福建东张水库陆封型香鱼的遗传变异

测定了福建东张水库18尾陆封型香鱼的ND4-tRNA^Ser基因533 bp序列,发现2个可变位点和2个简约信息位点,共检测到4种单倍型。基于Kimura 2-parameter模型的遗传距离在0.001 9～0.003 9之间,在NJ系统树上无明显谱系结构;单倍型多样性(Hd)和核苷酸多样性(Pi)分别为0.627和0.001 37,平均核苷酸差异数为0.732,远低于两侧洄游型日本香鱼指名亚种(Hd为0.793,Pi为0.002 94),与被列为IUCN濒危物种名录的日本琉球香鱼亚种(Hd=0.519,Pi=0.001 11)相当。东张水库香鱼遗传多样性如此贫乏到底是历史原因还是近期陆封的结果,仍需进一步研究。目前亟待采取有效措施保护东张水库陆封香鱼。     

Indirect effects of the algivorous fish Plecoglossus altivelis altivelis on the growth of two insectivorous benthic fish

1. Animals exploiting different resources may nevertheless interact if one species indirectly alters the abundance and distribution of the food of the other. To analyse this indirect effect, we conducted experiments in artificial pools and in the field to investigate the influence of the algivorous fish Plecoglossus altivelis altivelis (known as the ayu) on two species of insectivorous benthic fish, Pseudogobio esocinus esocinus and the goby Gymnogobius petschiliensis .
2. In the pool experiments, algal biomass was not correlated with the number of ayu, but the percentage of blue-green bacteria rose as the number increased. The number of aquatic macroinvertebrates on the upper surface of ceramic tiles placed in the pool bed decreased as the number of ayu increased.
3. Although ayu and the benthic species did not interact directly, the reduction in invertebrate abundance on the upper surface of tiles in the pool reduced the growth rate of the benthic insectivores.
4. In field experiments, the introduction of ayu into habitats with P. esocinus esocinus or G. petschiliensis reduced the growth rate of these benthic fish. In the field experiment that was carried out over 5 years in the G. petschiliensis habitat, the population density of the goby decreased when ayu were stocked.
5. The ayu is a strong interactor or bioengineer in streams, affecting not only benthic algae but also aquatic invertebrates and fishes. We conclude that to predict the outcome of interspecific interactions amongst fishes in streams with high algal production, possible indirect effects must be considered alongside better known direct effects.     

长江下游发现香鱼的稚鱼

长江靖江江段位于长江最下游,接近河口段。在对这一江段沿岸的鱼类进行调查的过程中,发现在2004年5月11日的渔获物中,有1尾体长70.8mm、体重3．34g的香鱼（Plecoglossus altivelis）稚鱼。这是香鱼在长江流域的首次分布报道。     

Geographical continuity and discontinuity in the meristic characteristics of ayus of the southern subspecies Plecoglossus altivelis ryukyuensis

Ichthyological Research - Two subspecies of ayu, Plecoglossus altivelis altivelis (nominotypical subspecies) and P. a. ryukyuensis (Ryukyu-ayu), differ morphologically, behaviorally, and...     

Inheritance of amplified fragment length polymorphism markers and their utility in population genetic analysis of Plecoglossus altivelis

The reproducibility, mode of inheritance and polymorphism of amplified fragment length polymorphism (AFLP) markers were examined in ayu Plecoglossus altivelis (Salmoniformes: Plecoglossidae). The AFLP markers were highly reproducible, their inheritance following Mendelian expectations. The number of fragments amplified (34–134), polymorphic ratio (0·15–0·78) and average heterozygosity (0·02–0·25) of the AFLP markers showed significant variation among six primer pairs and among ayu populations, including a landlocked Lake‐Biwa population, two amphidromous populations ( P. a. altivelis ) and two Ryukyu‐ayu populations ( P. a. ryukyuensis ). Although AFLP analysis provided similar results in intra‐population diversity and relationships among populations to those found by analyses of allozymes, microsatellites and mitochondrial DNA sequences, AFLPs showed higher polymorphisms and hence greater distinction between genetically close populations.     

