许氏平鲉仔、稚鱼的摄食特性及幼鱼胃排空率

为阐明人工育苗条件下许氏平鲉早期发育阶段的摄食特性及变化规律,采用实验生态学方法,对人工育苗条件下许氏平鲉仔、稚鱼摄食特性及不同生长阶段幼鱼的胃排空率进行了研究。结果显示,许氏平鲉仔、稚鱼已具有较强的摄食能力,前期仔鱼(2日龄)昼夜摄食高峰出现于16:00;后期仔鱼(15日龄)与稚鱼(25日龄)的摄食高峰均出现在16:00—20:00,表现为白天摄食类型。许氏平鲉仔、稚鱼各阶段的日摄食率分别为42.26%(2日龄)、16.25%(15日龄)和13.07%(25日龄),可将其作为许氏平鲉早期发育阶段日投喂量的参考标准。在水温(22±0.5)°C条件下,摄食人工配合饵料的不同规格许氏平鲉幼鱼(平均体质量1.78和8.52 g)表现出明显不同的胃排空特征。采用线性模型、指数模型、平方根模型和Logistic模型均能较好地拟合实验幼鱼的胃排空数据。以R2、RSS、SDR为标准进一步比较,结果显示,体质量1.78和8.52 g幼鱼胃排空最佳拟合模型分别为线性模型和Logistic模型,其胃排空率分别为0.007和0.047 g/h,根据其胃排空特征以及投喂频率对幼鱼生长离散的影响等,建议将饱食投喂2~3次/d作为60~90日龄幼鱼的适宜投喂频率。     

牙鲆(Paralichthys olivaceus)仔稚幼鱼肠道菌群结构比较分析

采用MiSeq 16S rRNA高通量测序技术和生物信息学分析方法,构建了牙鲆(Paralichthys olivaceus)工厂化人工育苗模式下仔稚幼鱼阶段6个不同发育时期18个样品的16SrRNA基因测序文库,共获得7462个OTU (Operational Taxonomic Unit),分类为42个菌门972个菌属.对肠道菌群的形成过程及结构多样性变化分析显示,牙鲆初孵仔鱼的菌群组成多样性丰富,体内的优势菌为变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)和拟杆菌门(Bacteroidetes);在9日龄和21日龄摄食轮虫(Rotifer)和卤虫(Artemia sp.)幼体样品中,肠道的优势菌群结构较单一,变形菌门成为此时期肠道的优势菌群;45日龄摄食配合饲料后,肠道中变形菌门的相对丰度显著降低,厚壁菌门和拟杆菌门的相对丰度明显增大,成为肠道菌群的优势菌群.在属水平的菌群结构中发现,牙鲆仔稚幼鱼肠道优势菌群的种类和数量都发生了较大变化,在9日龄和21日龄时期肠道中弧菌属(Vibrio)相对丰度最高,到45日龄后相对丰度锐减到最低水平;拟杆菌属(Bacteroides)和普氏菌属(Prevotella)在80日龄后达到较高水平,成为肠道优势菌属;厚壁菌门的8个菌属在80-115日龄时期均发展成为优势菌属,定植于牙鲆的肠道.本研究揭示了工厂化人工育苗模式下牙鲆仔稚幼鱼肠道菌群结构及演替规律.     

