Tolerance of Huso dauricus embryo at its different development stages to low temperature
研究了达氏鳇12个发育期胚胎经过不同低温（2 ℃、3 ℃、5 ℃、7 ℃和8 ℃）处理12 h、24 h、2 d、3 d、6 d、10 d、15 d、20 d和30 d后的孵化率和仔鱼成活率.结果表明，卵黄栓期、隙状胚孔期、神经管闭合期胚胎在2～8 ℃水温下，处理24 h后孵化率为0；卵裂期、囊胚早期、原肠中期胚胎在2～8 ℃水温下，处理3 d后孵化率低于30%；囊胚晚期、原肠早期、眼基期、尾芽期、心跳期和尾达头部期胚胎在5～8 ℃水温下，处理3 d后孵化率、仔鱼成活率超过70%；随低温处理时间延长，胚胎和仔鱼的死亡率增加，处理时间与孵化率、仔鱼成活率呈负相关；囊胚晚期、原肠早期、眼基期胚胎在5 ℃水温下耐受力较强，处理10 d后孵化率、仔鱼成活率超过70%.本研究表明，达氏鳇胚胎发育过程中囊胚晚期、原肠早期和眼基期胚胎可以在某一低温下进行短期保存，其孵化率、仔鱼成活率与常温（16～17 ℃）下没有显著差异.这对于达氏鳇胚胎（受精卵）的长途运输有重要意义.
This paper studied the embryo hatching rate and larva survival rate of Huso dauricus when the embryo at its different development stages was exposed to low temperature for different durations.The results showed that the embryo at its yolk plug,narrow-opening,and neural block closing stages could not survive at 2～8 ℃ over 24 h.When exposed to 2～8 ℃ for 3 days,the hatching rate of embryo at its cleavage,early blastula,and mid gastrula stages was lower than 30%.Both the embryo hatching rate and the larva survival rate were higher than 70% when the embryo at its late blastula,early blastula,optic rudiment,tail bud,heart beating,and tail touching head stages was exposed to 5～8 ℃ for 3 days.The death rates of embryo and larva under low temperature were increased with time.There was a negative correlation between the exposure duration at low temperature and the embryo hatching rate (r=-0.8024) and larva survival rate (r=-0.8468) of H.dauricus.The embryo at its late blastula,early gastrula,and optic rudiment stages had a stronger tolerance at 5 ℃ for 10 h,with the embryo hatching rate and larva survival rate being higher than 70%.It could be concluded that there was a little difference in embryo hatching rate and larva survival rate of H.dauricus when the embryo at its some development stages was preserved at low temperatures at least for 10～15 days and at normal temperature (16～17 ℃).
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