A new subspecies of the ayu,Plecoglossus altivelis, (Plecoglossidae) from the Ryukyu Islands

A new subspecies of the ayu,Plecoglossus altivelis ryukyucnsis, is described on the basis of specimens from Amami-oshima and Okinawa Islands, the Ryukyu Islands, Japan. This new subspecies is distinguished fromP. altivelis altivelis by the fewer numbers of pectoral fin rays, longitudinal scales and scales above and below the lateral line, and also by the unique electrophoretic mobilities of several enzymes.     

Occurrence and body size changes of drifting land-locked Ryukyu-ayu Plecoglossus altivelis ryukyuensis larvae in the San-numata River, Okinawa-jima Island, Japan

The occurrence and body size of drifting land-locked Ryukyu-ayu, Plecoglossus altivelis ryukyuensis, larvae were investigated in the San-numata River, Okinawa-jima Island from November 2000 to March 2001. The water temperature in the river fluctuated from 13.8 to 17.9°C during the sampling period. The drifting larvae occurred from mid-December to mid-March with an estimated spawning peak during late November and early December. The notochord length of the drifting larvae ranged from 4.9 to 6.7 mm (5.7 ± 0.3 mm, mean ± SD), and became longer as the spawning months progressed. These results imply that the land-locked population possesses the same maturation attributes as the original amphidromous population.     

Response to Sperm Penetration of the Cortex of Eggs of the Fish, Plecoglossus altivelis

The response of the egg to sperm penetration was examined in eggs of the fish, Plecoglossus altivelis , by scanning electron microscopy. Eggs responded to sperm penetration by forming a fertilization cone at a "sperm entry site", which is a specialized structure in the egg surface under the micropyle. Within one minute, the fertilization cone showed dramatic morphological changes from its earliest appearance, through full two-storied growth to its marked recession. The sperm entry site in the egg surface is discussed as a morphologically specialized organ responsible for the entrance of a fertilizing spermatozoon. The morphological characteristics of the egg and sperm are also described.     

Unexpected ceiling of genetic differentiation in the control region of the mitochondrial DNA between different subspecies of the ayu Plecoglossus altivelis

Sequence analyses of the non-coding, control region (CR) and coding region of the ND4-tRNA(Ser) genes in the mitochondrial DNA (mtDNA) were conducted for populations of the ayu Plecoglossus altivelis altivelis and the Ryukyu-ayu P. a. ryukyuensis. The level of genetic differentiation between the two subspecies evaluated from the CR data was substantially low, when comparing with that estimated from ND4-tRNA(Ser) gene region data, as well as those from nuclear genome data sets. By contrast, the differentiation between subspecies in the ND4-tRNA(Ser) gene region was substantial, being consistent with the results from the previous nuclear genome analyses. Results of UPGMA and minimum spanning network analyses also implied the unexpected ceiling of genetic differentiation in the CR. These results suggest that the CR does not reflect accurately the level of overall genetic differentiation between the populations of the ayu, but other coding regions of the mtDNA do reflect it so that the mtDNA on the whole may function as a rich source of useful markers for genetic assessment of populations of this species.     

Using dense locality sampling resolves the subtle genetic population structure of the dispersive fish species Plecoglossus altivelis

In dispersive species with continuous distributions, genetic differentiation between local populations is often absent or subtle and thus difficult to detect. To incorporate such subtle differentiation into management plans, it may be essential to analyse many samples from many localities using adequate numbers of high‐resolution genetic markers. Here, we evaluated the usefulness of dense locality sampling in resolving genetic population structure in the ayu (Plecoglossus altivelis), a dispersive fish important in Japanese inland fisheries. Genetic variability in, and differentiation between, ayu populations around the Japan–Ryukyu Archipelago were investigated in 4746 individuals collected from 120 localities by genotyping 12 microsatellite markers. These individuals represented the two subspecies of ayu, namely the Ryukyuan subspecies (Plecoglossus altivelis ryukyuensis) and both amphidromous and landlocked forms of the nominotypical subspecies (P. a. altivelis) along the archipelago. We successfully detected an absence of genetic differentiation within the landlocked form and subtle but significant differentiation and clear geographic patterns of genetic variation among populations of the amphidromous form, which had been considered genetically homogeneous. This suggests that dense locality sampling effectively resolves subtle differences in genetic population structure, reducing stochastic deviation in the detection of genetic differentiation and geographic patterns in local populations of this dispersive species. Resampling analyses based on empirical data sets clearly demonstrate the effectiveness of increasing the number of locality samples for stable and reliable estimations of genetic fixation indices. The genetic population structure observed within the amphidromous form provides useful information for identifying management or conservation units in ayu.     

