| The eggs of the darkbarbel catfish were fertilized artificially at 23℃, from the parental fish collected in the Jialing River from May, 2003 to June, 2004. The embryonic development was observed at nine experimental temperatures, i.e. eight constant temperatures (17, 19, 21, 23, 25, 27, 29 and 31 ℃ ) and a varying temperature (blastodem-blasrula stage at 23 ℃ , gastrulae-neural plate stage i at 25 ℃ ,organogenesis-hatching stage at 27℃). The results showed that the total hatching rate, totalincubation duration and survival rate in each developmental stage changed significantly withchanging temperature. The total hatching rate increased with temperature increasing from 17 to 25℃, then decreased with it increasing from 25 to 31℃. The total hatching rate at 25℃ showed highest (76.92±1.07%). Comparison of survival rates in different developmental stages among different constant temperatures indicated that the highest survival rates in the three stages of blastodem-blastula, gastrulae-neural plate and organogenesis-hatching were obtained at 23, 25 and 27℃, respectively. The total hatching rate (93.69±0.57%) with the varying temperature regime was significantly higher than those at each constant temperature, while its total incubation duration and accumulated temperature were close to those at the constant 25 ℃. Analysis of the results showed that the embryos could deyelop adequately with temperature of 21-29℃ and develop optimally at 25 ℃ in constant temperature regime. Discussion in this paper suggested that different embryonic stage might adapt to different temperature. The firstly improvement on the total hatching rate by temperature increasing gradually, subsequently decrement by temperature increasing sequentially in this study... |
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