Comparative genomic insights into the taxonomy of Edwardsiella tarda isolated from different hosts: Marine,freshwater and migratory fish

Edwardsiella tarda, a Gram‐negative member of the family Enterobacteriaceae, has been isolated from many animal species worldwide, especially fish species. Its broad host range indicates the diversity in taxonomy, which attracted the attention of many researchers. Here, we added genome of E. tarda strain isolated from freshwater fish to comparative genomics study for the first time. We sequenced and assembled the genome of E. tarda ASE201307 which was isolated from freshwater Asian swamp eel. ASE201307 genome contained a single circular chromosome of 3.68M with G+C 57.09% content. Comparative genomics including SNP calling, synteny block, Core/Pan genes analysis and phylogeny analysis was conducted among ASE201307 and other Edwardsiella strains isolated from different fish species. Results of SNP analysis and synteny block demonstrated the close relative of ASE201307, FL95.01 and DT which were all isolated from freshwater fish. In further analysis heat map of dispensable genes and phylogenetic tree, all E. tarda strains were divided into two groups. One was isolated from freshwater fish and the other was isolated from marine/migratory fish. Based on all studies above, we proposed the living environment of hosts as a new taxonomic character and divided E. tarda isolated from diseased fish into freshwater group and marine/migratory group.     

额尔齐斯河三代虫种类研究及新纪录种记述

为探究额尔齐斯河水域中鱼类寄生三代虫的种类以及感染情况,给新疆水产业的发展及我国三代虫的研究提供基础资料,2009年8月至2014年8月选取额尔齐斯河的北屯镇、185团场、布尔津和哈巴河4个采样点,自捕或者从当地渔民处购买材料鱼,通过染色观察三代虫的形态特征,对其几丁质结构进行绘图、测量及比较,同时对不同种类三代虫的感染率、感染强度、感染丰度以及宿主专一性进行分析。结果表明,4个采样点共发现三代虫14种,其中丁 三代虫（Gyrodactylus tinca Malmberg,1957）、白斑狗鱼三代虫（Gyrodoctylus lucii Kulakowskaja,1951）、梭鲈三代虫（Gyrodoctylu luciopercae Gusev,1962）、马氏三代虫（Gyrodactylus markakulensis Gvosdev,1950）均是国内首次发现,为新纪录种;感染率最高的为鲤（Cyprinus carpio）（23．94％）,最低的为河鲈（Perca fluviatilis）（0．74％）,除东方欧鳊（Abramis brama orientalis）、散鳞镜鲤（Cyprinus carpio haematopterrus）和鲤外,其余的感染率均不超过10％;银鲫（Carassius auratus gibelio）、散鳞镜鲤和鲤为易感宿主,方均比（S2／X）都大于1,呈聚集分布;其余的小于1,呈均匀分布。三代虫宿主专一性较强,但有少数种类三代虫寄生2～4种宿主的情况,也存在同一宿主感染2～3种三代虫的现象,与单殖吸虫的宿主专一性基本一致。     

Methods for identification and differentiation of different Shewanella spp. isolates for diagnostic use

Shewanella spp. are Gram‐negative, rod‐shaped, motile bacteria that are widely distributed in marine and freshwater environments. The bacteria are present in the physiological microflora of fish from temperate waters and are known as fish spoilage species. From clinically healthy fish and from fish with skin ulcerations, Shewanella spp. is regularly isolated, indicating a possible role as fish pathogen. In this study, 74 isolates of Shewanella spp. were analysed. For species identification, biochemical techniques, 16S rRNA sequencing, MALDI‐TOF MS and the Sherlock Microbial Identification System (MIS) based on the composition of fatty acid ethyl esters were compared. The phylogenetic relationship, cytotoxicity in vitro and resistance against antibiotics were tested. The most reliable method for species identification was 16S rRNA sequencing. From diseased fish, clinically healthy fish and the aquatic environment, different Shewanella species were isolated. This indicates that Shewanella spp. is widespread in the aquatic milieu and acts as a secondary pathogen. The virulence of Shewanella spp. is probably not depending on the species but on the isolate itself. Many isolates of Shewanella spp. were showing multiresistances against antibiotic substances, especially in samples derived from retailers and in routine diagnostics, all Shewanella spp. should therefore be tested for resistances against antibiotic agents.     

