著者

川勝 正治 手代木 渉 八木橋 元一

出版者

日本生態学会

雑誌

日本生態学会誌 (ISSN:00215007)

巻号頁・発行日

vol.17, no.1, pp.34-41, 1967-02-01

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In this paper, the vertical distribution of freshwater planarians in Hirosaki City, the Mt. Iwaki district (Lat. 40°30′N. to 40°50′N. and Long. 140°15′E. to 140°30′E.) and in the Juniko district (Lat. 40°32′N. to 40°35′N. and Long. 139°56′E. to 140°00′E.), all in the western part of Aomori Prefecture, Honshu, is reported. Mt. Iwaki (altitude, 1625 metres) is an extinct volcano of the Chokai Volcanic Zone and is situated at the south-western corner of the Tsugaru Plain. The Juniko district near the seashore of the Sea of Japan is characterized by many ponds or marshs. The main river systems in the area surveyed are the Iwaki and the Narusawa. The surveys were made in the summer of 1965 and in the spring and summer of 1966. In the area surveyed, five species of freshwater planarians, Dugesia japonica ICHIKAWA et KAWAKATSU, Phagocata vivida (IJIMA et KABURAKI), Phagocata teshirogii ICHIKAWA et KAWAKATSU, Polycelis auriculata IJIMA et KABURAKI and Bdellocephala brunnea IJIMA et KABURAKI, were found. D. japonica and Bd. brunnea were found to be common in many springs in Hirosaki City. Small populations of Ph. vivida and of Ph. teshirogii were also found in some of these springs. In the other districts of the area surveyed, D. japonica, Ph. vivida and Pol. auriculata were widely distributed. D. japonica was found in the stations below the altitude of about 525 metres (inhabitable water temperature range, 9.0〜25.0℃). Ph. vivida was found in the stations within the altitude range from about 40 to 620 metres (5.0〜15.0℃) above sea level. It is however clear that Ph. vivida is the species of nondominance in the western part of Aomori Prefecture. Pol. auriculata was common in the stations within the altitude range from about 200 to 1320 metres (5.0〜14.5℃). The type of the vertical distribution in the area surveyed is shown as J-JV-JVA-VA-A (J : D. japonica ; V : Ph. vivida ; A : Pol. auriculata). The geographical distribution and the breeding of Bd. brunnea were also discussed. According to the best of our knowledge, this species is distributed in Middle and North Honshu (from Kyoto City in the Kinki Region to the Shimokita Peninsula in the northernmost part of the Tohoku Region). In general, their active breeding season was from early February to mid-May. In one breeding period one worm laid one cocoon of 2 to 2.5mm in diametre. The hatching of the cocoons was observed within 23 to 37 days after the laying. In the laboratory cultures, 3 to 12 jveniles were released from one cocooon.