Influence of feeding frequency and light on the growth of ephyra of jellyfish (Rhopilema esculenta)

Abstract:

Rhopilema esculenta is a common jellyfish with high economic value in the coastal areas in China. The ephyra is an important stage of its growth and development. Under laboratory conditions, the feeding frequency (1, 2 and 3 times/d) of different specifications [D≤5; 5<D<9; D≥9 (D is the bell diameter)], light time (0 h, 8 h, 12 h, 16 h and 24 h/d) and light intensity [natural light (1 405 lx) and weak light (605 lx)] were used to study the effects of four factors on the growth of the ephyra. The results showed that the growth requirements of the ephyra with bell diameter of about 7 mm could be satisfied by feeding them twice a day under the conditions of temperature 21 ℃, salinity 20, pH 7.5 and dissolved oxygen 8.5-9.0 mg/L. The smaller the bell diameter, the higher the growth rate and the faster the growth rate. There were significant differences in the growth rate of ephyra at 0 h, 8 h, 24 h/d and 12 h, 16 h/d (P<0.05). There was no significant difference between 0 h, 8 h and 24 h/d (P>0.05). There was no significant difference between 12 h and 16 h (P>0.05), and 12 h/d light was the most favorable for the growth of ephyra.There was no significant difference between natural light and weak light on the growth of ephyra(P>0.05). The conclusion provides a scientific basis for the physiological study of growth stage and breeding technology of ephyra.