Influence of temperature and illumination on egg embryonation and hatching of Salsuginus bermudae from Gambusia affinis

To investigate the effect of temperature and illumination on egg embryonation of Salsuginus bermudae, we collected the eggs of S.bermudae from the gills of Gambusia affinis and put them at temperatures of 35 ℃, 30 ℃, 25 ℃, 20 ℃, 15 ℃ and 10 ℃, exposing to complete illumination, alternation of 12-hour illumination and darkness (light on 06:00; light off 18:00), and complete darkness, and then recorded the hatchability and the time needed for larva hatching. The results show that the optimum incubation temperature was 35℃, and the correlation between the hatching rate and incubation temperature was significantly positive. Besides, temperature influenced the embryonation period obviously: coracidium appeared on the 2^nd day after the eggs being laid at 35 ℃, but the larvae only appeared on the 7^th day after the eggs being laid at 10 ℃. Effect of different illumination conditions on the hatching rate was not remarkable, indicating that light is not a necessary factor for egg hatching, but 12-hour illumination and darkness can delay the embryonic period.