我国3个新记录海链藻种类的形态学研究

利用光镜(LM)和扫描电镜(SEM)技术,对采自我国沿海海域的自然水样,以及分离获得的单克隆培养藻株进行了形态学观察,针对其中的海链藻属Thalassiosira Cleve种类开展了形态分类学的专题研究。报道了3个新记录种类,分别是安达曼海链藻Thalassiosira andamanica Gedde、缢缩海链藻Thalassiosira con-stricta Gaarder和双线海链藻Thalassiosira duostra Pienaar。对每个种类的形态学特征、生活习性和生态分布进行了描述,提供了光镜和电镜照片,并对相似种类的形态学特征进行了比较研究。     

小字海链藻双卫变种,海链藻属一新变种

采用毛细管复洗技术建立海链藻属(Thalassiosira)物种的单克隆培养株系,结合形态学和分子系统学研究,对小字海链藻原变种(Thalassiosira minuscula var.minuscula Krasske)的形态特征进行观察,并报道了1个新变种:小字海链藻双卫变种(T.minuscula var.bicustodis X.H.Guo,Y.Q.GuoY.Li)。双卫变种与原变种的形态特征基本一致,区别仅在于唇形突的伴生支持突数目不同,双卫变种具有2个,原变种只有1个。基于对多个株系生活史的连续观察,确认其伴生支持突的数目稳定,具有分类学意义。     

光滑侧链藻——中国淡水硅藻新记录

2004-2006年,对武汉东湖的底栖藻类进行了生态学调查研究.在对底栖硅藻的定性和定量研究中,发现了一种中心纲种类为中国新记录,它具有一些海洋角盘藻科种类的特征,如眼纹斑(Ocellus)等.经鉴定为光滑侧链藻Pleurosira laevis(Ehrenberg)Compere.参考Compere 1982年的研究,我们同意他的看法,即以前在我国台湾发现的台湾多变筒藻Proteucylindrus taiwanensis Li et Chiang和广东发现的Cerataulus laevis var.?chinensis Grunow也应归于侧链藻属(Pleurosira),名称为索科特拉侧链藻Pleurosira socotrensis(Kitton)Compere.     

海链藻属重要形态学特征的二次研究——以艾伦海链藻为例

海链藻属（Thalassiosira Cleve）是硅藻门中物种多样性最为丰富的大属之一,广泛分布于全球各类水体。目前沿用的海链藻属分类体系是基于形态特征建立的,尤其是电镜下的超微特征具有重要的分类价值。然而,也有研究认为某些形态特征存在不稳定或变化的情况,应对其开展二次研究和重新评估。故此,本文选择全球近岸广布种艾伦海链藻（T.allen Takano）作为典型代表,基于建立的单克隆培养株系,结合传统形态学方法和现代分子生物学技术,对其重要形态特征进行了二次研究。结果显示：（1）艾伦海链藻壳面孔纹的排列方式存在一定的变化,呈切线形或偏心状;壳缘唇形突的位置多有变化,占据一个壳缘支持突的位置、或位于两个壳缘支持突正中间、或靠近其中一个。艾伦海链藻这两个特征并不具有较高的稳定性,其分类学意义或应降低;（2）壳缘不具有肋纹,此特征相对稳定,可作为艾伦海链藻的识别特征之一;（3）艾伦海链藻具有较保守的遗传多样性,尚未发现（拟）隐形种。结合其它海链藻的形态学报道,我们认为孔纹排列方式易受环境的影响,稳定性较差,在分类时应慎重应用;壳缘唇形突的位置在少数海链藻属物种中易发生变化,分类时应视具体物种而针对性应用;支持突等突起特征较为稳定,在海链藻属物种的分类体系中仍可作为重要依据;艾伦海链藻中壳缘肋纹具有较好的稳定性,可作为分类依据,但在其它海链藻属物种中是否也具有很好的分类价值,还需要更多的研究加以验证;分子信息在形态特征上的二次研究和评价中具有重要应用价值,但目前相关分子数据的缺乏和不足限制了对其进一步的研究。本研究对重新评估艾伦海链藻形态特征的分类学价值、完善现存的分类学体系提供了参考。     