牙鲆(Paralichthys olivaceus)仔稚幼鱼肠道菌群结构比较分析

采用MiSeq 16S rRNA高通量测序技术和生物信息学分析方法,构建了牙鲆(Paralichthys olivaceus)工厂化人工育苗模式下仔稚幼鱼阶段6个不同发育时期18个样品的16S rRNA基因测序文库,共获得7462个OTU(Operational Taxonomic Unit),分类为42个菌门972个菌属。对肠道菌群的形成过程及结构多样性变化分析显示,牙鲆初孵仔鱼的菌群组成多样性丰富,体内的优势菌为变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)和拟杆菌门(Bacteroidetes);在9日龄和21日龄摄食轮虫(Rotifer)和卤虫(Artemia sp.)幼体样品中,肠道的优势菌群结构较单一,变形菌门成为此时期肠道的优势菌群;45日龄摄食配合饲料后,肠道中变形菌门的相对丰度显著降低,厚壁菌门和拟杆菌门的相对丰度明显增大,成为肠道菌群的优势菌群。在属水平的菌群结构中发现,牙鲆仔稚幼鱼肠道优势菌群的种类和数量都发生了较大变化,在9日龄和21日龄时期肠道中弧菌属(Vibrio)相对丰度最高,到45日龄后相对丰度锐减到最低水平;拟杆菌属(Bacteroides)和普氏菌属(Prevotella)在80日龄后达到较高水平,成为肠道优势菌属;厚壁菌门的8个菌属在80–115日龄时期均发展成为优势菌属,定植于牙鲆的肠道。本研究揭示了工厂化人工育苗模式下牙鲆仔稚幼鱼肠道菌群结构及演替规律。     

鬼鲉早期发育阶段的摄食节律与饥饿致死时间

采用实验生态学方法研究鬼鲉(Inimicus japonicus)早期发育阶段的摄食特性和仔鱼饥饿致死时间.结果表明,仔鱼和营游泳生活的稚鱼摄食高峰出现在白天,并以白天摄食为主,6日龄仔鱼、17日龄营游泳生活稚鱼的摄食率高峰为10:00和14:00.随着生活习性的转变,其摄食节律也发生明显变化,稚鱼和幼鱼在营底栖生活方式的阶段,以夜间摄食为主,另一摄食小高峰出现在早晨.进入底栖生活阶段的29日龄稚鱼、40日龄幼鱼的摄食高峰为22:00和6:00.鬼鲉仔、稚、幼鱼各阶段的日摄食率分别为:6日龄仔鱼69.7%,17日龄稚鱼57.7%,29日龄稚鱼42.3%,40日龄幼鱼17.7%.在饥饿条件下鬼鲉初孵仔鱼、1、3、5、8和10日龄仔鱼的全部死亡时间分别为192 h、216 h、168 h、80 h、178 h和264 h,半数死亡时间分别为144h、120 h、120h、60h、108 h和144h,说明5日龄仔鱼是鬼鲉早期发育中最为敏感的阶段.饥饿仔鱼呈现头大、体短、身瘦、体色发白等形态特征,行为上表现为游动缓慢,反应迟钝和静卧底部.长期饥饿后仔鱼脑后部下陷明显,其形态特征可作为判断仔鱼饥饿致死的重要指标.     

2种活菌饲料对金鲫幼鱼肠道及水体微生态的影响

研究了2种活菌饲料对金鲫幼鱼肠道及水体菌群结构的影响,并分析了饲料、水体及肠道菌群进化关系。选取270尾规格整齐、体质健壮,平均体质量(8.49±0.26)g的金鲫幼鱼,利用嗜酸乳杆菌和枯草芽孢杆菌制备2种活菌饲料,以基础饲料为对照组A,基础饲料添加复合菌液为试验组B,复合菌液发酵基础饲料为试验组C,于室内循环水养殖系统中进行饲养试验。8周的饲养表明,与A组相比,摄食B组饲料的鱼,质量增加率显著提高5.15%(P0.05);摄食C组饲料的鱼,质量增加率显著降低3.44%(P0.05);养殖末期试验组水体中多核杆菌属、微小杆菌属等相对丰度明显增加(P0.05),黄杆菌属等相对丰度明显降低(P0.05),B组水体菌群物种丰度降低,多样性无明显变化,C组水体菌群物种丰度和多样性均明显降低;养殖末期B组试验鱼肠道菌群中气单胞菌属相对丰度明显降低(P0.05),微小杆菌属、柠檬酸杆菌属等相对丰度显著增加(P0.05),菌群多样性变高,物种丰度无明显变化;C组试验鱼肠道菌群中不动杆菌属、假单胞菌属等几乎消失,气单胞菌属、微小杆菌属、柠檬酸杆菌属等占绝对优势地位,菌群结构趋于简化。     