Viral haemorrhagic septicaemia virus in marine fish and its implications for fish farming--a review

Viral haemorrhagic septicaemia virus (VHSV) has, in recent decades, been isolated from an increasing number of free-living marine fish species. So far, it has been isolated from at least 48 fish species from the northern hemisphere, including North America, Asia and Europe, and fifteen different species including herring, sprat, cod, Norway pout and flatfish from northern European waters. The high number of VHSV isolations from the Baltic Sea, Kattegat, Skagerrak, the North Sea and waters around Scotland indicate that the virus is endemic in these waters. The VHSV isolates originating from wild marine fish show no to low pathogenicity to rainbow trout and Atlantic salmon, although several are pathogenic for turbot. Marine VHSV isolates are so far serologically indistinguishable from freshwater isolates. Genotyping based on VHSV G- and N-genes reveals four groups indicating the geographical origin of the isolates, with one group representing traditional European freshwater isolates and isolates of north European marine origin, a second group of marine isolates from the Baltic Sea, a third group of isolates from the North Sea, and a group representing North American isolates. Examples of possible transfer of virus from free-living marine fish to farmed fish are discussed, as are measures to prevent introduction of VHSV from the marine environment to aquaculture.     

Mycobacteria isolated from Chesapeake Bay fish

Mycobacteriosis in fish can result in ulcers, emaciation, and in some cases death. Mycobacteria have been previously isolated from a variety of Chesapeake Bay fish species, and the current study was designed to identify potential host specificity and location fidelity of mycobacterial isolates. Mycobacteria were isolated from wild fish of the Chesapeake Bay collected from the Upper Bay, the Choptank River, Herring Bay, the Chicamacomico River, the Pocomoke River and the Potomac River in 2003–2006. Mycobacterial isolates were recovered from striped bass, Morone saxatilis , Atlantic menhaden, Brevoortia tyrannus , white perch, Morone americana , summer flounder, Paralichthys dentatus , spot, Leiostomus xanthurus , largemouth bass, Micropterus salmoides , channel catfish, Ictalurus punctatus , common carp, Cyprinus carpio carpio , spotted seatrout, Cynoscion nebulosus , killifish, Fundulus sp., blueback herring, Alosa aestivalis , American gizzard shad, Dorosoma cepedianum and American silver perch, Bairdiella chrysoura . Twenty-nine well-defined mycobacterial groups resulted from gas chromatography dendrogram clustering of isolates. The majority of groups included more than one host species and more than one site of collection. However, four groups contained only striped bass isolates, three of which were similar to M. shottsii . Therefore, multiple Chesapeake Bay fish species are colonized with multiple mycobacterial isolates, of which few appear to be host or location specific.     

发病鲆鲽类分离菌株的16S rRNA基因测序分析

细菌性疾病是中国海水养殖鲆鲽类的主要病害,为全面了解病原菌种类,本研究对1999~2012年从山东、江苏、河北、天津等沿海地区养殖场发病鲆鲽鱼类中分离得到的124株优势菌株进行了16S rRNA基因测序和系统发育学分析。将基因序列与GenBank核酸序列数据库进行相似度比对分析,结果显示,有83株与弧菌属(Vibriosp.)细菌相似度最高,11株与气单胞菌属(Aeromonas sp.)细菌相似度最高,4株与爱德华氏菌属(Edwardsiella sp.)细菌相似度最高,26株为其他15种属的细菌。根据系统发育学分析结果,进一步将66株菌鉴定为16个种,优势种为溶藻弧菌(V.alginolyticus)、哈氏弧菌(V.harveyi)、鳗弧菌(V.anguillarum)、杀鲑气单胞菌(A.salmonicida)和迟缓爱德华氏菌(E.tarda)。选择其中的9株鳗弧菌和4株迟缓爱德华氏菌进行人工感染实验,结果显示,其中7株鳗弧菌和3株迟缓爱德华氏菌对大菱鲆(Scophthalmus maximus)有较强的致病性。研究结果可为阐明中国海水养殖鲆鲽类的流行病发生历史、病原种类、病原监测及疾病控制提供重要参考。     

Demonstrating the practical impact of studies on biotic interactions and adaptation of a threatened unionoid mussel (Margaritifera margaritifera) to its host fish (Salmo trutta)

