日本の陸水ヱビ類の生態 : 1.ヌマエビCaridina japonicaについて
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概要
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1)The Atyid shrimp of soutern Japan, C. japonica, as commonly known by the name "Taniebi", meaning 'the shrimp of the mountain stream' in Kii Provinces, excepting some specimens which have probably been carried down the river by the flood, dwells in the mountain stream, and lives on the small organic substances. 2)In the habitaion where Tani-ebi and Nuka-ebi (Paratya compressa) dwell, the former segregates in the upper part including the vicinity of the stream and the latter from the lower part to the rever, but in the boundary both co-exist. The processes that induce such habitat segregation as this will be concerned with their crawling actions upwards the stream and physiological requirements for peculiar physical enviromental conditions. 3) All the time, the shrimps (Tani-ebi) hide themselves under the rocks and stones, but every evening they swarm outside of their hiding places and seek for their food. But few of them do so even in the morning and sometimes in the cloudy daytime. These modes of daily periodic behavior resemble those of a river snail which have been reported by MORI ('48), and seem to be maintained by the combined actions of solar illumination and water temperature. 4) According to the results of the author's examination of 143 specimens caught from Yaso-tani, Kii, it may be generally said that in late July, the population of Tani-ebi divides into three groups by body-length: A group measuring 30mm level, B group over 20mm and C group 19〜22mm. Besides there will be the hatched larvae. The male is 10mm smaller than the female in adult, therefore the males of A group appear to the menbers of B group. The smallest one among the berried shrimps dealt with is 25mm long. It is likely that the spawning season for this shrimp extends from spring to autumn, and that two months, June and September are the height of it. 5)C. japonica sikokuensis has been separated from the typical species by KUBO ('28), i. e., characterized morphologically by the very short and greatly bended rostum and ecologically by living in the limestone cave, Ryugado. But the typical can be collected in the inside and outside water of the cave and sometimes flows into there from the neighbouring mountain stream by the flood. Therefore it is clear that this subspecies must be an abnormal form of the typical species that has stayed in the cave.
- 1956-12-15