Heterozygous genetically uniform clones allow for comparison of the same genotype over time and under different ambient conditions. This allows us to estimate genetic correlations and detect genotype-by-environment interactions and phenotypic plasticity for complex traits such as sex and gonadal differentiationheterozygous Japanese flounder clone was produced by from male and female mitotic gynogenetic diploid parents at Beidaihe Central Experiment Station, Chinese Academy of Fishery Sciences, Qinhuangdao, Hebei Province. The fish were cultivated in six gradient temperatures to observe the effects of temperature on sex differentiation, sex ratio, and growth. The results provide basic data on clonal biology and breeding. The experimental fish were reared separately at 16, and 31 from 35–110 dph (days post hatching). In the meantime, 10 fish were sampled every 5 days from 35–80 dph, then every 10 days after 80 dph. Growth data, including total length and body weight were measured, and samples were preserved in Bouin’s fluid for paraffin sectioning and histological observation. The results revealed that the Japanese flounder larvae reared in , began to differentiate when grew to 60 dph. Larvae 70 and 90 dph started to differentiate at 19 . However, no sex differentiation was observed at 31 even after 110 days. Histological observations revealed that all of the heterozygous clones from the different water temperatures were female, which suggested that high water temperature does not affect female sex reversal. The initial trends in morphological growth included a gradual increase in total length and weight with increasing temperature, except at 31 reared larvae grew faster than those reared at 28 after 55 dph, and was the fastest growing group overall. In summary, sex differentiation of heterozygous Japanese flounder clones quickened with increasing temperature. Temperature had no effect on sex ratio, all temperature groups were female. Furthermore, the larvae kept at 25