Female-biased operational sex ratio of sexual host fish in a gynogenetic complex of Carassius auratus

To study the coexistence of sexual and gynogenetic forms, we examined the population structure of a gynogenetic complex of the Japanese crucian carp, Carassius auratus Temminck et Schlegel, during the April–June reproductive season by collecting 1225 mature fish that migrated from Lake Suwa to a tributary river for spawning. There were more sexual fish (about 80%) than gynogenetic fish in this complex, and the operational sex ratio in the sexual form was female biased (males were about 20%). Mean standard length and body weight of sexual females were larger than those of sexual males. Sex ratio was male biased in smaller fish (standard length, <8.5 cm) but female biased in larger fish (standard length, ≥8.5 cm). We determined age by scale ring marks; the average age of sexual females was higher than that of males, but there was no significant difference in the average age between sexual and gynogenetic females. Sex ratio in the sexual form was more female biased for old than for young fish, and the mean size of sexual females was larger than that of males of the same age. The clear female-biased sex ratio and age difference between sexual females and males can be explained either by (1) higher mortality of males or by (2) female-biased sex allocation. The latter process reduces the disadvantage of sex and contributes to the coexistence of sexual and gynogenetic forms. Received: November 24, 2000 / Accepted: March 6, 2001     

Expression characterization of testicular DMRT1 in both Sertoli cells and spermatogenic cells of polyploid gibel carp

Dmrt1 has been suggested to play significant roles in sex determination and differentiation, but various expression patterns and cell types have been observed in the testis of vertebrates. Polyploid gibel carp, because of the multiple modes of unisexual gynogenesis and sexual reproduction, has become a unique case to explore the evolution of sex determination and differentiation. However, the sex-determination related genes in gibel carp have remained unknown. In this study, we identified and characterized 4 cDNAs of Dmrt1 genes. Subsequently, a polyclonal antibody specific to CagDMRT1 was prepared to examine its expression and distribution patterns at protein level. Significantly, both relative real-time PCR and Western blot detection confirmed predominant expression of CagDmrt1 in the adult testis of gibel carp. Moreover, the intensive expression of CagDMRT1 around spermatogenic cysts was revealed during spermatogenesis. And, following immunofluorescence co-localization of CagDMRT1 and CagVASA, a prominent CagDMRT1 expression in Sertoli cells and a mild CagDMRT1 expression in spermatogenic cells including spermatogonia and primary spermatocytes were clearly characterized. The CagDMRT1 signal in Sertoli cells is extensively distributed in both nuclei and cytoplasm, while the CagDMRT1 in spermatogonia and primary spermatocytes is mainly expressed in nuclei, and there is only the remained CagDMRT1 signal in the cytoplasm of secondary spermatocytes. These findings suggest that DMRT1 should be related to testis differentiation and spermatogenesis in gibel carp.     

Does Phaeocystis spp. contribute significantly to vertical export of organic carbon?

Phaeocystis spp. cell and colony mass fluxes and their contribution to the vertical particulate organic carbon (POC) export from a wide range of stations were quantified by short-term sediment traps. The compilation of available data, ranging from polar to sub-arctic and boreal regions, revealed that Phaeocystis colonial and single cells frequently are observed in shallow sediment traps at 30–50 m depth (average of 7 ± 11% of POC export). A strong vertical export decline between 40 m and 100 m diminished the contribution of Phaeocystis spp. cell carbon to vertical export of POC to only 3 ± 2% at 100 m depth, with two exceptions (deeper mixed stations). Estimates of potential corresponding mucus contribution increased the average Phaeocystis spp. contribution to <5% of POC export. The vertical flux attenuation efficiency is higher for Phaeocystis spp. than for diatoms. The overall contribution of Phaeocystis spp. to vertical carbon export based on direct investigations of vertical organic carbon export is small.     