延迟投喂对许氏平鲉消化酶发育的影响

为查明许氏平鲉(Sebastes schlegelii)仔、稚鱼消化酶活性随日龄的变化过程,探讨消化酶的发育特性与饥饿的影响,以其初产仔鱼为研究对象,设置6个实验组,分别在1、2、3、4、5 d时开始初次投喂(即C、D1、D2、D3和D4组)和完全不投喂(S组)。结果显示,仔鱼前期的许氏平鲉消化酶的比活力波动较大,进入仔鱼后期(22 d后),消化酶比活力逐渐稳定;而总活力在仔、稚鱼阶段均不高,变化不显著,进入稚鱼后期后(26 d后)随日龄显著升高;存活的各实验组仔、稚鱼消化酶活力在相同日龄时差异并不显著,但由于前期的饥饿,实验结束时D2、D3组仔稚鱼的全长、体重和特定生长率均显著低于C、D1组。结果表明,延迟投喂时间对许氏平鲉的生长发育有显著影响,而且这种影响在生长后期很难恢复。     

玉米蛋白粉对大黄鱼生长、肠道组织结构及肠道菌群的影响

为了探讨玉米蛋白粉替代鱼粉对大黄鱼(Larimichthys crocea)生长、肠道组织结构及肠道微生物菌群的影响,进行了为期8周的生长实验。以初始体重为(10.49±0.03)g的大黄鱼幼鱼为研究对象,用玉米蛋白粉分别替代基础饲料(含40%鱼粉)中0%(FM,对照组)、15%(CGM15)、30%(CGM30)、45%(CGM45)、60%(CGM60)、75%(CGM75)的鱼粉,配制6种等氮(粗蛋白含量45%)等脂(粗脂肪含量10%)的实验饲料。56 d投喂实验结束后,各处理组幼鱼的存活率与特定生长率以及饲料系数等指标均无显差异(P0.05)。从肠道组织学发现,各处理组与对照组(FM)的幼鱼肠道组织结构肠黏膜、皱襞高度、杯状细胞个数均无显著差异性(P0.05),但CGM60组的幼鱼部分肠黏膜上皮细胞被破坏,上皮细胞排列紊乱,纹状缘出现缺刻,肠绒毛部分出现脱落或破损;CGM75组的幼鱼肠道的皱襞高度变短,皱襞密度降低,皱襞个数减少。选取FM、CGM15(生长相对较好)和CGM75(生长相对较差)三组运用Illumina-Mi Seq高通量测序技术分析幼鱼肠道菌群的物种丰富度指数(chao1)、香农指数(Shannon)、辛普森指数(Simpson)和覆盖率(good coverage)均无显著差异(P0.05);基于门水平,FM、CGM15和CGM75组的幼鱼肠道细菌中优势菌群为厚壁菌门(Firmicutes)和变形菌门(Proteobacteria)。而在属水平,类芽孢杆菌属(Paenibacillus)、嗜碱菌属(Alkaliphilus)、芽孢杆菌属(Bacillus)、肠球菌属(Enterococcus)为其优势菌群。分析属水平差异菌属发现,与FM组相比较,CGM15和CGM75组均显著增加了链球菌属(Streptococcus)的物种丰度(P0.05);与FM组相比,CGM15组显著降低了德沃斯氏菌(Devosia)和纤维弧菌属(Cellvibrio)的物种丰度(P0.05);与FM组相比,CGM75组显著增加了葡萄球菌属(Staphylococcus)的物种丰度(P0.05)。综上所述,玉米蛋白粉替代鱼粉达45%时对大黄鱼幼鱼的生长、肠道组织结构及肠道优势菌群均影响不大。     

