イボニシPurpura clavigera (KÜSTER) の吸着力に及ぼす温度並に鹹度の影響

Abstract

Some tests have been done on the adhesive force of Purpura clavigera, ?? representative of oysetr enemy in Japan, under the purpose to find out available method exterminating oyster drills from seed oyster in various conditions of environmental elements, viz, salinity and temperature. At experiment, an empty shell of abalone with the drills attached tenaciously was hung down vertically in those media given below in still condition for two minutes, and the percentage of drills fallen off was enumerated. Lower salinity media were prepared by diluting sea water with fresh water at the rate of a quarter, two-fourths and three-fourths, respectively. Higher salinity ones were made in a manner adding 20, 40, 60, 80 and 100 grams of common salt per litre of sea water. Water temperature on which the experiments for thermal effect was undertaken ranged within a limit from 3.7° to 53.3°C. The following matters may be mentioned as the results taken from the experiments dealt with herein. The adhesive force of the drill appears to be weak against higher salinity and temperature. But it appears to stand against lower salinity and temperature. The adhesive property of the drill shows a broad range of adaptability for temperature, especially for lower one as holding adhesive force within ?? limit from 3.7° to 17.0°C. Lastly it should be writen in this place that the drill fallen off is hundred per cent in the annexed cases: 80g./L. salt (30.3°C), 100g./L. salt (29.9°C., 14.7°C.), and temperatures above 36.5°C.