PLANKTON AND SESTON STRUCTURE IN A SHALLOW, EUTROPHIC SUBTROPICAL CHINESE LAKE

The seasonal dynamics in the nutrient concentrations, chlorophyll-a amount (Chl-a), total algal volume (CV), Chl-a/CV ratio, seston structure were studied at two sampling stations in a shallow, highly eutrophicated subtropic lake (the Guozheng Hu area of the East Lake) on the plain of the middle basin of the Chang Jiang (the Yangtze River) of China. The lake ecosystem of the Guozheng Hu area is dominated by two planktivorous fishes (silver carp and bighead carp), phytoplankton and zooplankton. Macrophytes are extremely scarce in this area. Concentrations of the total dissolved nitrogen and phosphorus in the Guozheng Hu area in 1990 were very high. Fish yield, of which, more than 90 % was composed of silver carp and bighead carp in the Guozheng Hu area was very high (ca. 1140 kg/ha or 45.6 g/m3 in 1990). Grazing pressure by the fishes on the plankton community is considered to be rather strong. The annual average biomass of zooplankton was ca. 1/3 - 1/2 that of phytoplankton. On the average, dry matter in the living plankton only constituted ca. 3-7 % of the total dry seston, and plankton carbon only constituted ca. 5 - 10 % of the seston carbon. The present results indicate that, in the Guozheng Hu area of the East Lake, of the organic part of the seston, detritus is quantitatively an important constituent, while living plankton is only a very small component.