海链藻属一新变种艾伦海链藻肋纹变种

为了澄清海链藻属Thalassiosira的物种多样性, 采用毛细管复洗技术建立了单克隆培养株系。利用光镜和扫描电镜观察形态学特征, 并扩增其核糖体小亚基和大亚基序列, 用于分子系统树的构建。结合形态学和分子系统学数据, 发现艾伦海链藻株系之间存在一定的形态差异和遗传多样性。经过与原始文献的比对, 确认了艾伦海链藻原变种的特征, 并报道了该种的一个新变种艾伦海链藻肋纹变种Thalassiosira allenii var. striata X. H. Guo, Y. Q. Guo & Y. Li。该变种与原变种的形态特征基本相似, 区别在于壳面边缘具有肋纹结构, 原变种则无。基于核糖体小亚基和大亚基的系统树均显示, 肋纹变种与原变种聚在同一个分支上, 形成姐妹支(BPP>0.90), 表明两者之间具有最近的亲缘关系。2个变种的核糖体小亚基序列完全一致, 没有碱基差异。但用于分析的556个核糖体大亚基序列中, 两者存在11个差异碱基, 遗传距离为0.01。     

我国新记录海链藻属物种的形态学和系统学研究

为了廓清我国海链藻属的物种多样性, 并丰富其分子生物学信息, 为后续的系统学研究提供基础数据, 从我国沿海分离并建立了海链藻的单克隆培养株系, 利用光学显微镜和电镜技术进行了形态学研究, 同时还对其核糖体大亚基的高变区序列进行了扩增和测序分析。结合形态学和分子生物学数据, 鉴定了我国海链藻属的2个新记录种: 狭线形海链藻Thalassiosira anguste-lineata (Schmidt) Fryxell & Hasle和碟形海链藻T. minicosmica Lee & Park。对它们的形态学特征进行了较为详尽的描述, 并与相似种进行了比较研究。此外, 还基于核糖体大亚基高变区的碱基序列信息, 分析了它们的分子系统学位置。在分子系统树上, 狭线形海链藻和碟形海链藻均不与该属模式种——诺氏海链藻T. nordenskioeldii 聚在同一分支上, 显示它们与典型海链藻属物种之间具有较大的遗传差异。分子系统树还显示, 目前基于形态学建立的海链藻属并非自然类群, 而是被骨条藻属Skeletonema、小环藻属Cyclotella、漂流藻属Planktoniella等邻近属种分隔成多个分支, 这预示着现存的海链藻属应该是一个并系类群, 在后续的系统学研究中, 或许会有较大的系统学调整, 但目前有限的分子生物学信息是相关研究推进的重要限制。     

采自广东大亚湾水域的海链藻属一新种——扇形海链藻

为澄清广东大亚湾水域海链藻属的物种多样性, 研究建立了它的单克隆培养株系。结合光镜和扫描电镜下的形态学特征, 以及基于核糖体大、小亚基序列的分子系统发育分析, 报道了中国海链藻属的1个新种, 即扇形海链藻Thalassiosira flabellata sp. nov. X.H. Guo, Y.Q. Guo & Y. Li。该种以短链状群体或单细胞生活, 壳面具有一圈壳缘支持突、一个中央支持突和一个壳缘唇形突。壳面孔纹束状排列, 是此种的典型特征。此种与帕尔海链藻T. partheneia较为相似, 区别特征如下: 此种的壳面支持突和唇形突均具有外管, 而帕尔海链藻的突起没有外管, 只有内管; 其次, 此种的壳面较平, 而帕尔海链藻的壳面隆起呈鼓状; 第三, 此种的中央支持突具有3个围孔, 而帕尔海链藻具有4—5个围孔。     

中国沟胸步甲属分类研究及一新种描述(鞘翅目： 步甲科： 壶步甲族)

【目的】沟胸步甲属Holcoderus属于鞘翅目(Coleoptera)步甲科(Carabidae)壶步甲族(Lebiini)。本研究旨在对该属在中国分布的各个种进行分类厘定。【方法】基于中国科学院动物研究所的馆藏标本以及欧洲多家博物馆的模式标本,采用形态比较学方法开展研究。【结果】共发现中国沟胸步甲属5种,其中包括新种1种(双毛沟胸步甲H. bisetus sp. n.,模式产地：云南西双版纳),中国新纪录种3种(雅沟胸步甲H. gracilis、绿沟胸步甲H. smaragdinus和红腿沟胸步甲H. aeripennis)。提供了中国所有种类的形态描述及特征图,并编制了分种检索表。【结论】至此,我国所分布的沟胸步甲属物种从此前记录的1种增加至5种。     