1. To understand the ecological factors behind the decline of functionally important threatened species with complex life cycles, many different life‐cycle stages need to be investigated. The highly threatened unionoid freshwater mussels, with their complex life cycle, including a parasitic stage on host fish, often have a large influence on biodiversity and ecosystem functioning.
2. The overall aim of the present article is to summarize and discuss the impact of two articles published in Aquatic Conservation: Marine and Freshwater Ecosystems (AQC) on biotic interactions and adaptation of a threatened unionoid mussel (Margaritifera margaritifera) to its host fish (Salmo trutta).
3. The two AQC publications described research on the influence of population size and density of mussels and host fish, and host–parasite interactions between mussels and their host fish, on the recruitment of juvenile mussels.
4. The results from these publications filled gaps in knowledge and resulted in recommendations and incentives for conservation. The results and method development have been used in practical conservation work with threatened mussel species and have been implemented and cited in management handbooks. The outcome of the publications has been implemented in large conservation and restoration projects, and in several recent scientific publications.
5. Specifically, the results from one publication showed that ecological parameters such as mussel and host fish density and population size influenced recruitment of the threatened freshwater pearl mussel. The results from the second publication showed that understanding host–parasite interactions is important for comparing the suitability of host fish strains, and that host fish strains differ in their suitability for mussel infestations. In combination, the articles show that integrating ecological parameters of threatened mussels and their host fish with host–parasite interaction experiments can be an important influence on conservation recommendations, adaptive management and national management programmes for threatened species.

     

Effect of salinity on the biosynthesis of n-3 long-chain polyunsaturated fatty acids in silverside Chirostoma estor

The genus Chirostoma (silversides) belongs to the family Atherinopsidae, which contains around 150 species, most of which are marine. However, Mexican silverside (Chirostoma estor) is one of the few representatives of freshwater atherinopsids and is only found in some lakes of the Mexican Central Plateau. However, studies have shown that C. estor has improved survival, growth, and development when cultured in water conditions with increased salinity. In addition, C. estor displays an unusual fatty acid composition for a freshwater fish with high docosahexaenoic acid (DHA)/ eicosapentaenoic acid (EPA) ratios. Freshwater and marine fish species display very different essential fatty acid metabolism and requirements, and so the present study investigated long-chain polyunsaturated fatty acid (LC-PUFA) biosynthesis to determine the capacity of C. estor for endogenous production of EPA and DHA, and the effect that salinity has on these pathways. Briefly, C. estor were maintained at three salinities (0, 5, and 15 ppt), and the metabolism of 1?C-labeled 18:3n-3 was determined in isolated hepatocyte and enterocyte cells. The results showed that C. estor has the capacity for endogenous biosynthesis of LC-PUFA from 18-carbon fatty acid precursors, but that the pathway was essentially only active in saline conditions with virtually no activity in cells isolated from fish grown in freshwater. The activity of the LC-PUFA biosynthesis pathway was also higher in cells isolated from fish at 15 ppt compared with fish at 5 ppt. The activity was around fivefold higher in hepatocytes compared with enterocytes; although the majority of 18:3n-3 was converted to 18:4n-3 and 20:4n-3 in hepatocytes, the proportions of 18:3n-3 converted to EPA and DHA were higher in enterocytes. The data were consistent with the hypothesis that conversion of EPA to DHA could contribute, at least in part, to the generally high DHA/EPA ratios observed in the tissue lipids of C. estor.     

Protozoan parasites of gilthead sea bream, Sparus aurata L., from different culture systems in Spain

Abstract. In a parasitic survey of gilthead sea bream, Sparus aurata L., cultured in different systems in Spain, eight protozoan species were found. Ectoparasites included two ciliates ( Trichodina sp. and a Cryptocaryon -like species), one dinoflagellate ( Amyloodinium sp.) and the zooflagellate Ichthyobodo sp. Endoparasites were represented by members of the Apicomplexa ( Eimeria sp.) and Myxosporea ( Polysporoplasma sparis. Ceratomyxa sp. and Leptotheca sp.). Ichthyobodo sp., Eimeria sp., Ceratomyxa sp. and Leptotheca sp. are reported for the first time in S. aurata. Amyloodinium sp. and Ichthyobodo sp. were associated with outbreaks of disease in larval and juvenile fish. Data on prevalence and intensity of infection and the location in the host are provided. The potential importance of these protozoan parasites for gilthead sea bream culture is discussed.     

