The Behavioral Reactions of a Snake and a Turtle to Abrupt Decreases in Gravity

概要

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We report here on the behavioral reaction of two reptiles to abrupt decreases in gravity. One striped rat snake, Elaphe quadrivirgata, and three striped-neck pond turtles, Mauremys japonica, were exposed to microgravity (μ-G) on parabolic flight, during the filming of a documentary for the NHK television station in Japan. The video films revealed that the snake reflexively responded to the shift from hyper- to hypogravity by taking up a defensive posture-on the first parabola, the snake struck at itself. The turtles actively extended their limbs and hyper-extended their neck in μ-G, a posture which is identical to that displayed during their contact "righting reflex", when placed upside-down in normal gravity. The aggressive display of the snake was unexpected, although the righting response of the turtles was consistent with that shown by other vertebrates, including fish and mammals, exposed to μ-G. An implication of these observations is that the afferent signal for the righting reflex of vertebrates in normal gravity must be the unloading of ventral receptors in the sensory system, rather than the loading of dorsal receptors. These are the first behavioral records for any reptiles exposed to hypogravity.
社団法人日本動物学会の論文
1993-06-15