Grant-in-Aid for international Scientific Research
|Allocation Type||Single-year Grants|
|Research Institution||KYOTO UNIVERSITY|
HORI Michio Graduate School of Science, Kyoto University, 大学院・理学研究科, 教授 (40112552)
MWAPE L.M Lake Tanganyika Research Unit, Department of Fisheries of Zambia, タンガニイカ湖支所, 所長
MUDENDA H.G Department of Fisheries of Zambia, 中央研究所, 所長
KIMURA Seishi Faculty of Bioresources, Mie University, 生物資源学部, 助教授 (00115700)
KONDO Takaki Division of Natural Science, Osaka Kyoiku University, 教育学部, 助手 (50116159)
YAMAOKA Kosaku Usa Marine Biological Institute, Kochi University, 海洋生物教育研究センター, 教授 (20200587)
KOHDA Masanori Faculty of Science, Osaka City University, 理学部, 講師 (70192052)
YANAGISAWA Yasunobu Faculty of Science, Ehime University, 理学部, 助教授 (90116989)
バソンジ G. タンザニア水産研究所, 所長
ムワッペ L. ザンビア水産庁, タンガニイカ支所, 所長
ムバンバ M. ザンビア水産庁, 中央研究所, 所長
須之部 友基 千葉県立中央博物館, 主任技師 (00250142)
桑村 哲生 中京大学, 教養部, 教授 (00139974)
|Project Period (FY)
1995 – 1996
Completed(Fiscal Year 1996)
|Budget Amount *help
¥22,000,000 (Direct Cost : ¥22,000,000)
Fiscal Year 1996 : ¥10,800,000 (Direct Cost : ¥10,800,000)
Fiscal Year 1995 : ¥11,200,000 (Direct Cost : ¥11,200,000)
|Keywords||Lake Tanganyika / Cichlid / Fish community / Polymorphism / Scale-eater / Laterality / Interspecific interaction / Community structure / Frequency dependent Selection / 群集の安定性 / 群集の多様性 / 多様性維持機種|
Lake Tanganyika is one of the most speciose freshwater systems in the world. Diversity of fishes is highest on rocky littoral habitats in the lake, and the fish communities there are mainly composed of cichlids allied to each other to various degrees.
In 1995 and 1996, our Japanese and Zambian cooperative team conducted the ecological researches on the fish communities in order to clarify the factors responsible for the exceptionally high diversity in the lake. The researches have revealed the direct and indirect interactions among fishes together with an marvelous variety of their breeding and feeding habits. Such variety of interactions and habits must be indispensable factors for maintaining the biodiversity in the littoral zone of the lake.
The most important finding is that the handedness of scale-eater is determined on the basis of simple genetics and that the abundance of individuals with left- or right-handedness depends on frequency-dependent natural selection. Within a given population where one species of scale eater occurred alone, the frequency of the two phenotypes oscillated around unity. This phenomenon was effected through frequency-dependent selection exerted by the prey's alertness. Thus, individuals of the rare phenotype had more success as predator than those of the more common phenotype.
Where two species of scale eaters cohabited, the ratio altered gradually in a manner of one phenotype being majority to minority depending to the fish size. And the alternation pattern of both species coincided with each other. These results strongly suggest that the ratios of handedness of the two species oscillate synchronously, or at least fluctuate periodically along with each other. The phenomenon may be caused through the prey's guarding against the majority phenotype irrespective of scale eater species. The phenomenon and the mechanism may be an important factor which maintains the species diversity in the fish communities.