Particularities of early life stages in temperate freshwater fish species: comparisons with marine species and implications for aquaculture practices

Both egg and larvae are different between freshwater and marine fish species. Freshwater fish species have generally larger and fewer eggs than marine species. Most freshwater fish species have demersal eggs that develop stuck to various substrata, such as plants or gravels, while eggs of most marine fish species develop in the water column. These differences have consequences for both the evaluation of the quality and the incubation of eggs of freshwater fish species compared with marine species. The larvae of many freshwater fish species are larger and more developed at hatching than their marine counterparts: thus, larval feeding regimes could be different and cannibalism may emerge sooner in certain freshwater fish species. The main differences of egg and larvae between freshwater and marine species are highlighted and the possible implications for aquaculture practices are discussed.     

Genetics of neotropical fish: from chromosomes to populations

The Neotropical freshwater fish fauna is very rich—according to the most recent catalogue 71 families and 4,475 species have been described. However, only a small amount of general information is available on the composition of Neotropical marine fishes. In Brazil, 1,298 marine species have been recorded. General analysis of available cytogenetic and population genetic data clearly indicates research has been mainly concentrated on freshwater fishes. Thus, today, cytogenetic information is available for 475 species of Characiformes, 318 species of Siluriformes, 48 species of Gymnotiformes, 199 freshwater species that do not belong to the superorder Ostariophysi, and only 109 species of marine fishes. For the species studied, only about 6% have sex chromosomes and about 5% have supernumerary or B chromosomes. A review of the cytogenetic studies shows that these data have provided valuable information about the relationships between fish groups, the occurrence of cryptic species and species complexes, the mechanism of sex determination and sex chromosome evolution, the distribution of nucleolus organizer regions, the existence supernumerary chromosomes, and the relationship between polyploidy and evolution. In relation to populations in Neotropical marine waters, the studies have shown the presence of cryptic species, which has important implications for fishery management. Different levels of genetic structuring can be found among Neotropical freshwater migratory fish species. This raises important implications for fish population genetic diversity and consequently its sustainable utilization in inland fisheries and aquaculture, specifically for conservation of ichthyo-diversity and survival.     

Antiparasitic activity of the antimicrobial peptide HbβP‐1, a member of the β‐haemoglobin peptide family

A family of antimicrobial peptides (AMPs) derived from the β‐subunit of haemoglobin was recently isolated from channel catfish, Ictalurus punctatus, infected with Ichthyophthirius multifiliis (ich), an important freshwater fish parasite that causes ichthyophthiriosis. We previously discovered that one of these AMPs, HbβP‐1, had strong cidal activity against ich as well as another ectoparasite, Tetrahymena pyriformis. HbβP‐1 toxicity was specific, primarily affecting the trophozoite (trophont) stage of ich. Here, we show that HbβP‐1 acts more rapidly to kill smaller (presumably less mature) trophonts of ich, taking almost twice as long to kill larger trophonts (P < 0.0001). It acts more rapidly than an unrelated AMP, piscidin 1, which is haemolytic and also lethal to ich trophonts. HbβP‐1 is potently and selectively lethal to the trophont stage of the dinoflagellate ectoparasite, Amyloodinium ocellatum, one of the most important pathogens of warmwater marine fish. HbβP‐1 has no effect on the fish gill cell line feeder layer (G1B cells) used to propagate Amyloodinium, further suggesting a highly selective action. These findings suggest that HbβP‐1 or related AMPs might function in protecting marine as well as freshwater fish and that HbβP‐1 has highly selective activity against specific life stages of important fish ectoparasites.     

The role of management practices in fish kills in recreational lake fisheries in England and Wales

Abstract  In England and Wales, freshwater anglers have shifted their behaviour towards visiting catch-and-release lake fisheries that are intensively stocked, mainly of large common carp, Cyprinus carpio L., to maintain high catch rates. Of 187 fish kills investigated in these intensively stocked lake fisheries in 2004 and 2005, most occurred between April and June and were mainly caused by parasitic or bacterial infections. Bacteria were usually associated with ulcerative diseases caused by strains of the bacterium Aeromonas salmonicida (Emmerich & Weibel) and secondary infections of opportunistic bacteria of the Genus Aeromonas (excluding salmonicida ) and Pseudomonas . Parasites involved in fish kills included Ichthyophthirius multifiliis (Fouquet), Chilodenella sp., Ichthyobodo necator (Henneguy) and Argulus sp. Outbreaks were typically in fisheries with high extant stock densities (>1500 kg ha⁻¹) and sub-optimal habitats, for example of low habitat heterogeneity with few macrophytes in the littoral zone. Recent stocking was also a key factor when only carp was affected. Thus, certain fisheries management practices that aim to enhance fishery performance may instead trigger fish kills during spring.     

