Abstract: 【Objective】 To investigate the ability of 1-phenyl 2-thiourea (PTU) to inhibit melanogenesis in flk1 zebrafish

and to explore the optimal concentration of PTU for generating transparent zebrafish without affecting their growth and development.【Methods】 Zebrafish embryos at 24 hpf (hours post fertilization) were incubated with 0.0125-1.0 mmol/L PTU for some time. Then at designated time points

the effects of PTU with different concentrations on the melanogenesis

the growth and development of zebrafish embryos were evaluated through the changes in melanin area

the morphology and physiology at 80 hpf including the mortality

hatching rate

heart rate and SV-BA distance of zebrafish embryos. 【Results】 With increasing concentrations of PTU

the inhibition on melanogenesis enhances with an increase in the toxicity

which is characterized by the increased mortality and SV-BA distance

the reduced hatching rate and heart rate

0.0125-0.025 mmol/L PTU has no impact on zebrafish

and PTU at a concentration higher than 0.05 mmol/L can completely suppress melanogenesis in zebrafish. When treated with 0.025 mmol/L of PTU

the detection of zebrafish vessel was not affected by generated melanin. And 0.05 mmol/L of PTU has little impact on the heart rate and SV-BA distance of zebrafish. 【Conclusion】 For flk1 zebrafish experiment

before 72 hpf

the concentration of PTU is suggested to be less than 0.05 mmol/L. And then in this concentration range

such a PTU concentration is optimal

that is the melanogenesis does not affect the viviperception and signal detection required by a specific experiment

while the influence on the development and growth of zebrafish is minimum.