THE BEHAVIORAL REACTIONS OF A SNAKE AND A TURTLE TO ABRUPT DECREASES IN GRAVITY

We report here on the behavioral reaction of two reptiles to abrupt de creases in gravity. One striped rat snake, Elaphe quadrivirgata, and t hree striped-neck pond turtles, Mauremys japonica, were exposed to mic rogravity (mu-G) on parabolic flight, during the filming of a document ary for the NHK television station in Japan. The video films revealed that the snake reflexively responded to the shift from hyper- to hypog ravity by taking up a defensive posture-on the first parabola, the sna ke struck at itself. The turtles actively extended their limbs and hyp er-extended their neck in mu-G, a posture which is identical to that d isplayed during their contact ''righting reflex'', when placed upside- down in normal gravity. The aggressive display of the snake was unexpe cted, although the righting response of the turtles was consistent wit h that shown by other vertebrates, including fish and mammals, exposed to mu-G. An implication of these observations is that the afferent si gnal 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 record s for any reptiles exposed to hypogravity.