CYTOCHALASIN B INFLUENCES DICTYOSOMAL VESICLE PRODUCTION AND MORPHOGENESIS IN THE DESMID EUASTRUM1

Cytochalasin B (CB) applied to young developing cells of the desmid Euastrum oblongum Ralfs ex Ralfs, at concentrations that do not entirely inhibit cytoplasmic streaming, retarded cell growth and caused malformations of cell shape. While the basic symmetry of the cell was maintained, only the first indentations were formed and the cell body appeared to be swollen. Electron microscopic investigations revealed that vesicle production at the dictyosomes was disturbed by cytochalasin. In contrast to untreated control cells, where vesicles with electron-dense contents (“dark vesicles”) were formed during primary wall formation, vesicles pinched off by the dictyosomes during CB treatment exhibited an “empty” appearance. These vesicles, which correspond to the “dark vesicles” in size, were accumulated around the dictyosomes without being transported to the plasma membrane and were frequently connected to the trans-cisternae of the Golgi bodies. We speculate that CB may influence the transfer of products from the endoplasmic reticulum (ER) to the dictyosomes via transition vesicles, which results in a disturbed vesicle production at the Golgi bodies. CB also causes a shift in ER and dictyosome distribution. Moreover, a cortical actin system appears to be involved in the cell shaping of Euastrum. The arrangement of microtubules around the nucleus is not affected by the drug.     

Desmids from Pachmarhi,Madhya Pradesh,India

An illustrated account is given of 68 desmids from streams running below Pachmarhi plateau in Madhya Pradesh, India, Two varieties of Euastrum are new to science.     

喀纳斯自然保护区鼓藻类新疆新记录植物

2013年8月,在新疆喀纳斯自然保护区湿地进行鼓藻类植物调查,并对采集到的50余号藻类标本进行鉴定,结果发现,有8个分类单位为鼓藻类植物新疆新记录,隶属于4属,包括5种2变种1变型:喙状新月藻(Closterium rostratum Ehrenberg)、宽带鼓藻厚变种(Pleurotaenium trabecula var.crassum Wittrock)、不定凹顶鼓藻(Euastrum dubium Ngeli)、近胡瓜鼓藻(Cosmarium subcucumis Schmidle)、近颗粒鼓藻[Cosmarium subgranatum(Nordstedt)Lütkemüller]、凹缘鼓藻(Cosmarium tatricum Raciborski)、特平鼓藻拔萃变种变型(Cosmarium turpinii var.eximium W.et G.S.West f.Jao)和波缘鼓藻阿拉斯加变种(Cosmarium undulatum var.alaskanum Croasdale)。对其分类学特征进行了详细描述,给出了它们的生境特征。这些新记录的发现,为新疆的藻类植物资源提供了基础资料。     

New and interesting desmids (Zygnematales, Chlorophyceae) collected from Brazil and Argentina

The morphology and taxonomy of nine desmid taxa belonging to the three genera Closterium, Euastrum and Cosmarium are studied based on freshwater algal collections from Brazil and Argentina. They represent five new varieties (Closterium cynthia De Notaris var. minutum Kanetsuna var. nov., Euastrum attenuatum Wolle var. saitoi Kanetsuna var. nov., Cosmarium laticollum Delponte var. minutum Kanetsuna var. nov., Cosmarium pseudovariolatum Grönblad var. major Kanetsuna var. nov. and Cosmarium taxichondrum Lundell var. yamagishii Kanetsuna var. nov.), two new forms (Euastrum hypochondrum Nordstedt var. hypochondrum f. divergens Kanetsuna f. nov. and Euastrum insulare (Wittrock) Roy var. silesiacum (Gronblad) Krieger f. brasiliense Kanetsuna f. nov.) and one new status (Cosmarium pseudovariolatum Gronblad var. incrassatum (Scott et Gronblad) Kanetsuna f. elonga‐tum (Scott et Gronblad) Kanetsuna stat. nov.). In addition, a new combination (Cosmarium pseudovariolatum Gronblad var. incrassatum (Scott et Gronblad) Kanetsuna comb, nov.) is proposed.     

Notes on the variation,geographical distribution and ecology ofEuastrum insulare var.basichondrum (Chlorophyta,Desmidiaceae)

Euastrum insulare var.basichondrum, morphologically taking an intermediate position in respect ofCosmarium trilobulatum var.basichondrum andEuastrum bipapillatum, appeared to exhibit such a wide range of variation that it may be considered identical to the other two above-mentioned taxa. This taxon, after having been studied with both light- and scanning electron microscopy, is re-diagnosed. This alga occurs in wet moss cushions in weakly acid to neutral environments. The relation between such a terraqueous habitat and the principally arctic-alpine distribution and a conceivably associated process of speciation is discussed.     

Some New Taxa of Desmidiaceae from the Hengduan Mountains Region of China

Fifteen new taxa of the Desmidiaceae are described and illustrated from the Hengduan Mountains region of China. They are Euastrum gemmatum f. denticulatum, Cosmarium asphaerosporum var. subcapitum, C. dovrense var. fontanum, C. foveolatum, C. sichuanense, C. subdanicum var. granulatum, C. subsuperbum, C. tibeticum var. papilliferum, C. venustum var. arcuatum, C. yunnanense, Staurastrum elaticeps var. eximium, S. longiradiatum f. basispinulosum, S. pseudosebaldi var. compactum f.reductum, S. sebaldi var. ornatum f. spiniferum,S. sonthalium f. spiniferum.     

