明晰双肋藻(硅藻门)的超微结构研究北大核心CSCD

在对武陵山区硅藻分类和多样性研究中,收集到了一种双肋藻的标本,经研究鉴定,其为明晰双肋藻[Amphipleura pellucida(Kützing)Kützing]。光学显微镜观察和扫描电子显微镜观察结果表明:明晰双肋藻具有以下特征:(1)纺锤形的壳瓣外形。(2)长而直的中央胸骨。(3)仅着生在靠近壳面两端的短壳缝系统。(4)线纹密度为38~39条/10μm,孔纹密度为54~58个/10μm。(5)壳缝的外近缝端呈直线状,远缝端略微膨大。(6)孔纹内侧开口被圆形筛膜覆盖。该研究结果为明晰双肋藻提供了清晰的超微结构图片资料以及科学的描述。     

一种硅藻中国新记录属种——科氏杜氏藻

科氏杜氏藻是一种泥生或附沙生硅藻。该文对最近刚确立的一个硅藻属——杜氏藻属进行了介绍,利用光学和扫描电子显微镜对2019年4月20日采自东洞庭湖国家级自然保护区的科氏杜氏藻标本进行了观察研究。结果表明该标本具有以下主要形态特征:(1)壳面椭圆披针形。(2)中央区为蝴蝶结形,没有延伸至壳缘。(3)线纹在壳面大部分区域呈辐射状排列,在两端近平行排列,中部线纹密度20~22条/10μm。(4)孔纹圆形或近圆形,在内壳面被圆顶状的孔膜覆盖。(5)在壳面两端存在假隔片。该文调查采集的科氏杜氏藻种群的形态特征与模式种群相吻合,该属在中国是首次报道,为中国新记录属。     

双壳缝硅藻中国2新记录种——肿胀类辐节藻和英格兰盘状藻具孤点变种

该研究利用光学和扫描电子显微镜,对采自东洞庭湖国家自然保护区的2种双壳缝硅藻中国新记录种——肿胀类辐节藻和英格兰盘状藻具孤点变种的标本进行了详细形态学研究。观察发现：(1)肿胀类辐节藻具有4个鉴定特征：①壳瓣轮廓在大的标本中呈披针形,在小的标本中呈椭圆披针形;②线纹在壳面中部呈辐射状排列,彼此间隔相对较宽;③假隔片在壳面两端都存在;④ 孔纹在内壳面被具微孔的膜完全覆盖。(2)英格兰盘状藻具孤点变种也具有4个鉴定特征：①壳瓣线性椭圆形或椭圆形;② 线纹除了在壳面两端呈平行排列外,在壳面大部区域呈辐射状排列,中部线纹密度10～14条/10 μm;③在壳面中央有一个孤点;④孔纹内部开口被由4个支柱支撑的孔板所覆盖,孔纹密度35～40个/10 μm。该研究的详细描述和清晰的插图为肿胀类辐节藻和英格兰盘状藻具孤点变种的准确鉴定提供了参考。     

芬兰贝氏藻(硅藻门)的超微结构研究

以采集于青海湖的石附生硅藻(芬兰贝氏藻)为样品,用10%的HCl溶液溶解样品中含钙的固体化合物,再加入30% H₂O₂溶液氧化去掉硅藻细胞的有机物质,获得干净的硅藻标本。利用Naphrax^ 封装剂制成永久装片,在光学和电子显微镜下对其形态特征进行了详细研究。结果表明：(1) 在光学显微镜下芬兰贝氏藻具有披针形的壳瓣外形、尖圆的壳面末端和明显伸长的中轴区三个特征。(2) 在扫描电子显微镜下芬兰贝氏藻紧邻中央区的孔纹明显伸长,其长度为2～4个正常孔纹的长度。(3) 通过文献查阅和相似种类的比较发现,同时具有尖圆的末端和明显伸长的紧邻中央区的孔纹是芬兰贝氏藻鉴定的独特性状组合,故芬兰贝氏藻的身份可由此确定。该研究首次报道了芬兰贝氏藻在中国的分布。     

硅藻中国新记录种——比提基金长篦藻

该研究利用光学和扫描电子显微镜对采自湖南东洞庭湖国家级自然保护区的硅藻标本进行了观察,鉴定出其中一种硅藻为比提基金长篦藻(Neidium beatyi Hamilton et al.)。结果表明,该长篦藻具有以下鉴定特征:(1)线性椭圆至线性披针形的壳瓣外形。(2)壳面两侧具有3～5条纵向线。(3)向相反方向弯曲的两近缝端,呈叉状分枝的远缝端末梢及顶端的三角形硅质顶盖。(4) 16～18条/10μm的线纹密度和14～18个/10μm的孔纹密度。(5)一些孔纹内部开口周围的4～7个豆状突出物。本研究结果与比提基金长篦藻模式种群的形态特征和数量性状均吻合,故确定其为比提基金长篦藻;增加了比提基金长篦藻的新地理分布区域——中国洞庭湖。     

