饵料种类、配比及投喂方式对单环刺螠幼虫生长和变态的影响

Effects of food species,proportion and feeding methods on growth and metamorphosis of larval echiuran worm Urechis unicinctus

为确定单环刺螠Urechis unicinctus人工苗种繁育中适宜幼虫生长发育的最佳饵料种类、配比及投喂方式,通过测定幼虫生长速率、成活率和变态率,对饵料品种、配比及投喂方式等进行了一系列对比试验研究。结果表明:饵料对单环刺螠幼虫生长和变态具有显著影响(P<0.05);单一饵料品种投喂结果显示,小球藻饵料组与球等鞭金藻饵料组的体节幼虫体长日增长率和幼虫成活率显著高于其他饵料组(P<0.05),但这两组间无显著性差异(P>0.05),小球藻饵料组的幼虫变态率(17.24%±0.89%)显著高于球等鞭金藻饵料组和其他饵料组(P<0.05),这表明小球藻是单一饵料投喂单环刺螠较好的开口饵料;混合饵料投喂结果显示,小球藻+球等鞭金藻+酵母粉混合饵料和小球藻+球等鞭金藻混合饵料组中,体节幼虫的体长日增长率和幼虫成活率显著高于其他混合饵料组(P<0.05),但这两个混合饵料组间无显著性差异(P>0.05),搭配投喂小球藻+球等边金藻+酵母粉混合饵料组的幼虫变态率(21.72%±0.85%)显著高于小球藻+球等鞭金藻混合饵料组和其他混合饵料组(P<0.05),这表明小球藻+球等边金藻+酵母粉的混合饵料组幼虫整体培育效果最佳;进一步的饵料配比及投喂方式研究显示,将小球藻、球等鞭金藻、酵母粉3种饵料按照2∶1∶1比例混合,在担轮幼虫前期只投喂小球藻+球等鞭金藻,至担轮幼虫中后期增加投喂酵母粉试验组,获得的幼虫变态率最高(24.73%±0.78%),显著高于其他试验组(P<0.05),且幼虫发育齐整度良好;饵料日投喂量结果显示,初孵担轮幼虫适宜的日投喂量为2×10^(4) cells/mL,随着幼虫发育饵料投喂量逐渐增加,当出现蠕虫状幼虫时日投喂量应增加至10×10^(4)~12×10^(4) cells/mL。研究表明,单环刺螠幼虫培育的最佳饵料投喂方案为,将小球藻、球等鞭金藻、酵母粉3种饵料按照2∶1∶1比例混合,在担轮幼虫前期只投喂小球藻+球等鞭金藻,至担轮幼虫中后期增加投喂酵母粉。

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.