鰋鮡鱼类(Glyptosternoid fishes)的系统进化和动物地理学研究

鰋鮡鱼类共包括9 属43 种（亚种），隶属于鲇形目（Siluriformes）鮡科 （Sisoridae）鰋鮡亚科（Glyptosternae）中鰋鮡族（Tribe Glyptosternini）的鰋鮡 亚族（Subtribe Glyptosternina）。鰋鮡鱼类形态上的共同特征为：无胸吸着器，胸、 腹鳍水平展开，第一根鳍条完全分节或在外缘生出许多软骨细条，被外表皮所裹， 在腹面看到的是许多与分节或软骨细条大致对应的横纹皱褶。鰋鮡鱼类集中分布 于青藏高原周边的水系中，部分属种向西分布到了中亚地区的阿姆河上游，是适 应山区急流环境的一群鱼类。近年来一系列的研究表明，鰋鮡鱼类为一单系类群， 它的起源和演化与青藏高原的隆升有着直接的关系。鰋鮡鱼类的系统发育研究， 可以为青藏高原隆升的年代、幅度和形式提供间接的证据，其系统发育树的拓扑 结构也直接反映了东喜马拉雅地区诸水系的形成与演变。 本研究对鰋鮡鱼类9 属进行了系统整理。1. 发现并描述了异齿鰋属 （Oreoglanis）两新种，分别为分布于景东无量山（澜沧江水系）的景东异齿鰋 （O. jingdongensis）和分布于怒江水系南景河和南滚河的无斑异齿鰋（O. immaculatus）。认为分布于中国的异齿鰋属鱼类均属于尖须异齿鰋种组（O. siamensis species group）。指出区分异齿鰋属两个种组：尖须异齿鰋种组和细尾 异齿鰋种组（O. delacouri species group）的特征是下唇中部是否具有中央缺刻， 尾型的差别（新月型尾或凹型尾）不能用来区分两个种组，给出了异齿鰋属的检 索表，并绘制了异齿鰋属鱼类分布图。2. 对鮡属（Pareuchiloglanis）鱼类进行了 系统整理，通过外部形态度量性状的比较，认为分布于澜沧江水系的，曾经被鉴 定为扁头鮡（P. kamengensis）的标本，应属于大鳍鮡（P. macropterus），扁头鮡 和大鳍鮡之间的最明显的差别在于腹鳍前长的不同。前者的腹鳍前长为体长的 53.2-64.9%，后者的腹鳍前长均不达体长的50%。3. 通过比较金沙江水系分布的 5 种鮡属鱼类，中华鮡（P. sinensis）、前臀鮡（P. anteanalis）、壮体鮡（P. robusta）、 四川鮡（P. sichuanensis）和天全鮡（P. tianquanensis），认为天全鮡和四川鮡之 间分布水系重叠，外部形态亦无差别，天全鮡很可能为四川鮡的同物异名。给出 了鮡属鱼类的系统检索表，并绘制了鮡属鱼类分布图。利用分子系统学的原理和方法对鰋鮡鱼类进行系统发育研究。测定了6 属 15 种鰋鮡鱼类和鮡科中非鰋鮡鱼类4 属7 种共28 个体的线粒体Cyt b 基因部分 片段和全序列（1138 bp），结合从GenBank 下载的相关类群相同的基因序列，以 魾属（Bagarius）的巨魾（B. yarrelli），纹胸鮡属（Glyptothorax）的穴形纹胸鮡 （G. cavia）、亮背纹胸鮡（G. dorsalis）、扎那纹胸鮡（G. zainaensis），福建纹胸 鮡（G. fukiensis fukiensis）、海南纹胸鮡（G. fukiensis hainanensis），黑鮡属（Gagata） 的长丝黑鮡（G. dolichonema）以及褶鮡属（Pseudecheneis）的黄斑褶鮡（P. sulcatus） 和无斑褶鮡（P. immaculatus）作为外类群，采用贝叶斯法（Bayesian）、最简约 法（maximum pasimony, MP）和邻接法（neighbour-joining, NJ）构建系统发育树。 结果显示： 1. 鰋鮡鱼类为一单系类群，并且与褶鮡属互为姐妹群关系； 2. 原鮡属、鰋属和凿齿鮡属是鰋鮡鱼类的三个基部类群； 3. 异齿鰋属构成为一个单系群，大鳍异齿鰋最早从该属的基部分化出来； 4. 石爬鮡属构成一个单系，并与分布于金沙江水系的中华鮡＋前臀鮡构成姐妹 群，黄石爬鮡和青石爬鮡的单倍型相互交错；显示两个物种的分类是不合适的， 而是同一水系不同支流种群之间梯度变异的例子，依据本次研究所得出的三个分 支图，结合青石爬鮡自西至东分布于金沙江、雅砻江、大渡河、青衣江、岷江等 的分布格局以及形态特征的分布，显示形态特征的分布变化有以下趋势：自西至 东，腹鳍位置逐渐前移；颌须渐趋缩短；胸鳍趋向发达、伸达腹鳍起点。这些变 化趋势是同一水系不同支流种群之间梯度变异的极好例子； 5. 分布于澜沧江以西（包括澜沧江）水系的鮡属鱼类（扁头鮡、细尾鮡、短鳍 鮡）与分布于怒江和伊洛瓦底江水系的拟鰋属鱼类构成为一支，并且二者共同与 分布于元江上游（红河水系）的大孔鮡构成为单系。其中，短体拟鰋和拟鰋互为 姐妹种；而扁头鮡和短鳍鮡也互为姐妹种；细尾鮡的系统地位则尚不能确定； 6. 无论在MP 树、贝叶斯树还是NJ 树中，石爬鮡属、鮡属、拟鰋属和异齿鰋属 构成一个单系，并且支持率达到了100％。 7. 鰋属位于鰋鮡鱼类的基部，是较早就从鰋鮡鱼类祖先中演化出来的一个类群， 鰋类的口吸盘是一个趋同性状，是在急流环境条件下形成的一种适应性性状，在 鰋类各属中不是同源特征； 8. 鮡属鱼类不是一个单系类群，分布于金沙江流域的鮡属鱼类与同流域分布的石爬鮡属鱼类聚成一支；澜沧江及其以西水系分布的鮡属鱼类与同流域分布的拟 鰋属鱼类聚成一支，之后这两支又同异齿鰋属共同构成为一个大支。 结合鰋鮡鱼类的系统发育分支图对其动物地理学进行研究。鰋鮡鱼类是由类 似纹胸鮡属（Glyptothorax）鱼类的祖先演化而来，鰋属（Exostoma）和凿齿鮡 属（Glaridoglanis）是较早就从从类似原鮡的祖先中演化出来，鮡属、石爬鮡属、 拟鰋属和异齿鰋属这一大支由类似原鮡的祖先演化而来。在青藏高原强烈隆起等 重大地理隔离事件发生之前，类似于现生的原鮡属鱼类已经广布喜马拉雅山脉东 西两侧。在青藏高原强烈隆起等重大地理隔离事件发生后，鰋鮡鱼类在相同的地 理隔离下独自演化为现在的分布格局。

Determination of photochemically produced hydroxyl radicals in seawater and freshwater