野生和养殖丁肠道微生物菌群的比较分析

鱼类肠道菌群的结构和功能对其生长发育起重要作用。丁■是我国新疆地区特有的经济养殖鱼类，为评估野生丁■和养殖丁■肠道微生物菌群的结构和差异，以野生丁■和养殖丁■作为研究对象，采用Illumina Miseq高通量测序方法对其肠道16S rRNA基因的V3～V4区进行测序，比较两种环境条件下丁■肠道微生物菌群结构的丰度变化和差异。试验结果显示，丁■肠道微生物的优势菌群主要为变形菌门、厚壁菌门、放线菌门和拟杆菌门。但在两种环境下，其肠道菌群结构存在明显差异：在门水平下，梭菌门和酸菌门在养殖丁■中的丰度显著低于野生丁■(P<0.05);在属水平下，乳酸杆菌属和不动杆菌属在养殖丁■中的丰度高于野生丁■,而支原体和黄杆菌属则显著低于野生丁■(P<0.01);在种水平下，洛菲不动杆菌在养殖丁■中的含量显著高于野生丁■(P<0.01),而未分类的黄杆菌则显著低于野生丁■(P<0.05)。试验结果表明，由于饲养环境的改变，野生丁■和养殖丁■肠道菌群的组成及丰度出现显著变化。该结果可为后续丁■肠道微生物的研究和养殖管理提供基础数据和参考。     

人工鱼礁和大型海藻对许氏平鲉和大泷六线鱼幼鱼的诱集作用

为了探究大型海藻和人工鱼礁对鱼类的诱集作用,依据崂山湾人工鱼礁区游泳动物和大型海藻调查结果,以海黍子、孔石莼、带形蜈蚣藻、石花菜和小珊瑚藻5种优势藻类,许氏平鲉和大泷六线鱼2种优势鱼类以及人工鱼礁模型为研究对象,于室内实验水槽观察了许氏平鲉和大泷六线鱼幼鱼在海藻和模型礁中的行为反应和分布。结果显示,水槽中未投放模型礁和海藻时,实验鱼密集出现在水槽边缘区(A9),分布率分别为75.71%±7.79%和73.63%±4.41%。放入模型礁和海藻丛后,许氏平鲉和大泷六线鱼出现短暂的排斥反应,然后迅速聚集其中;2种鱼对带形蜈蚣藻的响应时间最短[(12.75~21.00)s],对模型礁的响应时间最长[(66.50~151.25)s];带形蜈蚣藻聚集许氏平鲉用时最短[(151.50±8.14)s],海黍子聚集大泷六线鱼用时最短[(56.00±2.53)s];大泷六线鱼对模型礁的聚集时间为(216.25±5.59)s,远低于许氏平鲉(1343.50±5.38)s;2种鱼在模型礁中的停留时间远长于海藻丛,且大泷六线鱼的停留时间(211.85±7.96)s长于许氏平鲉(199.75±16.82)s。海藻丛和模型礁对2种岩礁性幼鱼的诱集效果明显,实验区幼鱼的分布率由未投放模型礁和海藻前的0.91%~8.78%上升到4.21%~31.42%;高密度带形蜈蚣藻和海黍子的诱集效果最好,对许氏平鲉和大泷六线鱼的聚集率分别达到30.42%±1.14%和31.42%±1.74%,而低密度小珊瑚藻的诱集作用不明显。     

线纹尖塘鳢池塘规模化育苗技术研究

线纹尖塘鳢仔鱼期历时14~15 d,初孵仔鱼个体只有2.85 mm;混合营养期短,仅2~3 d,这对仔鱼的成活极为不利。仔幼鱼的摄饵大小L(mm)与口宽D(mm)呈正相关,关系式为D=2.0349L 0.2371,开口饵料大小为150~200μm轮虫。15日龄进入稚鱼期,历时29~30 d;27日龄后,全长约15 mm的稚鱼可以驯食人工混合饲料。45日龄后仔鱼发育成早期幼鱼,此时全长约27.2 mm。依仔幼鱼的食性与生长发育特性,2002~2005年间进行池塘规模化育苗,由前期仔鱼育成全长22.0~34.0 mm早期幼鱼523.7万尾,成活率20.3%~21.7%。     

池塘养殖牙鲆肠道和环境菌群结构对益生菌制剂的响应

为研究益生菌制剂对池塘养殖牙鲆(Paralichthys olivaceus)肠道及环境菌群结构的调控效果,采用高通量测序技术和生物信息学分析手段构建牙鲆肠道、养殖水体、饵料和池塘底泥的16S rDNA基因测序文库,分析不同样品中菌群组成和多样性在益生菌制剂调控过程中的变化趋势.结果显示,添加益生菌制剂后,池塘底泥和牙...     

