拉萨裂腹鱼胚胎适宜孵化水温研究

Suitable Water Temperature for Incubating Schizothorax waltoni Eggs

为探索拉萨裂腹鱼(Schizothorax waltoni)胚胎适宜孵化水温,提高胚胎受精率和孵化率,降低初孵仔鱼畸形率,设置5℃、9℃、12℃、14℃、16℃、18℃、20℃、22℃共8个温度梯度进行拉萨裂腹鱼鱼卵孵化实验,统计各温度下的胚胎发育速度、鱼卵受精率和孵化率、初孵仔鱼畸形率及形体指标。结果显示,拉萨裂腹鱼胚胎卵裂期发育最快,到囊胚期、原肠期、器官分化期及出膜期,每个发育时期积累时间逐渐增长;随温度的升高,胚胎发育时间缩短,发育速度加快。各温度条件下,胚胎发育时期与孵化时间均呈幂函数关系,孵化积温随温度升高呈现逐渐降低的趋势。水温9~18℃的鱼卵受精率较高,均超过90%;水温12~16℃的孵化率较高,均超过95%;水温9~16℃的鱼苗畸形率较低,均低于4%。初孵仔鱼全长与孵化温度呈二次多项式函数关系;不同水温的初孵仔鱼体高没有显著性差异,但卵黄囊体积先升高、后降低、再升高。研究表明,适当提高孵化水温能缩短胚胎孵化周期,但水温过高会影响胚胎孵化率,增加初孵仔鱼畸形率,影响仔鱼对营养物质的吸收利用以及器官发育分化。综合考虑胚胎孵化周期、孵化率、初孵仔鱼畸形率及形体指标,拉萨裂腹鱼胚胎适宜孵化水温为12~16℃。

Schizothorax waltoni,the primary economic fish species of Tibet,is distributed only in the Yarlung Zangbo River basin.In recent decades,the S.waltoni resource has been threatened by invasive fish species,hydro⁃power project construction,overfishing and habit degradation and it is urgent to carry out research to support S.waltoni conservation.In this study,we conducted an incubation test of S.Waltoni eggs at 8 water temperatures(5℃,9℃,12℃,14℃,16℃,18℃,20℃,22℃),to study the effect of water temperature on incubation time,fertilization rate,hatching rate,deformity rate and body indices of newly hatched larvae of S.Waltoni and determine the optimal incubation water temperature for embryo development.On April 12th 2019,approximately thirteen thousand fertilized eggs were obtained by artificially induced spawning and fertilization.The eggs were divided into 8 groups and one group was incubated at each water temperature.From fertilized eggs to newly hatched larvae,the development of S.waltoni embryos were observed every two hours,and the pertinent data were recorded for each group.With increasing water temperature,embryo development accelerated and incubation time decreased,while the accumulated incubation temperature gradually decreased.The relationship between the developmental period of S.waltoni embryo(incubation time)was described as a power function of incubation temperature.In the incubation temperature range of 9-18℃,the fertilization rate of eggs exceeded 90%.In the incubation temperature range of 12-16℃,the hatching rate exceeded 95%.In the temperature range of 9-16℃,the deformity rate of newly hatched larvae were less than 4%.The relationship between the total length of the newly hatched larvae and temperature was described by an quadratic function.In the temperature range of 9-22℃,differences in larvae body height were not large,and the yolk sac volume increased initially,then decreased and again increased.The relationship of yolk sac volume and temperature was expressed by a cubic function.In conclusion,increasing the incubation water temperature appropriately can reduce the incubation period.However,a water temperature that is too high adversely affects the hatching rate,the deformity rate,the absorption and utilization of nutrients,organ development and differentiation of the larvae.Considering the hatching cycle,hatching rate,deformity rate and body indices of the newly hatched larvae,the optimal temperature range for hatching S.waltoni embryo is 12-16℃.