A variety of short-lived, reactive chemical species (i.e. free radicals and excited state species) are known to be photochemically produced in natural waters. Some of these transients may strongly affect chemical and biological processes, and they have been implicated in the degradation of organic pollutants and natural organic compounds in aqueous environments. Previous studies demonstrated that the highly reactive hydroxyl radical (OH) is photochemically formed in seawater. However, the quantitative importance of this key species in the sea has not been previously studied because of past analytical limitations. By using a highly sensitive probe based on α-H atom abstraction from methanol, we were able to measure production rates and steady-state concentrations of photochemically produced OH radicals in coastal and open ocean seawater and freshwaters. The validity of the method was tested by intercalibrating with an independent, OH-specific reaction, hydroxylation of benzoic acid, and also by competition kinetics experiments. Our OH production rates and steady-state concentrations for freshwaters are in excellent agreement with those measured by previous investigators for similar waters. In contrast, for seawater, the values we measured are 1–3 orders of magnitude higher than previously predicted by models, indicating that there is a major unknown photochemical OH source (s) in seawater.

Electrochemical measurement of hydrogen peroxide in plasma: Evaluation of freshwater prawn (Macrobrachium rosenbergii) and crucian carp (Cyprinus carpio) phagocytes under natural conditions

An electrochemical technique for the real-time detection of hydrogen peroxide (H2O2) was employed to describe respiratory burst activity (RBA) of phagocytes in plasma which can be used to evaluate the ability of immune system and disease resistance. The method is based upon the electric current changes, by redox reaction on platinum electrode of extracellular hydrogen peroxide (H2O2) released from phagocytes stimulated by the zymosan at 680 mV direct current (d.c.). Compared with the control, activation of respiratory burst by zymosan particles results in a high amperometric response, and a current peak was obtained during the whole monitoring process. The peak current was proved by addition Of Cu2+ and other controls, to be the result of intense release of H2O2 from phagocytes. The peak area was calculated and used to evaluate the quantity of effective H2O2, which represents the quantity of H2O2 beyond the clearance of related enzymes in plasma. According to Faraday's law, the phagocytes' ability of prawns to generate effective H2O2 was evaluated from 1.253 x 10(-14) mol/cell to 6.146 x 10(-14) mol/cell, and carp from 1.689 x 10(-15) Mol/Cell to 7.873 x 10(-1)5 mol/cell. This method is an acute and quick detection of extracellular effective H2O2 in plasma and reflects the capacity of phagocytes under natural conditions, which could be applied for selecting species and parents with high immunity for breeding in aquaculture. (c) 2007 Elsevier Ltd. All rights reserved.

Population genetics of Crassostrea ariakensis in Asia inferred from microsatellite markers

Crassostrea ariakensis is an important aquacultured oyster species in Asia, its native region. During the past decade, consideration was given to introducing C. ariakensis into Chesapeake Bay, in the United States, to help revive the declining native oyster industry and bolster the local ecosystem. Little is known about the ecology and biology of this species in Asia due to confusion with nomenclature and difficulty in accurately identifying the species of wild populations in their natural environment. Even less research has been done on the population genetics of native populations of C. ariakensis in Asia. We examined the magnitude and pattern of genetic differentiation among 10 wild populations of C. ariakensis from its confirmed distribution range using eight polymorphic microsatellite markers. Results showed a small but significant global theta (ST) (0.018), indicating genetic heterogeneity among populations. Eight genetically distinct populations were further distinguished based on population pairwise theta (ST) comparisons, including one in Japan, four in China, and three populations along the coast of South Korea. A significant positive association was detected between genetic and geographic distances among populations, suggesting a genetic pattern of isolation by distance. This research represents a novel observation on wild genetic population structuring in a coastal bivalve species along the coast of the northwest Pacific.

Effects of cold shock on microtubule organization and cell cycle in gynogenetically activated eggs of olive flounder (Paralichthys olivaceus)

Cytological changes and subsequent mitotic processes were studied in gynogenetically activated eggs of olive flounder subjected to cold-shock treatment using indirect immunofluorescence staining of isolated blastodisks. Obvious differences between controls and treated eggs were detected during early cell division. The developmental process of haploid control was similar to that of the diploid control except several minutes delayed. Spindles disassembled by the cold-shock treatment regenerated soon after treatment, resulting in the occurrence of the first mitosis. The immature daughter centriole was easily depolymerized by cold-shock treatment, leading to the formation of the bipolar spindle in the first cell cycle and the formation of the monopolar spindle in the second cell cycle, resulting in chromosome set doubling. Some two-cell stage eggs had a monopolar spindle in one blastomere and a bipolar spindle in another during the second mitosis. These eggs had a high potency developing into haploid-diploid mosaics. To the best of our knowledge, this study is the first to clarify the mechanism of chromosome set doubling in marine fishes and provides a preliminary cytological basis for developing a reliable and efficient protocol for mitotic gynogenesis induction by cold-shock treatment in olive flounder.

