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Title: 宮入貝卵子の発育と孵化に関する研究
Other Titles: An Observation on Growth and Hatching of Oncomelania Eggs under Certain Laboratory Conditions
Authors: 野島, 尚武
Authors (alternative): Nojima, Hisatake
Issue Date: 31-Mar-1973
Publisher: 長崎大学熱帯医学研究所 / Institute of Tropical Medicine, Nagasaki University
Citation: 熱帯医学 Tropical medicine 15(1). p23-35, 1973
Abstract: The present study has been undertaken to find the most efficient procedure and inost optimal conditions for obtaining a large number of young Oncomelania snails in the laboratory for experimental purpose. In this study the author attempted to obtain detailed information about the influence of some environmental physical factors on growth and hatching of the eggs. Initially, the response of the eggs to temperature and degree of wetness was observed. Fresh eggs of O. nosophora and O. quadrasi which were covered with mud-like particles were collected from the egg-laying chambers at daily intervals and placed on soil or filter paper contained in Petri dishes which were kept at constant temperature and moisture. If conditions were proper, the egg-cells developed up to mature larvae and some of them hatched normally in these culture chambers. For testing the influence of wetness, the six grades of wetness were experimentally established according to amount of water contained in filter paper of 15cm diameter. On dry soil and dry filter paper, the eggs died within several hours. In O. nosophora eggs, desirable amount of water given to filter paper was around 6ml at least, but O. quadrasi eggs required much larger amount of water for the survival and development. Under desirable wetness conditions, optimal growth was found at about 20-25℃ in which about 80 per cent or more of the eggs developed to the mature stage (the stage of late veliger) within 20 days. Higher temperature over 30℃ resulted increased mortality in the early stage of development. At 15℃, on the other hand, the eggs required a longer period of incubation for maturation, especially O. quadrasi eggs markedly inhibited in the development. On further lowering of temperature below 10℃ they almost ceased their growth. In culture chamber, the eggs began to hatch naturally 20 to 30 days after incubation under ideal conditions, but the rate of hatching was not especially high. If the culture ground and filter paper were covered with water at this time, mature eggs actively hatched within 24 hours. On the other hand, when the fresh eggs were cultivated on filter paper submerged into water from begining, most of eggs developed to mature eggs and hatched successively day by day. According to the observation based on these phenomena, the incubation period necessary to obtain maximum hatching was recognized to be about 22 days at 20℃, 15 days at 25℃ and 13 days at 27-30℃ respectively. Therefore, this procedure can be recommended as an efficient way to obtain young snails. / 著者は宮入貝O. nosophora, O. quadrasi卵子の発育孵化に及ぼす物理的条件,特に温度と水分量の影響について実験的観察を行い次の結果を得た.1)久留米で採集された宮入貝からみると,自然界に於けるO. nosophoraの産卵の時期は主として4, 5, 6月にあり,7月に入ると終熄するものが多い.2)宮入貝の成熟には一定量以上の培地の水分が必要である.一般にO. nosophoraは比較的水分不足に強いが,O. quadrasiは少くとも水浸しの状態以上の水分が必要である.3)最適の温度は両種とも概ね20℃乃至25℃附近にあり,概ね20日前後に大部分が成熟卵子に発育する.32℃以上,10℃以下ではその途上に死滅又は発育を停止する.特に発育初期に於いてその影響が強い.4)成熟卵子に発育した時期に飼育培地に冠水すると,一挙に多数の稚具を得ることができる。5)初めから水中に漬けた濾紙上で飼育すると,卵子は順調に発育,遂次孵化し,高率に稚具を得ることができる。6)培地で卵子が孵化するまでに要する飼育期間は温度により異なるが,25℃で概ね15日である.7)冠水処理及び,浸水濾紙飼育は実験室内で,多数の稚貝を得る方法として推奨出きる.稿を終るに当り,御指導と御校閲を載きました恩師片峰大助教授に深甚の謝意を表します.貝採集にあたって御協力載きました久留米大学岡部浩洋教授をはじめ,熱研寄生虫学教室の諸兄に感謝致します.尚.本研究は文部省科学研究費及び日米医学協力会議の補助を受けた.
URI: http://hdl.handle.net/10069/4130
ISSN: 03855643
Type: Departmental Bulletin Paper
Appears in Collections:Volume 15, No. 1

Citable URI : http://hdl.handle.net/10069/4130

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