THE MOUTH OPENING REACTION OF ONCOMELANIA AND ITS COMPARATIVE STUDY WITH ONCOMELANIA NOSOPHORA AND O. HUPENSIS : STUDY OF THE FOOD HABIT OF ONCOMELANIA II

Abstract

As reported in a previous paper the movement of a buccal mass of Oncomelania could be utilized for the examination of its food habits. This movement was named as an"mouth opening reaction of Oncomelania"and a study was carried out on conditions under which this reaction could be smoothly repeated in a certain time unit. The result was as follows. 1. To gain a good result the examination of this reaction should be undertaken with snails in hunger state, and during the time of experiment its body surface, particularly that of its mouth part should be covered sufficiently with a film of water. In ordinary cases such a state will continue to about ten minutes after the commencement of the examination. 2. For the examination of this reaction the optimum PH range is about 5-8.5. In the temperature range of 18-30℃ it can be safely carried out. Within the temperature range of 20-25℃, however, a more suitable result could be obtained. Humidity of air gives no effect on this reaction provided that sufficient water film covers the surface of the snail body. 3. No marked difference was found between the reaction of O. nosophora and that of O. hupensis when both were feeded with soils of the habitat, rice powder and water only. The result suggests that the food habit of both species of snails would be closely related. 4. The frequency of this reaction in a definite time unit was found to be larger with younger snails as compared with that of older ones, which suggests that the intrinsic stimulus for this reaction would be Iarger in the former.