Relation entre le frai du Labeo altivelis Peters et la conductivité des eaux

Summary In nearly all the rivers and streams of the Katanga province (Belgian Congo) several species of fisch migrate every year to their spawning-grounds. In some cases this spawning-run extends over more than 100 Km.Migration and reproduction take place at the time of the first rains or during a flood.In the Luapula-Mweru system, Labeo altivelis Peters took as spawning-ground a place where the water had at that moment a lower conductivity than elsewhere in the neighbourhood.

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Resume Au Katanga, plusieurs espèces de poissons effectuent chaque année des migrations tant dans les petites rivières que dans les grandes fleuves. Dans ces derniers les distances parcourues dépassent 100 Km.La migration et la fraie des poissons coïncident avec la crue des cours d'eau.Au Luapula, Labeo altivelis Peters va frayer dans des eaux qui ont une concentration basse par rapport à celles des autres parties du bassin.

     

香鱼甘油-3-磷酸脱氢酶基因的克隆与表达

GPDH(glycerol-3-phosphate dehydrogenase)是合成脂肪代谢中间产物甘油-3-磷酸的关键酶。通过设计简并引物从香鱼肝cDNA文库中克隆GPDH基因,该基因cDNA序列全长577个核苷酸,单一大的开放阅读框编码一个由351个氨基酸组成的分子量为37.9kD的蛋白。蛋白序列分析表明,香鱼GPDH(aGPDH)与亚洲胡瓜鱼的GPDH序列同源性最高。系统进化树分析表明,GPDH的物种进化关系与目前接受的物种分类关系基本一致。实时荧光定量PCR结果显示,aGPDH基因在香鱼肝、脾、肾、脑、心和肌肉组织均有表达。香鱼咸淡水适应以后,肝、脾、脑、心和肌肉的aGPDH的mRNA表达水平下调。成功构建重组表达质粒pET-32a-GPDH。SDS-PAGE试验表明,目的蛋白可以在大肠杆菌中大量表达;并制备了抗血清,能与目的蛋白起强的特异性反应,但不与细菌自身蛋白起反应。本研究有助于进一步理解鱼类盐度适应过程中的脂肪代谢调控机制。     

Monthly occurrence and feeding habits of larval and juvenile Ryukyu-ayu <Emphasis Type="Italic">Plecoglossus altivelis ryukyuensis</Emphasis> in an estuarine lake and coastal area of the Kawauchi River,Amami-oshima Island,southern Japan