我国硅藻类的新记录属——微舟藻属及其一新种(英文)

利用透射电镜对采自东黄海海域典型站位的微型硅藻(nanodiatom,<20mm)进行了研究。观察到我国微型硅藻类的一个新记录属微舟藻属NanoneisR.E.Norris以及该属的一个新种长微舟藻Nanoneislongtasp.nov.。该属的主要特征是壳面两侧对称,具有不完全壳缝,壳面除中轴区外都有横肋纹或长室孔分布。本文描述该属的两个种,其中海斯微舟藻(NanoneishasleaeR.E.Norris)为我国的新记录种,长微舟藻为新种,两种之间主要的区别特征是壳面外形、长宽比例以及壳面横肋纹的密度。并较详细地描述了该属种类的分类特征、生态习性和分布。     

我国硅藻类的新记录属--微舟藻属及其一新种

利用透射电镜对采自东黄海海域典型站位的微型硅藻(nanodiatom,〈20μm)进行了研究.观察到我国微型硅藻类的一个新记录属:微舟藻属Nanoneis R.E.Norris以及该属的一个新种:长微舟藻Nanoneislongta sp.nov..该属的主要特征是:壳面两侧对称,具有不完全壳缝,壳面除中轴区外都有横肋纹或长室孔分布.本文描述该属的两个种,其中海斯微舟藻(Nanoneis hasleae R.E.Norris)为我国的新记录种,长微舟藻为新种,两种之间主要的区别特征是壳面外形、长宽比例以及壳面横肋纹的密度.并较详细地描述了该属种类的分类特征、生态习性和分布.     

大兴安岭地区硅藻中国新记录

报道了采自中国大兴安岭地区的中心类及无壳缝类硅藻植物5属9种,其中含3个中国新记录种:正链藻属的角状正链藻Orthoseira roeseana(Rabenhorst)O'Meara、脆杆藻属的古拉德脆杆藻Fragilaria goulardii(Brébisson)Lange-Bertalot和菱形脆杆藻Fragilaria nitzschioides Grunow。对国内文献报道较少的正链藻属、假十字形藻属、类十字形藻属、十字形藻属植物的形态特征进行了描述;对9种硅藻植物的分类特征及生态分布特点进行了描述。     

形形色色的藻类植物

图1-2 甲藻门 1.Gymnodinium eucyanochroum扫描电镜照片。示细胞的横沟和纵沟中各有1条鞭毛;2.角甲藻Ceratiumhirundinella背面观,示横沟、1个顶角和3个底角,淡水产。图3金藻门锥囊藻属Dinobryon树状群体,每个细胞外均有1个钟罩状的囊壳。生活于清洁的淡水中。图4-7硅藻门(细胞均经过酸化处理,示壳面花纹) 4.蛇目圆筛藻Coscinodiscus argus壳面圆形,具六角形孔纹,呈放射状和螺旋状排列。海产。     

硅藻中国新记录种——沃氏具脊桥弯藻

本研究利用光学和扫描电子显微镜对采自湖南省江华瑶族自治县一源头水溪流的硅藻标本进行了观察，鉴定出中国新记录一种：沃氏具脊桥弯藻(Oricymba voronkinae Glushchenko, Kulikovskiy & Kociolek)。研究结果显示该具脊桥弯藻具有以下鉴别特征：(1) 壳面呈披针形，末端钝圆；(2) 壳面平坦，壳面和壳套区别明显，被一条边缘脊分开；(3) 边缘脊两侧具凹槽；(4) 近缝端向壳面腹侧偏转，远缝端几乎呈直角向壳面背侧弯曲且在远缝末梢的背侧处有一个缺刻；(5) 壳面中央孤点外侧开口为一个简单圆形，内壳面开口为被向内生长物所遮挡的两个裂缝；(6) 壳面孔纹呈裂缝状，仅近中轴区的孔纹呈半圆至弧形；孔纹的开口被齿状突出物部分遮挡；(7) 顶孔区内侧开口被波浪形的贯壳列硅质条所覆盖但未完全封闭内侧开口；(8) 壳面中部的线纹密度为8～11条/10 μm，孔纹密度25～30个/10 μm。本文提供了沃氏具脊桥弯藻孔纹密度和原始描述中未揭示的顶孔区内壳面的详细超微结构特征。     