重庆地区鲫外寄生车轮虫形态分类学研究及一新种的描述(英文)

在对重庆地区进行鱼类寄生虫学的调查过程中,从鲫鳃表获得3种隶属于车轮虫属Trichodina Ehrenberg,1830的外寄生车轮虫,其中含一新种,短棘车轮虫Trichodina brevicirra sp.nov,其典型的鉴别性特征为其短细的齿棘。另外两种车轮虫分别为沃玛车轮虫Trichodina ngoma Van As&Basson,1992与网状车轮虫Trichodina reticulata Hirschman&Partsch,1955;沃玛车轮虫为亚洲新记录种。文章对网状车轮虫的3种群进行了详尽的比较讨论研究,尽管该三种群间存在着细微的种群内差异,但网状车轮虫的典型特征则显而易见地存在于三种群间,即为附着盘中央具有8-16个球状或卵圆形的中央颗粒。       

Synapse-like contacts between axons of the pineal tract and the subcommissural organ in Rana perezi (Anra) and their absence in Carassius auratus (Teleostei): ultrastructural tracer studies

The present study was designed to investigate the controversial subject of the existence of a neural input from the pineal organ via the pineal tract to the subcommissural organ (SCO) in teleosts and anurans. Horseradish peroxidase was injected into the pineal organ and pineal tract of Carassius auratus and Rana perezi. Within the pinealofugal fibers the tracer was visualized at the light-and electron-microscopic levels either by immunocytochemistry using an anti-peroxidase serum, or by revealing the enzymatic activity of peroxidase. In both species, labeled myelinated and unmyelinated fibers of the pineal tract were readily traced by means of electron microscopy. In R. perezi, numerous terminals contacting the SCO cells in a synapse-like (synaptoid, hemisynaptic) manner bore the label, whereas a different population of endings was devoid of the tracer, indicating that in this species the SCO receives a dual neural input, one of pineal origin, the other of unknown source and nature. In the SCO of C. auratus, neither labeled nor unlabeled synapse-like contacts were found. Thus, in this latter species, a direct neural input to the SCO is missing. It is concluded that the secretory activity of the SCO can be controlled by different mechanisms in different species, and that more than one neural input mechanism may operate in the same species.     

An analysis of avoidance generalization and food preference transitivity in goldfish,Carassius auratus

To examine the effect of novelty in food selection by fishes, goldfish were trained by feeding them on red or green food pellets. Individual fish and fish in shoals of two, three, and five were then given a choice between equal numbers of familiar pellets and novel (yellow) pellets. In experimental groups, the yellow pellets were soaked in 15% quinine hydrochloride to make them unpalatable. Fish were next presented with equal numbers of familiar and a second novel pellet. It was expected that fish would generalize from their experience with the unpalatable pellets and demonstrate avoidance to sampling a second novel food item. However, as groups, neither controls nor experimentals were reluctant to sample the second novel pellets. Also, fish did not eat significantly more familiar than novel pellets when both were palatable. A third set of experiments examined food preference transitivity in which each pellet type was presented alone and in three pair-wise combinations to individual fish. Although red and yellow pellets were preferred over green, they were preferred equally, indicating an absence of transitivity in pellet choice and, perhaps, a “preference” for a mixture of red and yellow pellets.     

Twice Daily Melatonin Peaks in Siberian but not Syrian Hamsters under 24 h Light:Dark:Light:Dark Cycles

The daily pattern of blood-borne melatonin varies seasonally under the control of a multi-oscillator circadian pacemaker. Here we examine patterns of melatonin secretion and locomotor activity in Siberian and Syrian hamsters entrained to bimodal LDLD8:4:8:4 and LD20:4 lighting schedules that facilitate novel temporal arrangements of component circadian oscillators. Under LDLD, both species robustly bifurcated wheel-running activity in distinct day scotophase (DS) and night scotophase (NS) bouts. Siberian hamsters displayed significant melatonin increases during each scotophase in LDLD, and in the single daily scotophase of LD20:4. The bimodal melatonin secretion pattern persisted in acutely extended 16 h scotophases. Syrian hamsters, in contrast, showed no significant increases in plasma melatonin during either scotophase of LDLD8:4:8:4 or in LD20:4. In this species, detectable levels were observed only when the DS of LDLD was acutely extended to yield 16 h of darkness. Established species differences in the phase lag of nocturnal melatonin secretion relative to activity onset may underlie the above contrast: In non-bifurcated entrainment to 24 h LD cycles, Siberian hamsters show increased melatonin secretion within ～2 h after activity onset, whereas in Syrian hamsters, detectable melatonin secretion phase lags activity onset and the L/D transition by at least 4?h. The present results provide new evidence indicating multi-oscillator regulation of the waveform of melatonin secretion, specifically, the circadian control of the onset, offset and duration of nocturnal secretion.     

