秋吉及び三瓶山地方の淡水産プラナリアの生態調査報告

抄録

In the present paper, a description is given of the distribution of the freshwater planarians in the Akiyoshi, Omijima Island in the Sea of Japan (Yamaguchi Pref.) and Mt. Sambe (Shimane Pref.) districts in southwest Japan. The Akiyoshi district is characterized by the development of a Karst, so-called Akiyoshi-dai (Akiyoshi limestone plateau), which is about 200 to 400 metres above sea level. There are many limestone caves in this district (the largest one, Akiyoshi-do Cave…also spelled Shuho-do Cave, is located at the southern foot of the Akiyoshi-dai ; cf. KAWAKATSU 1960). The area surveyed is situated in Lat. 34°00′N. to 34°30′N. and Long. 131°00′E. to 131°11′E. The surveys were made in February, March, April and August, 1965. Mt. Sambe, an extinct volcano, is 1126 metres in height and is situated in Lat. 35°08′N. and Long. 132°37′E. The survey of the volcano was made in April, 1958. In these districts, the two species of freshwater planarians, Dugesia japonica ICHIKAWA et KAWAKATSU and Phagocata vivida (IJIMA et KABURAKI), were found. D. japonica, the commonest flatworm in Japan, was found in the rivers, creeks, brooks, brooklets and springs both in the plains and lower mountain districts. This species was also found in many underground streams and pools in the caves. Ph. vivida is rather common in the cold-water biotopes, such as small springs, outlets of caves and pools in some caves. It is an interesting fact that Ph. vivida is very rare in mountain or hill streams in the Akiyoshi district ; this species is found commonly in the cold-water mountain streams in Central and North Japan. The inhabitable water temperature range of D. japonica and Ph. vivida in the Akiyoshi and Mt. Sambe districts is as follows : D. japonica (4.3〜27.0℃) ; Ph. vivida (4.0〜21.5℃). The type of vertical distribution in these districts is J-JV (J : D. japonica ; V : Ph. vivida). The new records on the distribution of the freshwater planarians in southwest Japan is also described. Phagocata kawakatsui OKUGAWA is evidently common in the vicinity of Takamatsu City, Kagawa Prefecture in Shikoku (type locality : Minoda, Asahi-cho in Kameoka City in Kyoto Pref. ; also found at Saga-tenryuji-cho in Kyoto City and in Matsumoto City in Nagano Pref. in Central Japan).