Grey face moray Siderea thyrsoidea could spawn naturally in the aquarium. The natural spawning was found to occur at night. The brooder guarded the stacked eggs in the center of the circled body, as like the snake. Eggs are spherical, translucent, and demersal at the salinity of 32 ppt. Compared with Japanese eel Anguilla japonica the egg of grey face moray is larger, with a mean diameter of 3.44 mm but without oil droplet. At the water temperature of 26-27 ℃ and salinity of 32 ppt, the fertilized eggs were hatched at about 112 hours after spawning. The mean total length of newly hatched pro-larvae is 11 mm, having a pair of big eye. The pigment of eye and pectoral fin appeared at 6 hours after hatching. The eye pigmented significantly at 20 hours after hatching. The pro-larvae had thin foreguts, long and broad midguts, and short hindguts. In aquaria, the larvae usually sink down to the bottom, and swum by sinuate posture intermittently. The mean total length of 2 day-old pro-larvae is 11.5 mm, and the pectoral fins had formed. Meanwhile, the forward mouth and fang-like teeth were formed, but without actions of opening and closure. The 3 day-old pro-larvae were transparent. The sinuate swimming posture lasted longer than it did before. On the 7-day, the pro-larvae were weak and sunk on the bottom. On the 8-day old, the pro-larvae all died.
Key words: Siderea thyrsoidea, Breeding behavior, Development of pro-larvae