OVERLOOKED HETEROPOLARITY IN SURIRELLA CF. FASTUOSA (BACILLARIOPHYTA) AND RELATIONSHIPS BETWEEN VALVE MORPHOGENESIS AND AUXOSPORE DEVELOPMENT

Surirella cf. fastuosa is an apparently isopolar elliptic marine raphid diatom. We observed cells before and after sexual reproduction in monoclonal cultures using light and scanning electron microscopy (LM and SEM). After sexual reproduction cells were approximately twice as large as before, in valve length and width. The stria and infundibula densities were stable during the life cycle. Subtle morphological differences were detectable between the two poles of the frustule. One pole (pole A) was characterized by endings of the external raphe fissure that turned toward the valve face, continuity of the domed wall of the raphe canal externally, an elliptic chamber visible internally, a shallow nick in the interior of the valvocopula. The other pole (pole B) was with the following: straight endings of the external raphe fissures, a dent in the domed wall of the raphe canal externally, a double chamber internally, presence of the open ends of the valvocopula nearby, a deep nick in the valvocopula. Furthermore, at pole A virgae developed at an early stage in morphogenesis, whereas at pole B they were not formed. In the auxospores, pole A was situated beneath the primary transverse perizonial band. Pole A is suggested to be homologous with the head pole in heteropolar Surirella and is the “protopole” likely equivalent to the central nodule in naviculoid taxa. Pole B is homologous with the foot pole in heteropolar Surirella and is the “synaptic pole” formed by fusion of components equivalent to both poles of naviculoid taxa.     

Pleurosigma hinzianum sp. nov. and P. frenguellianum sp. nov. (Pleurosigmataceae,Bacillariophyta) from Argentinean coastal waters,in comparison with P. amara Stidolph and P. elongatum W. Smith

Two new marine diatom species from Argentinean coastal waters, Pleurosigma hinzianum Sterrenburg, Sunesen & Sar, sp. nov. and P. frenguellianum Sunesen, Sterrenburg & Sar, sp. nov., are described. The characters permitting their identification are specified, based on comparison with type material of the morphologically similar species P. amara Stidolph and P. elongatum W. Smith in the light (LM) and scanning electron microscope (SEM). New information on the type material of P. elongatum is presented and its taxonomic concept is emended. The main criteria for separation of the species discussed here are: valve outline, path of the raphe-sternum, raphe angle and angle of intersection of the oblique striae in LM; and external central and terminal raphe fissures, internal details of the central area, external and internal apical structure, and morphology of the hymen-occluded internal pores in SEM. The occurrence of these (and probably other) species in the genus Pleurosigma in net samples is adventitious and not indicative of a true planktonic mode of life.     

ACHNANTHIDIUM DOLOMITICUM SP. NOV. (BACILLARIOPHYTA) FROM OLIGOTROPHIC MOUNTAIN SPRINGS AND LAKES FED BY DOLOMITE AQUIFERS1

A new benthic freshwater diatom, Achnanthidium dolomiticum sp. nov., was identified from light and scanning electron micrographs. The most characteristic morphological features are a narrow, but distinctive fascia; a filiform raphe with narrowly spaced central ends and a very narrow and straight axial area on the raphe valve; a convex‐shaped rapheless valve; the length/width ratio; and valve outline. The new species, has been found so far to be mainly epiphytic on bryophytes and aquatic vascular plants in carbonate springs and lakes of the Italian Alps. The environmental preferences of the new species, as assessed by the comparative analysis of these sites, appear to be quite distinctive. These freshwater habitats are fed by drainage basins dominated by dolomite lithology with medium mineralization, are oligotrophic, and are affected by seasonal desiccation.     

VARIATION IN PATTERNS OF VALVE MORPHOGENESIS BETWEEN REPRESENTATIVES OF SIX BIRAPHID DIATOM GENERA (BACILLARIOPHYCEAE)