We examined monthly occurrence patterns and feeding habits of larvae and juveniles of the critically endangered Ryukyu-ayu Plecoglossus altivelis ryukyuensis in the lower reach of the Kawauchi River, Amami-oshima Island, southern Japan, for two successive years. The study area was classified into a brackish lake (Lake Uchiumi) and a coastal zone (Sumiyo Bay) based on monthly variations in water temperature and salinity. Larvae and juveniles occurred from December to April in the first year and from January to February in the second year, respectively. Smaller-sized and earlier developmental-staged P. altivelis ryukyuensis individuals tended to emerge in larger numbers in Lake Uchiumi than in Sumiyo Bay. The present data suggest that Lake Uchiumi, where the physical environment is characterized by lower temperature and salinity than in Sumiyo Bay, would be suitable as a nursery ground for this fish, especially for earlier developmental-staged larvae. No individuals ≥25.0 mm body length, which is the size at which they begin their upstream migration, occurred in Lake Uchiumi or Sumiyo Bay in April or May, when upstream migration is assumed to reach a peak based on previous studies, in either year. The peak of upstream migration, therefore, may have occurred several months earlier in the years covered in this study due to higher water temperature than in typical years. To assess the feeding habits of this fish, the gut contents were observed. In both areas, copepods were abundant in P. altivelis ryukyuensis diet with calanoids and Oithona spp. being the most abundant. The diet composition differed between Lake Uchiumi and Sumiyo Bay and clearer ontogenetic variation in the composition of the diet was observed in Lake Uchiumi. Small individuals fed on tintinnid ciliates, but the proportion of these organisms in the diet gradually decreased with growth. Large individuals fed exclusively on harpacticoid copepods and insects including demersal species. Overall, larval and juvenile P. altivelis ryukyuensis exhibited a generalist feeding habit that tended to increase with growth. It is indispensable to adequately manage the environmental conditions in the lower reach of the Kawauchi River, especially Lake Uchiumi, to conserve P. altivelis ryukyuensis population.     

Efficacy of oral vaccine against bacterial coldwater disease in ayu Plecoglossus altivelis

The development of a practical vaccination method against bacterial coldwater disease (BCWD) in ayu Plecoglossus altivelis and the efficacy of oral administration of formalin-killed cells (FKCs) of Flavobacterium psychrophilum was investigated. The FKC was administrated at a dose of 0.1-0.2 g kg(-1) body weight to juvenile ayu (0.5 g body weight) every day for 2 wk or on 5 days over 2 wk. Experimental immersion challenge at 3 and 7 wk after vaccination showed significantly higher survival rates than the controls. The results show the effectiveness of oral vaccination against BCWD in ayu.     

Population genetic structure and effective population size of ayu (Plecoglossus altivelis), an amphidromous fish

The temporal and spatial population genetic structure of ayu Plecoglossus altivelis (Salmoniformes: Plecoglossidae), an amphidromous fish, was examined using analysis of variation at six microsatellite DNA loci. Intracohort genetic diversities, as measured by the number of alleles and heterozygosity, were similar among six cohorts (2001–2006) within a population (Nezugaseki River), with the mean number of alleles per cohort ranging from 11·0 to 12·5 and the expected heterozygosity ranging from 0·74 to 0·77. Intrapopulational genetic diversities were also similar across the three studied populations along the 50 km coast, with the mean number of alleles and the expected heterozygosity ranging from 11·33 to 11·67 and from 0·75 to 0·76, respectively. The authors observed only one significant difference in pair-wise population differentiation ( F _ST-value) between the cohorts within a population and among three populations. Estimates of the effective population size ( N _e) based on maximum-likelihood method yielded small values (ranging from 94·8 to 135·5), whereas census population size ranged from c. 4800 to 24 000. As a result, the ratio of annual effective population sizes to census population size ( N _e/ N ) ranged from 0·004 to 0·023. These estimates of N _e/ N agree more closely with estimates for marine fishes than that of the larger estimates for freshwater fishes. The present study suggests that ayu which is highly fecund and shows low survival during the early life stages is also characterized by having low value of N _e/ N , similar to marine species with a pelagic life cycle.     

Adherence of Flavobacterium psychrophilum on the body surface of the ayu Plecoglossus altivelis

Bacterial cold water disease in the ayu Plecoglossus altivelis caused by Flavobacterium psychrophilum is a serious problem in the Japanese freshwater culture industry. The distribution and activity of this bacterium on the body surface of the ayu in the infection process was investigated. The survival of F. psychrophilum in tap water showed that this bacterium might sustain its infectivity for 24 h. In an experimental infection, juvenile ayu were immersed in water containing 10(8.9) CFU/ml F. psychrophilum, and the progressing infection was followed by scanning electron microscopy during a 24-h period. This bacterium was observed in the ayu for 24 h adhering to the lower jaw and caudal peduncle, where the epidermis tissue was collapsed. This study showed that bacterial suspension in water sustains the activity of this bacterium. F. psychrophilum attaches especially to the jaw and caudal peduncle, growing at these sites, collapsing the dermal structure and invading the tissues.     

