TOLERANCE OF SNAKES TO HYPERGRAVITY

Sensitivity of carotid blood flow to increased gravitational force act ing in the head-to-tail direction (+G(z)) was studied in diverse speci es of snakes hypothesized to show adaptive variation of response. Tole rance to increased gravity was measured as the maximum graded accelera tion force at which carotid bloodflow ceased and was shown to vary acc ording to gravitational adaptation of species defined by their ecology and behavior. Multiple regression analysis showed that gravitational habitat, but not body length, had a significant effect on G(z) toleran ce. At the extremes, carotid blood flow decreased in response to incre asing G force and approached zero near +1G(z) in aquatic and ground-dw elling species, whereas in climbing species carotid flow was maintaine d at forces in excess of +2G(z). Tolerant (arboreal) species were able to withstand hypergravic forces of +2 to +3G(z) for periods up to 1h without cessation of carotid blood flow or loss of body movement and t ongue picking. Data suggest that the relatively right skin characteris tic of tolerant species provides a natural antigravity suit and is of prime importance in counteracting G(z) stress on blood circulation.