Scanning electron microscopic studies of silica valve formation in naviculoid diatoms representing six different genera revealed that the precise sequence of depositional events varied among genera. Valve deposition begins with the formation of the raphe sternum, from which virgae (lateral outgrowths) extend. Areolae (pores) are formed between the virgae by the fusion of cross-extensions (vimines). In most of the species studied ( Craticula ambigua (Kützing) D. G. Mann, Frustulia vulgaris (Thwaites) De Toni, Craspedostauros australis E. J. Cox, and Gomphonema truncatum Ehrenberg), areola (pore) formation began near the raphe sternum before completion of the valve margin, but in Pinnularia gibba Ehrenberg the valve margin fused before the areolae were formed. Silica deposition in all these taxa was mainly distal to proximal (with respect to the cytoplasm), but in Haslea sp. it was mainly proximal to distal. Haslea also differed in that areolae were defined as the valve margin was completed. These data have also contributed to the interpretation of taxonomically important features, such as raphe endings. In P. gibba the internal central raphe fissures were laterally deflected but subsequently obscured by additional silicification of the valve, whereas in G. truncatum they were initially straight, becoming laterally deflected as valves mature. External raphe fissures in Frustulia became Y-shaped only just before maturity; in immature valves they were dotlike, as in Amphipleura Kützing. The comparison of developmental pathways in diatoms is a useful adjunct to morphological and other approaches in diatom systematics and warrants renewed attention.     

Xenococconeis opunohusiensis gen. et sp. nov. and Xenococconeis neocaledonica comb. nov. (Bacillariophyta) from the tropical South Pacific

During a survey of the coral reef diatoms of Moorea Island (Society Archipelago, South Pacific) a small‐sized member of the order Achnanthales was studied using a light microscope (LM) and a scanning electron microscope (SEM). This marine taxon has: a raphe valve (RV) with a non‐crenulate edge; a high cingulum; a sternum valve (SV) often irregularly striated and areolae with concave hymenate pore occlusion; a thick and plain SV valvocopula (SVVC), ring‐shaped, composed of large fused fimbriae, with a central elliptic foramen bordered by the peg‐like edge of the fimbriae. On abvalvar side, the SVVC bears radiate concave and robust transapical ribs, interlinking with short elevated transverse ribs of the RV valvocopula (RVVC). Large marginal fenestrae of the RVVC give access to pseudoloculi. One oblong, unique and striated papilla is located on each RVVC rib. Given this unique set of features, we describe Xenococconeis opunohusiensis gen. et sp. nov. as a new taxon belonging to the Achnanthales. The characteristics of the new taxon are compared with Campyloneis Grunow and Cocconeis Ehrenberg. From New Caledonia, Cocconeis neocaledonica Maillard ex Lange‐Bertalot et Steindorf, a freshwater diatom, was described with two internal septa with marginal pseudoloculi. Based on subsequent SEM illustrations and remarks, we propose the transfer of C. neocaledonica to the new genus, and compare it to the type species, Xenococconeis opunohusiensis.     

A new species of Achnanthes (Bacillariophyceae) from a freshwater habitat in a karst landform from south‐central China

Achnanthes maolanensis nov. sp. is a large diatom collected from subaerial, freshwater habitats in karst landforms in central‐south China. Living cells have two chloroplasts. Valves of this new species are panduriform in outline, slightly constricted in the middle part of the margins, with uniseriate areolae; the raphe is filiform, and there is a linear, thickened stauros in the central area of the RV. On the ARV, there is no central area, and as well there are no terminal orbiculi, marginal ridge, or terminal spine externally. The axial area (rapheless sternum) is located down the center, not offset from the center as in many other species of the genus and is narrow and almost straight. This suite of characters makes the new species easy to distinguish from other species in the genus. Its presence adds further documentation of the unique and diverse freshwater diatom flora from karst habitats in this region of China.     

PYRENOIDS,RAPHES, AND OTHER FINE STRUCTURE IN DIATOMS

Pyrenoids of 6 diatoms, Acnanthes minutissima, Cyclotella meneghiniania, Cymbella affinis, Gomphonema parvulum, Nitzschia sp., and Surirella ovalis, were examined comparatively with the electron microscope. All except those of G. parvulum were membrane-limited. The pyrenoid membrane forms a ridge around the pyrenoid of S. ovalis, C. meneghiniania, and Nitzschia sp. Distended double-disc bands cross the pyrenoids of C. affinis, G. parvulum, S. ovalis, and A. minutissima; single-disc bands occur in C. meneghiniania, and 3 disc bands in Nitzschia sp. The raphe fissures of A. minutissima, Nitzschia sp., and S. ovalis did not contain any cytoplasm or obvious organs of locomotion. In G. parvulum, membranous profiles extend outward from the raphe fissure, but these probably are not responsible for movement. In this diatom 2 membranes usually cross the raphe, and the distance between them fluctuates indicating that they may undulate to force water through the raphe. A 7–10 mμ subfrustular zone is associated with the inner surface of the silica, but separate from the cytoplasmic membrane, in Nitzschia sp. and G. parvulum. In the latter, it is attached to siliceous knobs protruding from the inner surface of the silica. It may join the 2 halves of the frustale, which are otherwise not connected either to each other or to the cytoplasm. Pores 80–100 mμ in diameter occur in the nuclear envelopes of all diatoms examined. Dictyosomes are always perinuclear. In S. ovalis the vesicular complex is a convoluted, single-membrane-limited structure containing a variety of vesicular profiles, and occupying much of the central cytoplasm. Internally it resembles leucosin bodies of a chrysophyte, but the arrangement and morphology of the internal vesicles suggests that intracellular pinocytosis may occur.     