Structural characteristics and succession of intestinal microbiota for Paralichthys olivaceus during the early life stage

The research of intestinal microflora structures for Paralichthys olivaceus larvae and juveniles will help us to master the ontogeny and developmental colonization of microflora during the larval rearing stage. In this study, we sequenced the total bacterial genomic DNA in larval and juvenile guts with an Illumina MiSeq PE300 system, and analysed the structural characteristics of these microbiota, feed and rearing water in live and formulated feeding periods. The structure of gut microbiota was gradually similar to those in wild P. olivaceus at the phylum level and the newly hatched ones with the growth, according to the distribution and abundance of intestinal microbiota. And the colonized rule of main microbial species in guts was decreased initially and then increased during the larvae and juveniles stage. Meantime, the core microflora of this study were obtained through the analysis of shared and dominant species, which included Bacteroides, Bacillus, Enterococcus, Lactobacillus, Lactococcus, Escherichia_Shigella, Acinetobacter, Pseudomonas, Vibrio, Nitrosomonas, and Glaciecola. The correlation analysis of microbiota between intestines and environmental factors suggested that microflora in feed and water could affect the distribution of larval and juvenile gut microbiota. Moreover, many species of Acinetobacter, Pseudomonas and Vibrio are treated as important potential pathogens in aquaculture. These all pointed out the microbial quality of feed and rearing water should be strictly controlled in fish breeding and farming, and supply theoretical bases for screening the native probiotics to artificially regulate the gut microbiota.     

高通量测序分析凡纳滨对虾育苗期水体菌群结构特征

为了解凡纳滨对虾育苗期正常苗池水体菌群结构和多样性变化,实验采用Illumina MiSeq高通量测序水体细菌16S rDNA V4区,比较幼体在无节V期(N5)、溞状Ⅱ期(Z2)、糠虾Ⅰ期(M1)与仔虾Ⅰ期(P1)时的水体菌群特征。结果显示,水体菌群Shannon多样性指数随幼体发育先降后升,而Pielou均匀度指数除在N5时稍高外,在其余阶段都很接近。育苗期间,变形菌门为水体绝对优势菌群(50.0%~88.0%),尤其红杆菌科从N5到P1阶段分别占24.2%、61.6%、43.3%和51.8%;拟杆菌门在各期丰度均9.7%,其中腐螺旋菌科以5.3%~16.9%优势分布于后3个阶段;放线菌门在后3个期都为优势类群,并以微杆菌科为主,丰度分别达5.6%、37.6%和10.8%;而疣微菌门只在P1时表现为优势(5.3%)。苗池水体核心菌属主要由洛克氏菌、海命菌、栖东海菌、亚硫酸杆菌和2个分类未定属构成。可见水体菌群呈高度多样而动态变化,且N5菌群明显区别于后3个阶段。育苗期间水体主要环境因子总体波动较小,对优势操作分类单元(OTU)丰度分布无显著影响。研究表明,凡纳滨对虾健康苗池水体菌群随幼体发育和饵料投喂而明显更替,其中核心菌群的潜在功能对维持水体生态系统稳定起重要作用,可为对虾育苗益生菌与健康苗池指示菌的筛选提供依据。     

营养代谢过程中黄条鰤幼鱼消化道菌群的演变趋势

为认识消化道菌群结构在宿主营养代谢过程中的变化规律,并探讨饵料菌群对其的影响,采用16SrDNA高通量测序技术,对黄条鰤(Seriola lalandi)幼鱼一个完整摄食周期内的消化道菌群结构特征进行研究,并解析其与饵料菌群的相关性.结果显示,乳杆菌属(Lactobacillus)、假单胞菌属(Pseudomonas)...     

