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Effects of food species，proportion and feeding methods on growth and metamorphosis of larval echiuran worm Urechis unicinctus
HU Liping, JIANG Liming, ZHANG Jianbai, ZHAO Qiang, HUANG Hua, WANG Liyong
Journal of Dalian Ocean University
2021, 36 (4):
587-594.
DOI: 10.16535/j.cnki.dlhyxb.2020-215
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
Urechis
unicinctus
, 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 m
2
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
Isochrysis
galbana
(group A),
Chlorella
vulgaris
(group B),
Nitzschia
closterium
f.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 1×10
4
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.galbana
and 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 2×10
4
cells/mL for newly hatched trochopores at the first rearing stage, then to be gradually increased to 10×10
4
-12×10
4
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.
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