Morphology of the marine epiphytic diatom Cocconeis heteroidea (Bacillariophyceae)

The morphology and fine valve structure of the marine epiphytic diatom Cocconeis heteroidea Hantzsch have been investigated. The entire frustule, including the internal and external structure of the raphid valve (RV) and araphid valve (AV), and the complete cingulum, are described using light microscopy and scanning and transmission electron microscopy, using a bleaching method. The strongly sigmoid raphe terminates in elongate hooked helictoglossae internally. The hymenes, with perforations arranged in a centric array, are located near the internal openings of the areolae in the RV. The striae in the AV consist of alveoli occluded by hymenes, that have perforations arranged in a parallel array and are located near the outer surface. The complete cingulum of AV consists of three open bands without fimbriae: a valvocopula, a copula with a ligula and a pleura with a small ligula. The RV has only a valvocopula which is open type and not fimbriate.     

A new marine diatom, Cocconeis shikinensis sp. nov. (Bacillariophyceae) from Japan

A new species of Cocconeis has been found growing on the green seaweed Caulerpa racemosa (Forsskål) J. Agardh var. laete‐virens (Montagne) Weber van Bosse from Shikine Island in the Izu Islands on the Pacific coast of Japan; we propose the name Cocconeis shiki‐nensis Hid. Suzuki and describe the species by light microscopy (LM) and electron microscopy (EM). This taxon was also collected from the plastic plates used for rearing in seed production systems of the abalone Nordotis discus hannai Ino and the horned turban Turbo cornutus Solander in the Toyama Prefectural Fisheries Research Institute facing the Sea of Japan. The main morphological features of C. shikinensis are as follows. The valves are elliptic. The valve face of the raphid valve (RV) is slightly concave and that of the araphid valve (AV) is complementary to the RV and convex. The single plastid is flat, C‐shaped and elaborately lobed. The raphe on the RV is straight. The each terminal area expands to both sides along the valve margin, forming an arrowhead‐shaped, thickened hyaline area. The striae consist of small, round areolae and are radiate and uniseriate. On the AV, the striae consist of several alveoli. Each alveolus opens internally by means of a circular foramen. The valvocopula of each valve is fimbriate and open. The cingulum attached to the AV consists of three girdle bands; a valvocopula and two bands (copula and pleura), which are open and have ligulae. The relationship between C. shikinensis and similar members of the genus Cocconeis is discussed.     

THE “PARADOX” DIATOM BACILLARIA PAXILLIFER (BACILLARIOPHYTA) REVISITED1

Defined by its unique colonial locomotion, Bacillaria paxillifer (O. F. Müll.) Hendey was recognized as a single, pandemic species by many phycologists. However, reinvestigation of colonies from different habitats revealed three distinct groups: (A) brackish/freshwater, (B) marine littoral, and (C) marine planktonic taxa. Groups differed in colony and cell form, raphe flanges (RFs), shape and position of transapical ribs (Tr's), and morphogenesis. Linear‐shaped species were restricted to group A: Tr's thickened principally to the interior. Lanceolate forms were confined to groups B and C: valve formation proceeded from an internal base layer to the exterior. The planktonic species differed in the shape of its raphe slit, and the transformation of girdle bands (GBs) into “winglets.” Taxa also differed in chloroplast shape and number. All species formed motile colonies. Siblings adhered via elastic fibrils secreted through their raphe. Raphe ribs were held in position by siliceous clamps (fibulae), anchored in an extra pair of axial ribs (fibular ribs) parallel to the raphe ribs. This raphe system resembled that of Cylindrotheca rather than the “canal raphe” of Nitzschia. Many valves were asymmetric along the apical axis due to protruding RFs shuttling in a 1:1 ratio within a colony, but raphe slits were mirror images, as were the growth direction of fibulae and position of plastids, with pyrenoids tilted in the same direction. Species possessed four open GBs per epitheca; the third band invariably bore an internal, organic ridge to aid in adhesion of the plasmalemma during cleavage. The results suggested that these taxa are a natural phylogenetic group, requiring precise determination of their taxonomic position.