我国沿海闭合突海链藻的形态学研究

闭合突是一类特殊的突起, 仅报道于少数海链藻种类, 其形态学特征和排列方式是重要的分类学依据。我国关于闭合突海链藻的报道较少。研究利用扫描电镜(SEM)技术, 对采自我国沿海海域的自然水样, 以及分离获得的单克隆培养藻株进行了形态学观察, 针对其中的海链藻属Thalassiosira Cleve种类开展了形态分类学的专题研究。报道了5个具有闭合突的海链藻种类, 分别是西达礁海链藻T. cedarkeyensis Prasad、偏心海链藻T. eccentrica (Ehrenberg) Cleve、伦德海链藻T. lundiana Fryxell、细孔海链藻T. punctigera (Castracane) Hasle和管状海链藻T. tubifera Fryxell, 其中有3个为我国新记录种类: 西达礁海链藻、细孔海链藻和管状海链藻。对每个种类的形态学特征和生境进行了描述, 提供了扫描电镜照片, 对相似种类的形态学特征进行了比较研究, 分析了突起特征的变化类型及其分类学价值。       

珠三角河网链状硅藻物种组成及生态特征

珠三角河网水域是珠江之水流入南海的必经之地,于2012年和2015年对该水域的链状硅藻的时空特征及其影响因素进行了分析。共发现链状硅藻18种(包括变种和变型),颗粒沟链藻是该水域的绝对优势种,也是该区域水体富营养化的重要指示物种。总生物量的时间变化模式呈现枯水期差异较大,丰水期差异较小的特点,主要是受到径流量、透明度和水温差异的影响;空间特征主要表现为广州市周边站位的生物量明显偏高,主要受水体富营养化的影响。不同链状硅藻的相对百分组成显示,颗粒沟链藻是绝对优势种,变异直链藻易在枯水期与其形成竞争优势。沟链藻属的链长一般大于直链藻属,这主要得益于其形态结构较稳固的优势;此外,透明度、营养盐和pH值等也是影响链长的重要因素。     

Aulacoseira calypsi sp. nov. (Coscinodiscophyceae) from an Amazonian lake,northern Brazil

This paper describes a new diatom species, Aulacoseira calypsi Tremarin, Torgan & Ludwig, from specimens in plankton samples from Água Preta lake. This Amazonian lake is a shallow mesotrophic environment situated in northern Brazil. The species is characterized by long filaments united by spatulate linking spines, obovate to conic separation spines, a valve surface variably ornamented, straight striae on the mantle, a narrow ringleist, and one row of sessile rimoportulae near the ringleist. Aulacoseira calypsi's morphometric features are compared with the following similar species: Aulacoseira nygaardii (Camburn) Camburn & Charles, Aulacoseira lacustris (Grunow) Krammer, Aulacoseira coroniformis Pearce & Cremer, Aulacoseira occulta Siver & Hamilton, Aulacoseira lancea Siver & Hamilton, Aulacoseira gessneri (Hustedt) Simonsen, and Aulacoseira islandica (Müller) Simonsen. The species shares similarities as to frustule size, striation pattern, and narrowness of ringleist; but differs in the morphology of separation and linking spines, and the number and position of the rimoportulae.     

Morphological variability of Aulacoseira granulata (Ehr.) Simonsen (Bacillariophyceae) in the Lower Paraná River (Argentina)

In this paper we consider the morphological variation within a natural population of Aulacoseira granulata (Ehr.) Simonsen in relation to environmental factors. This species was dominant in the phytoplankton of the Lower Paraná River (Argentina) and exhibited seasonal fluctuations of cell dimensions. The mean cell diameter was directly correlated with the river water level and inversely with pH and nitrate concentrations, whereas cell length was directly correlated with transparency and nitrate concentration and inversely with suspended solids. This pattern was similar to that observed for filament length. The cell length : diameter ratio was inversely related to water level and discharge and directly related to pH, transparency, and nitrate concentration. Maximum diameters did not coincide with maximum lengths. A tendency to maintain cell volume throughout the annual cycle was observed, which probably relates to both buoyancy and photosynthetic capacity. These results associate the water ascendancy and the size recovery phases to discharge. Cells become smaller on the ebbing of the flood phase, and the decreasing depth increases the probability that the alga will be disentrained from the turbulent field. The loss during low water would act as a stimulus for auxosporulation, contributing to the production of large cells to start off the next population. Received: August 12, 2000 / Accepted: November 14, 2000     

