hsieh, Shi-Tong T. (NASA Ames Research Center Moffett Field, CA United States)
Lillywhite, H. B. (NASA Ames Research Center Moffett Field, CA United States)
Ballard, R. E. (NASA Ames Research Center Moffett Field, CA United States)
Hargens, A. R. (NASA Ames Research Center Moffett Field, CA United States)
Holton, Emily M.
Date Acquired
August 20, 2013
Publication Date
January 1, 1998
Subject Category
Life Sciences (General)
Meeting Information
Experimental Biology ''98(San Francisco, CA)
Funding Number(s)
PROJECT: RTOP 199-80-02-05
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.