Interspecific variation in the emetic response of anurans.

1. The emetic response of seven species (four genera) of frogs to apomorphine hydrochloride, copper sulfate, antimonyl potassium tartrate and mechanical stimulation at the esophageal orifice was surveyed. Xenopus laevis and Rhacophorus schlegelii were more sensitive to systemically administered apomorphine than were the other species tested. 2. The sensitivity of Rana rugosa to apomorphine varied with the season. 3. All of the species showed vigorous vomiting behavior after the oral administration of either copper sulfate or antimonyl potassium tartrate. 4. Mechanical stimulation also induced vomiting in all species. Although the species differed in sensitivity to the different emetic stimulants, the adaptive significance of this interspecific variation is not known. 5. From the stand point of the mechanics for ejecting gastric contents, there is little difference between frogs and mammals. 6. Frogs, particularly Xenopus laevis, may be a useful non-mammalian model for studying emesis.