Observations on Aulacoseira nipponica from Lake Biwa, Japan, and Aulacoseira solida from North America (Bacillariophyceae)

A recent diatom, Aulacoseira nipponica (Skvortzow) Tuji comb. et stat. nov., is described from Lake Biwa, Japan, where they had been identified previously as Aulacoseira solida (Eulenstein) Krammer. These forms are compared with populations of A. solida from North America. The Japanese species differs from the North American specimens in characteristics related to the density of striae and form of the rimoportulae.     

AULACOSEIRA SKVORTZOWII SP. NOV. (BACILLARIOPHYTA), A POORLY UNDERSTOOD DIATOM FROM LAKE BAIKAL,RUSSIA1

Aulacoseira skvortzowii sp. nov. is a diatom taxon present in modern plankton assemblages and sedimentary deposits from Lake Baikal, Russia. It has been previously reported as A. islandica (O. Müll.) Simonsen, A. islandica ssp. helvetica (O. Müll.) Simonsen, a sporangial frustule of A. baicalensis (K. Meyer) Simonsen, and Aulacoseira “spore”. However, its microstructure, ecology, and ability to form true resting spores provide ample criteria to describe this diatom as Aulacoseira skvortzowii sp. nov.     

First record of a spiral form of Aulacoseira,A. ambigua f. japonica (F.Meister) Tuji & D.M.Williams,in South African fresh waters

Water quality and algal populations in the Vaal River Barrage Reservoir have been monitored extensively for many decades, because of its importance as a water source for the most densely populated area in South Africa. Although Aulacoseira granulata (Ehrenberg) Simonsen is frequently found and at it times dominates algal assemblages in the Barrage, Aulacoseira ambigua (F.Meister) Tuji & D.M.Williams has never before been recorded at this locality. During a countrywide proficiency-testing scheme for algae counting, coordinated by Rand Water, spiral-shaped diatom colonies with distinctly curved cells were detected during May 2015. Upon investigation, it was found that the spiral colonies were Aulacoseira ambigua f. japonica, its presence in the fresh waters of South Africa being recorded for the first time. Since their first appearance during May 2015, colonies of Aulacoseira ambigua f. japonica have been constantly present in the surface waters of the Barrage. Their presence at this site can be linked to increasing eutrophication in the Vaal River, because the spiral form is known to prefer eutrophic conditions. Centric diatoms rarely form spiral colonies and there is some confusion in the literature as to the identity of this particular form, therefore in this paper we discuss this taxon, its nomenclature and ecological significance.     

Stimulated rejuvenation of dormant Aulacoseira granulata (Bacillariophyta) by Gloeocystis planctonica (Chlorophyta) in a eutrophic river

The abundance of Aulacoseira granulata (Ehrenburg) Simonsen and Gloeocystis planctonica (West & G.S.West) Lemmermann was assessed during the summers of 2005 and 2010 in the eutrophic Fox River, Wisconsin, USA. In both years, a mid‐summer bloom of G. planctonica was followed by the rapid growth of A. granulata. Laboratory experiments in which A. granulata was grown in cell‐free filtrate of a G. planctonica culture revealed that the growth of A. granulata was stimulated in the G. planctonica‐treated medium relative to controls. This effect was detected when dormant A. granulata cells were used as the source culture for the experiment but not when actively growing cells were used. Dormant A. granulata also grew more rapidly in river water collected after the 2010 G. planctonica bloom relative to river water collected before the bloom. These results suggest that the summer bloom of A. granulata in the river was stimulated by G. planctonica. This relationship can be described as stimulated rejuvenation, an interaction where the transition of an algal resting stage into active growth is triggered by exposure to another species.     

