Diploid (D) and tetraploid (T) loach (M.anguillicaudatus),large scale loach (P.dabryanus) (P) and their reciprocal hybrids were produced by artificial fertilization.Nine genetic crosses were made.These were (♀×♂):D×D,D×T,D×P,T×D,T×T,T×P,P×D,P×T and P×P.The relative DNA contents of the progenies were examined by flow cytometry.The results showed that D×D,D×P,P×D and P×P were diploid,D×T,T×D,P×T and T×P were triploid,T×T were tetraploid.The ratio of relative DNA contents of the three types was about 2∶3∶4.The karyotypes of the progenies were analyzed and compared by the PHA colchicine hypotonic-air drying technique.D×D has 2n=50 chromosomes,consisting of 8 metacentrics (m),6 submetacentrics (sm) and 36 telocentrics (t) chromosomes.P×P has 2n=48 chromosomes,consisting of 12 m,4 sm and 32 t.Both species have a fundamental arm number (NF) of 64.T×T has 4n=100 chromosomes,consisting of 16m,12sm,72t,NF=128.D×P and P×D are 2n=49,10m+5sm+34t,NF=64; D×T and T×D are 2n=75,12m+9sm+54t,NF=96; T×P and P×T are 2n=74,14m+8sm+52t,NF=96.By comparative analysis,the karyotypes of diploid and triploid hybrids are intermediate between the parental species,consisting of a haploid maternal set and a haploid paternal set. 