Factors influencing the susceptibility of anurans to motion sickness

We examined the propensity for motion sickness in five anuran species, conc entrating our efforts on the treefrog Rhacophorus sclegelii, because it had shown the greatest susceptibility to motion sickness in a previous study. We used parabolic flight as our provocative stimulus and fed all specimens a known volume of food 1.5-3 h before flight. The presence of vomitus in a frog's cage was our indicator of motion sickness. Significantly more emesis was observed in flight-exposed than in control R. schlegelii (P < 0.05). T here was no sex difference in susceptibility to motion sickness (P > 0.5). Individuals that vomited were significantly larger (P < 0.02) than those th at did not. Among microgravity-treated frogs, those that vomited spent on a verage 85% more time airborne and tumbling in microgravity than those that did not vomit (P = 0.031). Our data support the view that postural instabil ity and sensory conflict are elements of motion sickness in anurans. Specif ically, conflicts between tactile, vestibular and visual input seem essenti al for producing motion-induced emesis in anurans. Since the factors that i nduce motion sickness in R. schlegelii are the same ones that produce motio n sickness in humans, arboreal frogs may be useful alternative models to ma mmals in motion sickness research.