Gap junctions between microvilli of an oocyte and follicle cells in the teleost (Plecoglossus altivelis)

In the teleost, Plecoglossus altivelis, intercellular junctions between microvilli of an oocyte and follicle cells were studied by electron microscopy. Microvilli, which were radiated from an oocyte and arrived at the surface of follicle cells, established contact with follicle cells. These contact areas appeared to be a seven-layered membrane with an overall thickness of about 18 microns by standard fixation. In freeze-fracture replicas, many small aggregates of intramembraneous particles were revealed on the cleavage faces of cytoplasmic membranes of follicle cells. These morphological evidences suggest that in the teleost gap junctions exist between the oocyte and follicle cells, especially on the surface of follicle cells.     

香鱼hepcidin基因的克隆、序列分析及组织表达特征

Hepcidin是一类富含半胱氨酸的抗菌肽,在鱼类非特异性免疫中起重要作用,具有调节铁代谢的功能。该研究克隆了香鱼hepcidin基因cDNA序列,全长763个核苷酸,包含一个完整的开放阅读框,推测编码一个由85个氨基酸组成的相对分子质量为9.7k的多肽,N端24个氨基酸是信号肽序列。香鱼hepcidin的成熟肽序列由25个氨基酸组成,含有8个半胱氨酸,可形成4个分子内二硫键结构。系统进化树分析表明,hepcidin的物种进化关系与目前接受的物种分类关系基本一致,香鱼hepcidin位于鱼类hepcidin簇中,与大西洋鲑hepcidin的亲缘关系最近,达60%。香鱼hepcidin在肝脏中表达量最大,在脾、肾、心脏和肌肉中也有表达。实时荧光定量PCR(qRT-PCR)结果表明,鳗利斯顿氏菌(Listonella anguillarum)感染以后香鱼肝组织中hepcidin基因mRNA表达量显著增加,在12h增加了8.26倍。hepcidin基因可能在香鱼抗外界病原物感染过程中起重要作用。     

驼背鲈不同组织5种同工酶表达的差异

运用聚丙烯酰胺垂直梯度凝胶电泳法研究了驼背鲈(Cromileptes altivelis)6种组织(肌肉、心脏、肝脏、肾脏、脑、脾脏)中的5种同工酶(酯酶、乳酸脱氢酶、苹果酸脱氢酶、苹果酸酶、天门冬氨酸氨基转移酶),并对其同工酶位点及其酶谱表型进行了分析。结果表明,驼背鲈的5种同工酶系统具有不同程度的组织特异性。酯酶检测到3条酶带,由3个基因座位编码。乳酸脱氢酶检测到5条酶带,由3个基因座位编码,其中C位点具有组织特异性。苹果酸脱氢酶检测到3条酶带,由1个基因座位编码,6组织均有相同的3条酶带,组织差异性不显著,而且只发现了上清液型,线粒体型的苹果酸脱氢酶没有发现。苹果酸酶有4条酶带,由2个基因座位编码。天门冬氨酸氨基转移酶在6种组织都有发现,只有一条酶带。     

Oral ontogeny of the Ayu, Plecoglossus altivelis and comparisons with the jaws of other salmoniform fishes

The Japanese Ayu, Plecoglossus altivelis Temminck & Schlegel is the sole representative of the salmoniform family Plecoglossidae. The Ayu is remarkable for its dentition which in adults comprises groups of diagonally arranged comb-like teeth in the outer tissue of the jaws. In juveniles (below 63 mm SL) the teeth are attached normally to the jaws. The transition of tooth form is correlated with a switch from zooplanktivory to algal or aufwuchs grazing. The present study follows the development of the teeth, jaws, oral cavity ethmoid and suspensorial elements in specimens ranging in size from 41–70 mm SL. The possible mode of function of the adult dentition is discussed. Comparisons are made with the jaws of other salmoniform fishes and a suite of supposed apomorphic characters are identified which are also shared with certain genera of the family Osmeridae, thus supporting the ideas of others that the Osmeridae is a paraphyletic assemblage.