Embryonic development and morphologic observations of newly-hatched Rhinogobio nasutus Larvae
[Objective]The aim of this study was to establish large-scale artificial breeding technology and provide a scientific basis for the establishment of productive seedling and the protection of germplasm resources for Rhinogobio nasutus.[Method]Fertilized eggs of Rhinogobio nasutus were obtained through artificially-induced spawning,and the morphological characteristics of embryo and larval development were recorded and analyzed at a constant water temperature of(23.2±1.0)℃.[Result]The unfertilized mature eggs were spherical,light green,and drifting,with a diameter of(0.60±0.08)mm.After fertilization and hy-dration,the fully swollen eggs became translucent,with a diameter of(0.76±0.08)mm.Under the condi-tions of water temperature(23.2±1.0)℃ and pH 8.71～8.86,the fertilized eggs developed into the blas-tula stage in 3.67 hours,the gastrula stage in 5.95 hours,embryo body formation in 9.55 hours,organ for-mation in 13.38 hours,muscle effect in 19.98 hours,and heartbeat in 24.05 hours.After 40.43 hours,em-bryo development was completed,and the larval stage was reached.The overall length of newly hatched lar-vae ranged from about 3.00 to 4.00 mm,with a heartbeat of 101～132 beats per minute.The yolk of the lar-vae was completely absorbed within 2 days,and in some larvae,the cloaca was opened.All larvae started in-gestion 3 days after hatching,under the condition of a water temperature of 26℃.[Conclusion]This study recorded,analyzed,and described the process of embryonic development of the big-nosed minnow using arti-ficial labor induction.Hatching larvae of Rhinogobio nasutus were successfully obtained.The embryonic de-velopment process went through seven stages,including the embryo dish stage,cleavage stage,blastocyst stage,gastrula stage,neuroembryonic stage,organ formation stage,and hatching out of the membrane.Each development stage consisted of several phases.
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