Neoparamoeba branchiphila n. sp., and related species of the genus Neoparamoeba Page, 1987: morphological and molecular characterization of selected strains

A total of 18 Neoparamoeba strains were characterized both morphologically and using the SSU rRNA gene sequences as molecular markers. Nine were isolated from gills of farmed Atlantic salmon, Salmo salar L., six from sediments sampled in areas of sea-cage farms and three from net material of sea-cages. The newly obtained sequences extended substantially the dataset of Neoparamoeba strains available for phylogenetic analyses, which were used to infer taxonomic relatedness among 32 strains morphologically assigned to this genus. In addition to the N. pemaquidensis and N. aestuarina clades, phylogenetic analyses clearly distinguished a third clade with sequences from six strains. Members of this clade are characterized as representatives of a new species, N. branchiphila n. sp. The diagnostic primers for the identification of this species are introduced.     

鲤trim25多拷贝基因进化和表达调控初探

天然免疫系统是硬骨鱼类抵抗病毒感染的主要防御系统,三重基序(tripartite motif, TRIM)蛋白家族作为天然免疫系统的重要组成部分,参与病毒感染的免疫网络调控,其中,TRIM25已被证实在多种鱼类的免疫反应中发挥重要作用。本研究对鲤(Cyprinus carpio) trim25基因的16个拷贝进行了序列进化分析、共线性分析和功能域结构分析,并比较了各拷贝在组织中的表达和顺式调控位点的差异。序列比对和系统进化分析结果均显示,位于鲤11和12号染色上、结构完整的TRIM25的2个拷贝与金线鲃(Sinocyclocheilus grahami)和斑马鱼(Danio rerio)的TRIM25蛋白结构高度相似,与鲤科鱼类以外的其他物种的结构差异较大。基因共线性结果显示,trim25基因上下游基因在不同物种的进化过程中相对保守。鲤TRIM25蛋白的结构分析显示,在鲤TRIM25的16个拷贝中,有6个拷贝具有完整功能结构域,其中,各有5个拷贝在鲤的肝与脑组织中高表达。在构建的表达数量性状基因座(eQTL)调控网络中,在肝和脑组织中分别筛选到5个和17个顺式调控trim25基因表达的单核苷酸多态性(SNP)位点。本研究对鲤trim25基因多个拷贝的序列差异进行了比较,并对鲤与其他物种TRIM25的序列、进化关系和共线性相似度进行了比较,揭示了鲤trim25各拷贝间的结构多样性和在组织中的表达情况,筛选出了可能调控trim25基因表达的SNP位点,为今后研究鲤TRIM25相关的调控和抗病研究提供了理论依据。     

Epitheliocystis in fish

Epitheliocystis is a condition affecting the gills and skin of fish, which has been reported from more than 50 freshwater and marine species. It is caused by intracellular Gram-negative bacteria. Mortalities have been associated with epitheliocystis infections in cultured fish. This review provides an update of our current understanding of this condition, including characterization of the pathogen using immunohistochemical and molecular studies. In most fish species the epitheliocystis agent was negative to an antibody specific for chlamydial genus-specific lipopolysaccharide antigen. Recently, four epitheliocystis agents from four different fish species have been characterized using molecular analysis. While they all belong to the order Chlamydiales, in a lineage separate from the Chlamydiaceae, they are distinct organisms and similarity analysis showed that they had highest similarity values with other chlamydia-like bacteria isolated from various sources, including humans or pig. This confirms the high diversity and host specificity of the pathogen. Further molecular analysis should result in an increased understanding of this condition. To date the pathogen has not been cultured, making experimental studies difficult. High stocking densities, presence of nutrients, season, temperature and fish age have been identified as potential risk factors for the manifestation of this condition.     

食用鱼类甲醛本底含量研究初报

通过对56种海水鱼共计105个样品,16种淡水鱼共计19个样品的甲醛本底含量研究。结果发现,食用鱼类的甲醛本底含量不同且差异较大,海水活鱼与海水冷冻鱼的甲醛含量均显著高于淡水活鱼与淡水冷冻鱼（P〈0．01）;海水鱼中龙头鱼和鳕鱼类样品甲醛本底含量较高;大部分淡水鱼未检出甲醛;同一品种不同存活状态的鱼,其甲醛含量也不同,活体鱼中甲醛含量最低,冰鲜样品中甲醛含量最高,冷冻样品随着冻藏时间的延长甲醛含量呈现上升趋势。     

