津軽半島の淡水産プラナリアの生態調査報告

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The vertical distribution of freshwater planarians in the Tsugaru Peninsula in Aomori Prefecture (Lat. 40°40′N. to lat. 41°20′N. and Long, 140°10′E. to Long. 140°45′E.), the northernmost part of Honshu, was surveyed in 1966 and 1967. The Peninsula faces both the Tsugaru Straits and Mutsu Bay. The larger part of the Peninsula is covered with low mountains, of which the highest peak is 827 metres in height. The south-western part of the Peninsula is characterized by a level plain of cultivation. The main river system in the area surveyed is the Iwaki, which discharges into Juni-ko Lake and the Sea of Japan. In the area surveyed, six species of freshwater planarians, Dugesia japonica ICHIKAWA et KAWAKATSU, Phagocata vivida (IJIMA et KABURAKI), Phagocata teshirogii ICHIKAWA et KAWAKATSU, Polycelis auriculata IJIMA et KABURAKI, Polycelis sapporo (IJIMA et KABURAKI) and Dendrocoelopsis lacteus ICHIKAWA et OKUGAWA, were found. D. japonica was found to be common at the stations below the altitude of about 160 metres (inhabitable water temperature range, 8.0〜22.2℃). Ph. vivida was common at the stations below the altitude of about 380 metres (5.0〜21.8.C). Pol. auriculata was found in both the cold-water mountain streams and in some cold-water springs in the seaward district (0.5〜480m, 9.0〜14.0℃). Pol. sapporo, one of the common species in Hokkaido, was found at the stations below the altitude of about 120 metres (9.0〜21.8℃). It is an interesting fact that this species was rather common at the stations in the Tappizaki Cape district in the Tsugaru Peninsula. Small populations of Ph. teshirogii and Den. lacteus were found in the Tsugaru Peninsula. The type of the vertical distribution of the planarians in the area surveyed is (JSV)-JSVA-SVA-VA-A (J : D. japonica ; V : Ph. vivida ; S : Pol. sapporo ; A : Pol. auriculata). The geographical distribution of Pol. sapporo and Den. lacteus in Honshu were discussed. According to the best of our knowledge, Pol. sapporo has been recorded only from the northern side of the demarcation line drawn between the base of the Shimokita Peninsula and of the Tsugaru Peninsula (cf. KAWAKATSU 1965,p. 356,Fig. 5,1967,p. 125,Fig. 5). Den. lacteus has been recorded both from the Tsugaru Peninsula and in a little south of the southern demarcation line of distribution of Pol. sapporo (cf. KAWAKATSU, TESHIROGI, ISHIOKA & KASAHARA 1968).
1969-04-01

津軽半島の淡水産プラナリアの生態調査報告

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