Phylogenetic analysis of intestinal bacteria of freshwater salmon Salmo salar and sea trout Salmo trutta trutta and diet

The microbial diversity of culturable intestinal microflora of wild freshwater salmonid fishes salmon Salmo salar and sea trout Salmo trutta trutta juveniles (0+ years old) from the same environmental conditions were investigated by means of molecular identification techniques and analysis of diet. Significant differences in the intestinal microbial diversity were observed in different fish species. The predominant group in the intestinal tract of the salmon comprised representatives of the Enterobacteriaceae family (23%), Plesiomonas (19.2%) and Carnobacterium (15.3%). Predominant microbiota in sea trout intestinal tract were Enterobacteriaceae (52%), Aeromonas (22%) and Pseudomonas (14%). The results show that Enterobacteriaceae were predominant in the intestinal tract of the salmon and the sea trout juveniles raised on diets of different compositions. However, molecular identification of the intestinal microbiota at the species or genus level revealed differences in these fish species. Bacteria in the hindgut of salmon included Pragia and Serratia. However, bacteria in the gut contents of sea trout from the Enterobacteriaceae family were Buttiauxella, Enterobacter, Moellerella, Pantoea, Rahnella and Tiedjeia arctica. A novel phylotype of T. arctica is harbored in the intestinal tract of wild salmon, and may correspond to a previously undescribed species.     

投喂鲍内脏多糖对罗非鱼肠道菌群结构的影响

利用PCR-DGGE和Illumina测序技术研究了罗非鱼(Oreochromisniloticus)肠道菌群结构及饲喂鲍内脏多糖后罗非鱼肠道菌群的动态变化。在罗非鱼肠道中检测到13个门的细菌,其中梭杆菌门(Fusobacteria,77.84%)为优势菌门,拟杆菌门(Bacteroidetes, 8.59%)、衣原体门(Chlamydiae, 6.18%)、变形菌门(Proteobacteria, 5.84%)和放线菌门(Actinobacteria, 1.20%)为次优势菌门,还检测到Saccharibacteria等8个菌门和一些未知类群。在属的水平上,优势菌属为鲸杆菌属(Cetobacterium)、Neochlamydia、邻单胞菌属(Plesiomonas)和不动杆菌属(Acinetobacter),分别占77.84%、5.796%、2.64%和1.13%,还有一个紫单胞菌科(Porphyromonadaceae)的未知属,占8.29%。此外还有分枝杆菌属(Mycobacterium)等6个菌属和一些未知属。投喂添加鲍多糖的饲料对罗非鱼肠道微生物的构成造成了明显影响,饲喂鲍多糖的处理组和饲喂普通饲料的对照组样品分别聚为两大类。投喂添加鲍多糖饲料后,放线菌门、Saccharibacteria、疣微菌门和TM6_Dependentiae的丰度显著下调;在属的水平上,邻单胞菌属、鲸杆菌属的丰度上调;Neochlamydia、不动杆菌属、分枝杆菌属、Alsobacter、Aquicella、假单胞菌属、气单胞菌属、Alpinimonas等属的丰度下调。其中分枝杆菌属、Alsobacter、Aquicella和邻单胞菌属的丰度与对照差异显著(P0.05)。在种水平上,一些潜在致病菌,如鲍曼不动杆菌(Acinetobabacterbaumannii)、龟分枝杆菌(Mycobacteriumabscessus)、Aeromonas sharmana、耐酪酸冢村菌(Tsukamurella tyrosinosolvens)、铜绿色假单胞菌(Pseudomonas aeruginosa)等的丰度下调,其中龟分枝杆菌和耐酪酸冢村菌与对照差异显著(P0.05),而鲸杆菌属等有益菌的丰度上调。本研究从肠道微生物的角度来研究鲍内脏多糖对宿主的影响,为海洋生物活性物质的功效评价提供了新思路,也为鲍内脏活性物质的开发利用、益生元的研制等奠定理论基础。     

