Abstract: Juvenile echiuran worm Urechis unicinctus with initial body weight of some 0.5 g were fed green alga Nannochloropsisi sp. (group Ⅰ), 3/2 Nannochloropsisi sp. + 1/3 Spirulina sp. powder (group Ⅱ) and 1/2 Nannochloropsisi sp. + 1/2 Phaeodactyum tricornutum (group Ⅲ) for 2 months to evaluate the effects of different diets on growth of juvenile echiuran worm. Clearance rate (CR) and filtration rate (FR) were further investigated in juvenile echiuran worm reared in a 6 L bucket with 10 cm sand bottom at water temperature of 15, 20, 25, and 30 ℃ and a salinity of 20, 24, 28 and 32 to study the effects of temperature and salinity on CR and FR of juvenile echiuran worm. The results showed that there was higher growth rate in the juveniles fed mixed diets and positive relationship between the CR/FR and salinity within a certain range. The CR and FR of the juveniles were increased with the increase in salinity at a salinitiy from 20 to 28, the maximum CR(262.16±3.90)mL/(ind.·h) and FR(123.41±0.74)×104 cells/(ind.·h) at a salinity of 28. The CR and FR of the juveniles were found to be increased with the rising water temperature from 15 ℃ to 25 ℃, the maximum CR of FR(251.33±10.16)mL/(ind.·h) at 20 ℃, and the peak FR of (159.11±4.35)×104 cells/(ind·h) at 25 ℃. The findings revealed that the weight gain rate of juveniles was related to food sources, with the best growth of echiuran worm fed mixed algae. The water temperature and salinity had distinct effect on CR and FR of the juvenile echiuran worm, with the optimum salinity of about 28 and the optimum water temperature of 20-25 ℃ for feeding of echiuran worm.
2018, Vol. 33 
