イボニシにおける imposex の地方変異

抄録

The Neogastropoda had been recognized as dioecious having the penis in the male but no penis in the female. Since early 1970s, however, many species have been found showing the phenomenon of "imposex" in which male characters such as the penis and vas deferens are superimposed on the female. Nakano and Nagoshi (1980) found the same phenomenon in Thais clavigera collected in Shima peninsula from 1976 to 1978. Therefore, in order to infer the cause of this phenomenon, we investigated the local variation in the frequency and intensity of imposex in the females of T. clavigera collected at 9 localities of Japan, i.e., Asamushi, Oga, Yokosuka, Shimoda, Toba, Shirahama, Hiroshima, Amakusa and Kagoshima, from 1978 to 1980 and at Hong Kong in 1982. As a result, the imposex was found in all localities of Japan with various frequency and intensity but not in Hong Kong. The imposex has been confirmed by many researches since early 1980s to be induced by tributyltin (TBT) contamination from antifouling paints used for ships and boats. Therefore, the results of the present study suggest that coastal waters in many localities of Japan had already been contaminated with tributyltin from antifouling paints about 10 years ago.