Abstract: The growth of marine organisms is currently challenged by multiple environmental stressors. The early life stages of sea urchin Strongylocentrotus intermedius are sensitive to environmental changes. Temperature and salinity are important environmental factors affecting the growth and development of marine animals. To understand the temperature and salinity tolerance of the early embryonic development of sea urchin and its optimal environmental conditions, we used the central composite design (CCD) and response surface methodology (RSM) to investigate the interactive effects of temperature (12-26 ℃) and salinity (22-34) on the early development of the sea urchin embryo. The quantitative relationship models between temperature, salinity and the fertilization rate, floating rate and metamorphosis rate of sea urchin embryos were established, and the best combination of temperature and salinity was obtained through statistical optimization methods. The results showed that both high and low temperature and salinity were not conducive to the early embryonic development rate of sea urchins. The effect of temperature on the early embryonic development of S intermedius was greater than that of salinity, with certain antagonism between temperature and salinity. The primary effects of temperature and salinity, and the secondary effects of temperature significantly affected the fertilization rate, floating rate, and metamorphosis rate of the S. intermedius embryos (P<0.01). The interactive effects of temperature and salinity significantly affected the embryo fertilization rate and metamorphosis rate of S. intermedius (P<0.05), but did not affect the floating rate. The secondary effect of salinity significantly (P<0.01) affected the fertilization rate of the S. intermedius embryos, but did not affect the floating rate and metamorphic rate. The determination coefficients of the fertilization rate, floating rate and metamorphosis rate were 0.9736, 0.9946, and 0.9925, respectively, indicating that the models were effective and could be used to predict the fertilization rate, floating rate and metamorphosis rate of S. intermedius. The model optimization and verification tests showed that, at 17.71 ℃ and salinity of 31.85, the fertilization rate, floating rate and metamorphosis rate reached the maximum value, with a satisfaction rate of 0.969. Our findings can provide theoretical basis for the artificial breeding of sea urchin.

Key words: sea urchin Strongylocentrotus intermedius, embryonic development rate, temperature, salinity, interactive effect.