Daily ration of Japanese Spanish mackerel Scomberomorus niphonius larvae

SUMMARY: Diel successive samplings of Japanese Spanish mackerel Scomberomorus niphonius larvae were conducted throughout 24 h both in the sea and in captivity in order to estimate their daily ration. Using the Elliott and Persson model, the instantaneous gastric evacuation rate was estimated from the depletion of stomach contents (% dry bodyweight) with time during the night for wild fish (3.0–11.5 mm standard length) and from starvation experiments for reared fish (8, 10, and 15 days after hatching (DAH)). Japanese Spanish mackerel is a daylight feeder and exhibited piscivorous habits from first feeding both in the sea and in captivity. Feeding activity peaked at dusk. The estimated daily ration for wild larvae were 111.1 and 127.2% in 1996 and 1997, respectively; and those for reared larvae ranged from 90.6 to 111.7% of dry bodyweight. Based on the estimated value of daily rations for reared fish, the total number of newly hatched red sea bream Pagrus major larvae preyed by a Japanese Spanish mackerel from first feeding (5 DAH) to beginning of juvenile stage (20 DAH) in captivity was calculated to be 1139–1404.     

Faster growth before metamorphosis leads to a higher risk of pseudoalbinism in juveniles of the starry flounder <Emphasis Type="Italic">Platichthys stellatus</Emphasis>, as suggested by otolith back-calculation

The mechanism underlying malformation during flatfish metamorphosis is not clear. Here, the relationship between growth before metamorphosis and the occurrence of malformation after metamorphosis was examined in individuals reared in a single tank. Otoliths of starry flounder Platichthys stellatus larvae were labeled with alizarin complexone before metamorphosis [12 days after hatching (DAH)]. The positive linear regression between the lapillus otolith diameter and body length at 12 DAH enabled the estimation of individual larval size after completion of metamorphosis. At 12 DAH, the average body length of the typical pseudoalbino juveniles was significantly greater (5.37 mm) than that of the normal juveniles (5.13 mm) (P < 0.01, n = 100). In addition, of the larvae that were estimated to measure less than 4.8 mm at 12 DAH, approximately 80% metamorphosed into normal juveniles, whereas more than 60% of the larvae that measured more than 5.4 mm became pseudoalbino juveniles. These results indicate that the larvae that grow rapidly during the first 12 days are more likely to become pseudoalbino individuals after metamorphosis.     

饲料中添加大豆皂甙对大菱鲆幼鱼生长和肠道健康的影响

为研究大豆皂甙对大菱鲆幼鱼生长性能、消化酶活性、肠道组织结构完整性和肠道菌群结构的影响,在以鱼粉为蛋白源的基础饲料中分别添加0%和0.3%的大豆皂甙,配制成鱼粉组和大豆皂甙组2种等氮等脂的实验饲料来投喂体质量为(4.63±0.01) g的大菱鲆进行12周的摄食生长实验。结果显示,饲料中添加0.3%的大豆皂甙对大菱鲆的生长性能没有产生显著影响,但显著降低了胃蛋白酶及肠淀粉酶活性;2组实验中大菱鲆肠道组织形态无明显差异,但大豆皂甙组肠道紧密连接蛋白的基因表达量显著降低。肠道菌群分析结果显示,大菱鲆肠道中相对丰度最高的门和属分别为变形菌门和盐单胞菌属。LEfSe和MetaStat分析显示,饲料中添加大豆皂甙后显著提高了大菱鲆肠道内优势菌(变形菌门及希瓦氏菌属),皂甙水解相关的肠道微生物(鞘脂单胞菌属、普氏菌属、栖瘤胃普雷沃菌以及普通拟杆菌)及潜在致病菌(莫氏杆菌属和发光杆菌属)的相对丰度,同时显著降低了Caenimonas、Niastella和条件致病菌罗尔斯通菌属的相对丰度。研究表明,0.3%大豆皂甙抑制了大菱鲆消化酶活性及肠道紧密连接蛋白的基因表达,且引起了大菱鲆肠道菌群结构的显著改变。因此,大豆皂甙对鱼类肠道健康尤其是肠道菌群的影响不容忽视,值得进一步研究。