Abstract: In order to find out the best food types and feeding methods suitable for the growth and development of the larvae in the artificial breeding of echiuran worm Urechisunicinctus, a feeding trial was conducted to probe into the optimal food types, proportions and feeding regimes by growth performance, survival rate and metamorphosis rate of the larvae.Newly hatched trochopores collected by artificial insemination and incubation of fertilized eggs from anatomic broodstock were reared in a 50 cm×30 cm×40 cm glass tank with bottom area of 0.15 m2 and 2-3 cm fine sand in depth at water temperature of 15.8-20.6 ℃ and fed live food(microalgae and yeast),formulated diets including Isochrysisgalbana(group A), Chlorellavulgaris(group B), Nitzschiaclosteriumf.minutissima(group C), marine red yeast(group D), live dry yeast(group E)and their combination including A+B, B+C, D+E, A+B+C, A+B+D, and A+B+E, simultaneous feeding and feeding in stages, twice or 3 times a day at a feeding rate of remnant food of 1×104 cells/mL when the larvae had a full stomach.One-way analysis of variance revealed that larval body length growth and metamorphosis were significant influenced by feeding(P<0.05).There were significantly higher daily growth rates in body length and larval survival rates in the larvae fed single live food C.vulgaris and I.galbana than those in other groups(P<0.05), without significant difference between the two groups(P>0.05), with the significantly higher larval metamorphosis rate(17.24%±0.89%)in C.vulgaris feeding group than that in I.galbana feeding group and other test groups(P<0.05), indicating that C.vulgaris was a better weaning diet for echiuran worm with a single diet.The echiuran worm fed the mixture food of C.vulgaris, I.galbana, and dry yeast powder and the mixture of C.vulgaris and I.galbana had significantly higher daily growth rates in body length and survival rates than the animals in other groups did(P<0.05), without significant difference between the two groups(P>0.05).Significantly higher larval metamorphosis rate was found in the echiuran worm fed the mixture food of C.vulgaris, I.galbana, and dry yeast powder(21.72%±0.85%)than that in the echiuran worm fed the mixture food of C.vulgaris and I.galbanaand in other test groups(P<0.05).The maximal metamorphosis rate(24.73%±0.78%)and synchronized development were observed in the echiuran worm fed the mixture food of C.vulgaris, I.galbana, and dry yeast powder at a ratio of 2∶1∶1, and fed only C.vulgaris and I.galbana in early trochophore, and increasing dry yeast powder in the mid-and late trochophore, significantly higher than those in other groups(P<0.05).The daily optimal feeding amount was shown to be 2×104 cells/mL for newly hatched trochopores at the first rearing stage, then to be gradually increased to 10×104-12×104 cells/mL for worm-shaped larvae with the development of larvae.The best rearing results of echiuran worm larvae were observed under the conditions of combination feeding of I.galbana, C.vulgaris, and live dry yeast at a ratio of 2∶1∶1, only I.galbana, C.vulgaris for early trochopores, and I.galbana, C.vulgaris + yeast powder for late trochopores, which provides valuable reference data for the large-scale artificial breeding of echiuran worm.
2021, Vol. 36 
