日高地方の淡水産プラナリアの生態調査報告

抄録

KAWAKATSU, Masaharu (Biol. Lab., Fuji Women's Coll., Sapporo) Report on the ecological survey of freshwater planarians in the Hidaka district, Hokkaido. Jap. J. Ecol. 15,173-183 (1965). In this paper, the vertical distribution of freshwater planarians in the Hidaka district in South Hokkaido is reported. Most of the district is covered with mountains. The Hidaka Mountains, the backbone of South Hokkaido, are situated in Lat. 41°50′N. to 43°10′N. and Long. 142°30′E. to 143°20′E., the highest peak, Mt. Poroshiri-dake (2052 m above sea level), is at the northern corner of the mountain-chain. Topographical evidence of the Pleistocene glaciation has been found on the summits of the mountains. The area consists largely of plutonic and metamorphic rocks. The southern part of the Hidaka Mountains consists of two topographical units, one is the lower mountainous land (the main peak, Mt. Apoi, is 810 m high) and the other is the flatsurfaced hilly land (the Erimo Cape district). The Hidaka district has a rigorous climate. The average temperature of the year is about 6° to 7℃ and the rainfall amounts to about 1000mm at the foot of the mountains or at the seashore districts (cf. Table 1). Surveys were made on the rivers, creeks, brooks, brooklets and springs of the mountain and seashore districts in August of 1958,1961 and 1962. In the area surveyed in the Hidaka district, six species of freshwater planarians, Phagocata vivida (IJIMA et KABURAKI), Phagocata tenella ICHIKAWA et KAWATATSU, Polycelis sapporo (IJIMA et KABURAKI), Polycelis auriculata IJIMA et KABURAKI, Polycelis akkeshi ICHIKAWA et KAWAKATSU and Dendrocoelopsis lacteus ICHIKAWA et OKUGAWA, were found. In the Hidaka district, two other species of planarians, Dugesia japonica ICHIKAWA et KAWAKATSU and Dendrocoelopsis ezensis ICHIKAWA et OKUGAWA, were collected by Prof. A. ICHIKAWA and Dr. T. KAWAI. D. japonica is one of the most common freshwater planarians in the Japanese Islands. In the Hidaka district, however, this species was collected only in the brooks flowing through the seashore district (Hidaka-Mitsuishi) and the plain (Obihiro City and Otofuke River). Ph. vivida was rather common in the creeks, brooks and brooklets within the altitude range from the level of the seashore to about 1200 metres above. Ph. tenella, which may be a subterranean inhabitant, was found only in the pools of swampy land and in the spring-fed brooklets in the Mt. Apoi district. This species was found in the stations below the altitude of about 580 metres. Pol. auriculata was common in the creeks, brooks, brooklets and springs in the altitude range from about 90 to 1700 metres or more. Pol. sapporo was found everywhere in the rivers, creeks, brooks and brooklets both in the seashore district and the stations below the altitude of about 800 metres. Pol. akkeshi was found only in the brooklets in the Mt. Apoi district. Den. lacteus was found only in the brooklets in the Mt. Apoi district (st. 54 and st. 55). Den. ezensis was collected only in the brooklets in Obihiro City. The inhabitable water temperature ranges of the above mentioned species of freshwater planarians which were found in the Hidaka district are as follows : Ph. vivida (5.8〜11.8℃) ; Ph. tenella (12.1〜20.9℃) ; Pol. auriculata (10.5〜13.5℃) ; Pol. sapporo (6.8〜20.9℃) ; Pol. akkeshi (12.8〜20.9℃?) ; Den. lacteus (17.8〜18.2℃). Two or three of the above mentioned species were found together where their inhabitable water temperature overlapped. The type of vertical distribution in the Hidaka district is JSV-SVA-VA-A (J : D. japonica ; V : Ph. vivida ; A : Pol. auriculata ; S : Pol. sapporo).