The embryonic development was morphologically observed in hybrid triploid(DT,2n♀×4n♂) and dip-loid loach (DD,2n♀×2n♂) Misgurnus anguillicaudatus. The embryonic development in DD took 35 h 57 min at water temperature of(25±1)℃, while the embryonic development in DT was completed in 36 h 19 min at the same conditions. The embryonic development included six phases cleavage, blastula, gastrula, neurula, organogenesis, and hatching stages. Fertilized eggs in DT( DD) developed into cleavage stage in 40 min (40 min) after fertiliza-tion, blastula stage in 3 h 45 min(3 h 40 min) after fertilization, gastrula stage in 6 h 30 min(6 h 24 min) after fertilization, neurula stage in 9 h 32 min(9 h 20 min) after fertilization, organogenesis stage in 15 h 45 min(15 h 30 min) after fertilization, and hatching in 36 h 19 min(35 h 57 min) after fertilization. The sequence of embryon-ic development in DT was similar to that in DD, though blastula stage in DT was observed later than that in DD. The findings indicate that the hybrid triploid loach have normal embryonic development, providing biological evi-dences of embryonic development for breeding of triploid loach in aquaculture.

Eleven morphometrical items were measured to evaluate the morphological variations in Amur weatherfish Misgurnus mohoity,northern weatherfish Misgurnus bipartitus and oriental weatherfish Misgurnus anguillicaudatus by three methods of multivariate analysis.Cluster analysis showed that northern weatherfish was close to oriental weatherfish,and distantly related to Amur weatherfish in genetic relationship.The principal component analysis revealed that the contributory ratio was 50.430% for the principal component 1,20.880% for the principal component 2 and 10.381% for the principal component 3,with the cumulative contributory ratio of 81.691%.Discriminant analysis showed that three discrimination functions and the discrimination accuracy were 71.4%-100% for P1and 71.4%-100% for P2,the integrative discrimination accuracy being 80.8%.

Intraspecific genetic diversity and intraspecific relationship were analyzed in loach species,Misgurnus mohoity,Misgurnus bipartitus and Misgurnus anguillicaudatus.Five loci were polymorphic in these species and a total 27 alleles were found.The number of alleles per locus ranged from 3 to 7.The loci was highly polymorphic and PIC was 0.526-0.722.Thus,these loach species had high genetic variability.In M.mohoity,M.bipartitus and M.anguillicaudatus,the observed heterozygosity(H0) was 0.978,0.889 and 0.742,and the expected heterozygosity(He) was 0.683,0.781 and 0.721,respectively.The genetic distance of three species of loach was 0.189-0.559.The minimum genetic distance(0.189) was between M.anguillicaudatus and M.bipartitus,which showed two species had a close relationship.The genetic distance between M.anguillicaudatus and M.mohoity was maximum(0.559),which showed they had a distant relationship. Ho and He heterozygosity values showed that 5 microsatellite loci examined didn't deviate from H-W equilibrium.The cluster analysis showed that M.mohoity,M.bipartitus and M.anguillicaudatus were clusteredinto two clades.M.anguillicaudatus and M.bipartitus were clusted,then grouped with M.mohoity.

Nature tetraploid male loaches collected from Hubei Province were crossed with diploid female from Dalian,and all-triploid loach seeds were produced.The results showed that,the average fertilizing rate,hatching rate and survival rate in the cross group(2n ×4n) were 54.69%,80.64% and 56.64%,respectively,and those in the control group(2n ×2n) were 76.23%,82.97% and 79.44%,respectively.The chromosome number of the early embryos of the progeny was 71-75,which could be considered as 100% triploidy.The result of DNA-content flow cytometry on the 6 months old progeny was also conducted to confirm the ploidy status,showing 100% triploidy.The result of the present research showed that the cross between nature tetraploid loaches from Honghu,Hubei and nature diploid loaches from Dalian could produce 100% triploid loaches.This cross method was simple to operate,reliable,and the best way to produce all-triploid loaches.