大兴安岭阿尔山沼泽鼓藻类中国新记录

大兴安岭阿尔山是我国沼泽分布最集中的地区之一,其中鼓藻类植物十分丰富。2004年7月,2005年8月、10月和2006年5月,作者先后4次在该地区采集标本共260号,在对标本鉴定过程中,发现有中国新记录鼓藻10个分类单位,隶属于4个属,包括8种2变种:厚皮鼓藻加厚变种Cosmarium pachydermumvar.incrassatum、穿孔鼓藻C.perforatum、伸长鼓藻C.protractum、具齿角星鼓藻Staurastrum denticulatum、不等角星鼓藻S.dispar、分叉角星鼓藻具螺纹变种S.furcigerumvar.armigera、近阿维角星鼓藻S.subavicula、近十字角星鼓藻S.subcruciatum、超凡叉星鼓藻Staurodesmus insignis和孟它凹顶鼓藻Euastrum montanum。     

MICROTUBULE-MICROFILAMENT-CONTROLLED NUCLEAR MIGRATION IN THE DESMID EUASTRUM OBLONGUM1

Postmitotic nuclear migration in Euastrum oblongnum Ralfs ex Ralfs starts about 80 min after septum formation with the nucleus leaving its central position in the isthmus and moving into the growing semicell. Nuclear migration is influenced by the chloroplast, which expands into the growing half-cell and pushes the nucleus toward one side of the cell. The nucleus occupies its farthest position from the isthmus when located in the middle of the growing semicell directly under the central depression of the cell surface. It remains in this position during the subsequent stages of cell development and moves back toward the isthmus within a chloroplast groove about 12 h after completion of cell shape formation. Bundles of microtubules (MTs) emanating from a microtubule center surround the nucleus during its motion. They reach far into the growing half-cell as long as the nucleus is moving but vanish when the nucleus stays in the growing semicell. MT-disrupting agents inhibit the backward movement of the nucleus toward the isthmus indicating that MTs are involved in this motion too. Because both MT inhibitors and cytochalasin B influence nuclear motion in Euastrum, an interaction of MTs and microfilaments is thought to function as the motive force for nuclear migration.     

New and interesting desmids (Zygnematales, Chlorophyceae) collected from Asia

Many desmid taxa were found in collections from Asia (Japan, Cambodia, Malaysia and Thailand). The following 21 new taxa and two new combinations belonging to five genera (Closterium, Euastrum, Cosmarium, Xanthidium and Staurastrum) and a rare species of Xanthidium, are reported. These include Closterium nasutum Nordstedt var. kazukoae Kanetsuna var. nov., Closterium nematodes Joshua var. nematodes f. kriegeri Kanetsuna f. nov., Euastrum binale (Turpin) Ehrenberg ex Ralfs var. protuberans Kanetsuna var. nov., Euastrum borgeanum Scott et Prescott var. cambodiense Kanetsuna var. nov., Euastrum dubium Nägeli var. protuberans Kanetsuna var. nov., Euastrum fissum W. et G. S. West var. yasukoae Kanetsuna var. nov., Euastrum gemmatum Brébisson var. tenuius Krieger f. porosum (Förster) Kanetsuna comb. nov., Euastrum pseudojenneri Scott et Prescott var. glabrum Kanetsuna var. nov., Cosmarium denticulatum Borge var. multispinum (Hirano) Kanetsuna comb. nov., Cosmarium furcatospermum W. et G. S. West var. fallax Kanetsuna var. nov., Cosmarium pileatum Borge var. cambodiense Kanetsuna var. nov., Cosmarium retusiforme (Wille) Gutwinski var. incrassatum Gutwinski f. retusum Kanetsuna f. nov., Cosmarium trapezoideum Kanetsuna sp. nov., Cosmarium zonatum Lundell var. zonatum f. majus Kanetsuna f. nov., Xanthidium cristatum Brébisson var. delpontei Roy et Bisset f. mizoroensis Kanetsuna f. nov., Xanthidium fasciculatum Ehrenberg ex Ralfs var. siamense Kanetsuna var. nov., Xanthidium pseudofreemanii Kanetsuna sp. nov., Xanthidium subtrilobum W. et G. S. West var. inornatum Skuja f. depressum Kanetsuna f. nov., Xanthidium subtrilobum W. et G. S. West var. inornatum Skuja f. singulare Kanetsuna f. nov., Staurastrum boergesenii Raciborski var. verrucosum Kanetsuna var. nov., Staurastrum dickiei Ralfs var. polypyrenoideum Kanetsuna var. nov., Staurastrum neglectum G. S. West var. fuseense Kanetsuna var. nov., Staurastrum trissacanthum Scott et Prescott var. dissacanthum Scott et Prescott f. longispinum Kanetsuna f. nov., and a rare interesting form, Xanthidium superbum Elfving var. centricornis Prowse.