Vertical mixing,size change and resting stage formation of the planktonic diatom Aulacoseira baicalensis

Aulacoseira baicalensis (K. Meyer) Simonsen is a freshwater planktonic diatom that undergoes large seasonal changes in cell morphology related to changes in vertical mixing. Short cells (10–20 µm) with thin walls were formed under the ice of Lake Baikal but cell lengths increased up to 150 µm by the time mixing depth reached over 100 m in June. These long cells became resting stages that were packed with reserve products and had siliceous walls up to 4 µm thick. Increase in mixing depth gave access to sufficient silica for completion of resting stages in most years but not in high biomass years, which has long-term implications for the population. Wall thickening reduced the risk of dissolution during dormancy but it also reduced cell volume. Therefore, by increasing length, cells maintained storage space for reserves. Seasonal changes in valve length showed that individual valves did not last more than 6 months, equivalent to 5 to 10 divisions. Separation valves were important in determining the number of cells per filament during spring growth but cell breakage became more important during summer dormancy. Resting stages survived in cool, intermediate depths (50–150 m) during summer stratification and were returned to the surface during autumn overturn.     

Seasonal succession of phytoplankton in Lake Yogo over 2 years: effect of artificial manipulation

We studied the seasonal variation in concentrations of nutrients and phytoplankton in Lake Yogo for 2 years, from May 2000 to May 2002, in order to clarify the seasonal succession of phytoplankton and the effect of various manipulations on it. It was revealed that in spite of the installation of aeration systems and the pumping of mesotrophic water from Lake Biwa during the summer season, the trophic state of Lake Yogo overall has not improved during the past few decades. However, the pumping of water from Lake Biwa did affect the concentrations of nutrients and the periods of cyanobacterial bloom during the summer. The pumping period was different in each year, and the cyanobacterial bloom occurred during the period without pumping in both years. The aeration destratification was not strong enough to prevent cyanobacterial blooms. Cyanobacteria and Bacillariophyceae contributed most to the phytoplankton biomass in both years. Aphanizomenon, Anabaena, and Microcystis were the main genera among cyanobacteria. The bloom of Aphanizomenon or Anabaena occurred early in the summer, and was then replaced by Microcystis. Aphanizomenon was almost always present, and often formed bloom even in winter. The seasonal succession of Bacillariophyceae was almost the same in both years and was well categorized: winter-growing species such as Aulacoseira pusilla (F. Meister) Tuji et Houki and species of Thalassiosiraceae, spring-growing species such as Asterionella formosa Hassall, Fragilaria crotonensis Kitton, and Synedra cf. acus, and fall-growing species such as Aulacoseira ambigua (Grunow) Simonsen, and Aulacoseira granulata (Ehrenb.) Simonsen.     

Aulacoseira subarctica: taxonomy,physiology, ecology and palaeoecology

Knowledge of the morphology, taxonomy, physiology, ecology and palaeoecology of the filamentous freshwater diatom Aulacoseira subarctica (O. Müller) Haworth is reviewed from the literature. The species is widely distributed across Northern Europe, Scandinavia and North America, Japan, China, Australia and New Zealand, in the last usually as fo. subborealis. The species is rare in the Tropics and positive identifications are lacking for Africa. The importance of correct identification is stressed because literature reports of its occurrence often need revision. A comparison is made between two sites with detailed records of its seasonal cycle. Blelham Tarn, England, is a clear-water seasonally stratified lake; Lough Neagh, Northern Ireland, is a very large turbid and unstratified lake. In spite of their contrasting characters, Aulacoseira subarctica succeeds in both lakes. In Blelham Tarn, there is a strong seasonal cycle of growth, dormancy on the sediment and further growth on re-suspension. In Lough Neagh, there is a large deposition of cells at the end of the spring bloom but few of these cells survive grazing by benthic animals. Fossil occurrences are summarized from the species’ initial appearance in the Pliocene and its later occurrence during the last inter-glacial (Eemian) deposits in NW Europe, where it is an important ecological indicator. Palaeolimnological studies are reviewed to describe the contemporary distribution and ecological preference of this widespread diatom. Aulacoseira subarctica usually appears in response to moderate increases in nutrients but is disadvantaged by further enrichment. In Blelham Tarn the species only became abundant during the twentieth century, reaching a peak between 1930 and 1960. With nutrient enrichment, abundance has declined. In Lough Neagh, it has been present for much of the post-glacial period and still thrives today in spite of the highly enriched state of the lake. The species has disappeared from many eutrophic lakes and its sustained existence in Lough Neagh is anomalous. Lough Neagh may continue to offer a favourable habitat in spite of the poor light climate because the water depth, lack of stratification and long water retention time reduce losses to a sustainable level.