鲫幼鱼耳石荧光标记效果

为确认茜素络合物对鲫（Carassius auratus）耳石进行有效标记的可行性,以便为鲫甚至其他鲤科鱼类标志放流技术的开发及效果评估提供一定的借鉴,本研究以孵出后90 d的鲫幼鱼为研究对象,设置单一浓度（100 mg/L）的茜素络合物浸泡标记5 d,分析茜素络合物在耳石上的沉积情况以及不同耳石在不同后续饲养天数的动态变化。结果表明,矢耳石、微耳石和星耳石上在可见光、绿色和蓝色激发光下都检测到了良好的茜素络合物标记环,标记率和存活率均为100%。但不同耳石的茜素络合物标记效果不同,荧光下,星耳石的标记效果最显著,微耳石次之;可见光下,微耳石的标记效果最好,星耳石次之。随着后续饲养天数的延长,可见光下标记逐渐减弱,至20 d时基本消失,而在绿色和蓝色激光下标记环荧光强度无减弱迹象,能长久保持,且在蓝色激发光下标记环更易被观测到。上述结果结合鲫生长、存活和行为正常等情况综合显示,在100 mg/L茜素络合物溶液中浸泡标记鲫幼鱼5 d,其耳石可以获得满意的标记效果。     

三种淡水鱼类在中国南北两个地区的肠道菌群差异比较

山东省德州市禹城市和湖南省长沙市望城区分别属于我国北方和南方地区,环境和气候差异明显。本试验以禹城市和望城区两地的草鱼(Ctenopharyngodon idella)、鲫鱼(Carassius auratus)和鲤鱼(Cyprinus carpio)为研究对象,对肠道中的菌群进行16s rRNA V4高变区扩增,基于IonS5 TM XL测序平台进行测序,并对相关数据进行分析。结果表明,在门水平上鲫鱼、鲤鱼、草鱼的肠道优势菌主要为变形菌门(Proteobacteria)、梭杆菌门(Fusobacteria)、硬壁菌门(Firmicutes),拟杆菌门(Bacteroidetes),各组中这四种菌门所占比之和均在80%以上;基于Bray-Curtis距离值的秩次进行组间差异显著性检验,山东草鱼组和湖南草鱼组比较中组间差异大于组内差异(R=0.307,P<0.05),且线性判别分析显示湖南草鱼组的特征性菌群为弧菌属,而山东草鱼组的为梭菌纲,推测特征性菌群差异与环境的影响有关;有害菌种的统计分析表明,湖南鲫鱼组和鲤鱼组的嗜水气单胞菌属相对丰度明显高于对应的山东鲫鱼组和鲤鱼组,山东草鱼组和鲤鱼组的弧菌属相对丰度高于对应的湖南草鱼组和鲤鱼组,可能受外界环境的影响,不同地区抵御外来有害细菌的能力也不一样。本研究对两地的淡水鱼类肠道微生物群落结构进行了比较和分析,为进一步的鱼类发育研究奠定基础。     

The 65-kDa cytosolic protein associated with warm temperature acclimation in goldfish,Carassius auratus

Goldfish Carassius auratus were acclimated to either 10 or 30°C for a minimum of 5 weeks. A 65-kDa protein specific to warm-temperature-acclimated fish was extracted from the gel with 70% formic acid after two-dimensional electrophoresis of the muscle cytoplasmic protein fraction. The 65-kDa protein thus prepared to homogeneity was used to raise specific antibodies in rabbit by conventional methods. The antibody produced exhibited specific reaction with a protein having the same molecular weight from brain and liver tissue, suggesting that the 65-kDa protein is a ubiquitous cytosolic component in warm-acclimated goldfish. When water temperature was increased from 20 to 30°C over a 20-h period, a prominent amount of the 65-kDa protein was observed in muscle tissue extracts within 5 days of additional rearing; this was demonstrated by immunoblotting with the specific antibody. The N-terminal amino acid sequence of the 65-kDa protein was determined as Asp-Glu-Pro-Gln-Gly-His-Gln-His (or Asp)-Glu-Leu, differing from that of a family of known heat-shock proteins having about 70 kDa in molecular mass (hsp 70). No interaction between ATP and the 65-kDa protein revealed by ATP-agarose affinity chromatography further confirmed the different properties of the 65-kDa protein from those of hsp 70.Abbreviations ATP adenosine 5-triphosphate - hsp heat-shock protein(s) - IgG immunoglobulin G - mRNA messenger ribonucleic acid - PMSF phenylmethylsulphonyl fluoride - PVDF polyvinylidene difluoride - SDS sodium dodecyl sulphate - SDS-PAGE SDS-polyacrylamide gel electrophoresis