Interbasin freshwater, heat and salt transport through the boundaries of the East and South China Seas from a variable-grid global ocean circulation model

The monthly and annual mean freshwater, heat and salt transport through the open boundaries of the South and East China Seas derived from a variable-grid global ocean circulation model is reported. The model has 1/6degrees resolution for the seas adjacent to China and 30 resolution for the global ocean. The model results are in fairly good agreement with the existing estimates based on measurements. The computation shows that the flows passing through the South China Sea contribute volume, heat and salt transport of 5.3 Sv, 0.57 PW and 184 Ggs(-1), respectively (about 1/4) to the Indonesian Throughflow, indicating that the South China Sea is an important pathway of the Pacific to Indian Ocean throughflow. The volume, heat and salt transport of the Kuroshio in the East China Sea is 25.6 Sv, 2.32 PW and 894 Ggs(-1), respectively. Less than 1/4 of this transport passes through the passage between Iriomote and Okinawa. The calculation of heat balance indicates that the South China Sea absorbs net heat flux from the sun and atmosphere with a rate of 0.08 PW, while the atmosphere gains net heat flux from the Baohai, Yellow and East China Seas with a rate of 0.05 PW.

Evolution of freshwater plumes and salinity fronts in the northern Bay of Bengal

[1] The evolution of freshwater plumes and the associated salinity fronts in the northern Bay of Bengal ( henceforth the bay) is studied using rotated empirical orthogonal function (REOF) analysis and extended associate pattern analysis (EAPA). The results show that sea surface salinity distribution is featured by eastern-bay and western-bay plumes in the northern bay during different seasons. The western-bay plume begins in early July, peaks in late August, and then turns into a bay-shaped plume with the two plumes in either side of the bay, which peaks in late October. The southward extension of the western-bay plume can be explained by the southwestward geostrophic flow associated with the cyclonic gyre in the northern bay, which counters the northeastward Ekman drift driven by wind stress. The offshore expansion of the western-bay plume is induced by the offshore Ekman drift which also produces a salinity front near the east coast of India. The bay-shaped plume appears when the cyclonic gyre shifts westward and a weak anticyclonic gyre occupies the northeastern bay. As the season advances, the western part of the bay-shaped plume decays while the eastern part persists until the following June, which is believed to be associated with the anticyclonic gyre in the northern bay. The evolution of the plumes except the eastern part of the bay-shaped plume in fall can be partly explained by the seasonal variation of mass transport associated with the Sverdrup balance. The fact that the western-bay (eastern-bay) plume appears when surface freshwater flux in the northeastern bay increases ( decreases) dramatically suggests that the plumes are not produced directly by surface freshwater flux. River discharge seems to be the freshwater source for the plumes and has little to do with the evolution of the plumes.

Feeding, morphological changes and allometric growth during starvation in miiuy croaker larvae

We investigated the effects of the timing of first feeding (larvae in F0, F1, F2, F3 and S were first fed on day 3, 4, 5, 6 days after hatching (DAH) and unfed, respectively) on feeding, morphological changes, survival and growth in miiuy croaker larvae at 24A degrees C. The fed larvae initiated feeding on 3 DAH and reached point of no return (PNR) on 6 DAH. Larvae in F0 and F1 groups survived apparently better than F2 group at the end of the experiment on 36 DAH. High larval mortality occurred from 3 to 7 DAH in all feeding groups, accounting for 40% (F0, F1 and F2 groups) to 90% (F3 and S groups) of the total mortality. Larvae in F0 and F1 groups grew better than F2 group throughout the experiment. Eye diameter, body height, head height and mouth gape of the first feeding larvae were more sensitive to starvation than other morphometrics and could be used as indicators for evaluating their nutritional status. Results indicated that delayed first feeding over 1 day after yolk exhaustion could lead to poor larval survival and growth. To avoid starvation and obtain good growth in culturing, larvae feeding should be initiated within 1 day after yolk exhaustion at 24A degrees C.