著者

北川 哲郎 小田 優花 細谷 和海

出版者

近畿大学農学部

雑誌

近畿大学農学部紀要 = Memoirs of the Faculty of Agriculture of Kinki University (ISSN:04538889)

巻号頁・発行日

vol.46, pp.31-36, 2013-03-01

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[Synopsis] The paradise fish, Macropodus opercularis is distributed from the northern part of Vietnam to the Ryukyu Archipelago, and categorized as an endangered species in Japan. The endemism of the Okinawan population was not proven, even though Okinawa is isolated from the mainland of East and Southeast Asia. Furthermore, the ecological information was not fully investigated and the quantities are not sufficient enough to protect it. To elucidate the local variation in paradise fish, reproductive characteristics of the Okinawan fish population were examined in the laboratory. During the trials, a pair of broodstock were reared under constant environments (25 ± 0.5 °C , 14 h L - 10 h D). Each reproductive behavior was observed once per four to ten days at least. The number of the fertilized eggs was counted as being 319 - 581. Hatching was observed two days later, and then the larvae proceeded to feed six days after hatching. The newly hatched larvae drifted beneath the water surface, or fell down on the bottom of the tank. The fertilized eggs were large, and buoyancy was tenuous, if compared with the case of typical M opercularis from the mainland China. The egg-mass after spawning and prelarvae under a bubble nest were guarded by a single male parent. Protective behavior was also found in females. However, female was often attacked by the male if they were mistakenly perceived as enemy by himself. In this experiment, the filial cannibalism was not observed as far as each broodstock is concerned.