Phylogenetic analysis of noxious red tide flagellates Chattonella antiqua, C. marina, C. ovata, and C. verruculosa (Raphidophyceae) based on the rRNA gene family

ABSTRACT:   Four species of Chattonella , which are well known to form red tides that are lethal to fish, were subjected to phylogenetic analysis on the basis of the ribosomal RNA genes (rDNA), 5.8S rDNA, 18S rDNA, 28S rDNA, and the flanking internal transcribed spacers 1 and 2 (ITS1 and ITS2). The 18S rDNA sequences of C. antiqua , C. marina , and C. ovata isolated from different regions in Japan were compared. They were found to be identical with each other in a sequence 1818 bp long. The sequences of the D1/D2 region in the 28S rDNA, 5.8S rDNA, and ITS region that are known to be more variable regions were also found to be identical. These homogeneities of the rRNA gene family revealed the extremely close relatedness of C. antiqua , C. marina , and C. ovata . The sequences of C. verruculosa were different from those of these three species , resulting in an 89.2% homology in the 18S rDNA sequences, 70.4% homology in the D1/D2 region in the 28S rDNA sequences, and an 81.5% homology in 5.8S rDNA sequences and the ITS regions. Chattonella verruculosa was grouped within a single cluster composed of Dictyochophyceae rather than the other species of Raphidophyceae.     

Occurrence of postmortem myoliquefactive kudoosis in Atlantic mackerel, Scomber scombrus L., from the North Sea

Members of the myxosporean genus Kudoa occur in various marine teleosts worldwide. Several species are of concern to the fishery and aquaculture industries as they may produce unsightly cysts in the fish host's musculature or are associated with postmortem myoliquefaction of the fish muscle, commonly referred to as 'soft flesh'. This study describes the occurrence and effects on a host of a Kudoa species in Atlantic mackerel, Scomber scombrus , from the northern North Sea. Generalized postmortem myoliquefaction associated with Kudoa sp. occurred in 0.8% of the examined fish, i.e. 11 of 1339 mackerel developed 'soft flesh'. There was a significant difference in the prevalence of myoliquefaction between medium sized (400–600 g) and large mackerel (>600 g). The prevalence reached 8.9% in the latter host size group. No subclinical infections of Kudoa sp. were detected when examining fresh muscle ( n  = 103) and blood ( n  = 165) samples for spores using light microscopy. Affected mackerel developed generalized myoliquefaction after 38–56 h post-catch. No inflammatory host response was associated with the presence of plasmodia within single body muscle fibres of 'soft flesh' affected fish. Based on comparison of myxospore dimensions and analysis of the nuclear small subunit (SSU) ribosomal DNA, the present Kudoa species is assigned to Kudoa thyrsites . However, due to the species' apparently very wide geographical distribution and host range, its varying effect on different fish host species, together with the still unknown life cycle of Kudoa spp., the taxonomic status of K. thyrsites appears not to be fully resolved.     

5科11种鱼类ITS1特征分析及其在系统分类研究中的适用性

为了探讨ITS1作为分子标记用于鱼类系统演化的适用性,实验选取鲈形目5科11种鱼类为研究对象,包括尖吻鲈科、射水鱼科、军曹鱼科、剑鱼科和鲹科。通过克隆和测序等技术共获得了348条ITS1序列,长度范围为442~661 bp;通过对所有序列的长度、变异位点数量、GC含量、核苷酸多样性及单倍型多样性指数等遗传特征比较分析发现,11种鱼类ITS1序列无论是在种内还是在种间,长度和序列都表现出较为明显的多态性。特别是在军曹鱼中,70条克隆的长度范围为648~661 bp,但有一条序列存在55 bp缺失,结合该序列的GC含量,二级结构和最小自由能,推断该序列为假基因。以鮣为外类群,基于核糖体ITS1序列构建的邻接树显示在物种种类水平上,不同个体的克隆都按种类聚支,ITS1可以用于该类群物种的区分;在属级水平上,ITS1将11属鱼类完全区分开,能够用于属级水平的区分;在科级水平上,虽然鲹科分为2支的分子结果和形态分类存在差异,但ITS1构建的系统关系与线粒体分子标记构建的系统进化树相似。研究表明,核糖体ITS1可以作为一种有效的分子标记用于研究鱼类的系统分类研究,并且不同的分类阶元其解析能力不同,这将为鱼类核糖体的研究提供科学依据。