囊裸藻属与陀螺藻属囊壳微细结构及元素组成比较

对采自自然水体中囊裸藻属(Trachelomonas)的8种和陀螺藻属(Strombomonas)的两种藻类的囊壳微细结构和元素组成进行了比较分析,并探讨了这两个属的系统演化关系。结果表明：组成囊壳的矿质元素主要是铁和硅,在陀螺藻和表面粗糙的囊裸藻中,硅的含量较高,铁的含量相对较低;在大多数囊裸藻中,尤其是表面致密、光滑的种类中,铁的含量较高,硅的含量较低,矿质元素的组成与囊壳的颜色无直接关系。建议将陀螺藻属(Strombomonas)撤消,原陀螺藻属的种作为囊裸藻属(Trachelomonas)中的一个种组(Group),它们是裸藻科中最原始的具囊壳的类群。     

念珠藻属植物hetR基因的适应性进化分析

以念珠藻属(Nostoc)及其近缘类群hetR基因的51条序列为研究对象,对hetR基因的编码蛋白进行生物信息学分析和系统发育分析,并使用分支模型、位点模型和分支-位点模型进行该基因位点的适应性进化研究。系统发育分析结果显示,51条hetR基因蛋白序列可分为4个大分支。适应性进化分析结果表明,在3种进化模型中,大多数分支及藻株都没有检测到统计学上具有显著性的正选择位点,说明检测的位点大多处于负选择压力下。但在普通念珠藻(Nostoc commune,CHAB2802)中检测到正选择位点(126T),提示念珠藻属植物hetR基因发生了适应性改变。     

囊裸藻属与陀螺藻属囊壳微细结构及元素组成比较

对采自自然水体中囊裸藻属(Trachelomonas)的8种和陀螺藻属(Strombomonas)的两种藻类的囊壳微细结构和元素组成进行了比较分析,并探讨了这两个属的系统演化关系.结果表明:组成囊壳的矿质元素主要是铁和硅,在陀螺藻和表面粗糙的囊裸藻中,硅的含量较高,铁的含量相对较低;在大多数囊裸藻中,尤其是表面致密、光滑的种类中,铁的含量较高,硅的含量较低,矿质元素的组成与囊壳的颜色无直接关系.建议将陀螺藻属(Strombomonas)撤消,原陀螺藻属的种作为囊裸藻属(Trachelomonas)中的一个种组(Group),它们是裸藻科中最原始的具囊壳的类群.     

基于叶绿体16S rRNA的绿色裸藻类系统发育及性状进化研究

该研究基于叶绿体16S rRNA基因序列,构建绿色裸藻类的系统发育树,并对绿色裸藻类植物8个形态性状进行祖先重建分析,以明确绿色裸藻类植物的系统演化关系,为研究该类植物的起源提供理论依据。结果表明：(1)贝叶斯法构建的绿色裸藻类系统发育树显示,双鞭藻属与拟双鞭藻属互为姐妹群,扁裸藻属、鳞孔藻属和盘裸藻属亲缘关系较近,而囊裸藻属和陀螺藻属亲缘关系较近,裸藻属、隐裸藻属、柄裸藻属和旋形藻属亲缘关系较近,表明裸藻属不是一个单系类群。(2)基于形态性状的祖先重建结果显示,绿色裸藻类相对原始的7个性状包括：表质柔软易变形,出现螺旋形线纹,细胞后端渐尖或尖尾刺状,无囊壳,叶绿体为片状、盾状或大盘状,具无鞘蛋白核,副淀粉粒为小颗粒状且数量不定,而鞭毛长度不能推断可能的祖先状态。(3)综合8种性状祖先重建结果发现,裸藻属和眼裸藻属植物具有所有原始性状,可能是最先出现的绿色裸藻类的祖先。     

鄂西地区发现的我国裸藻门新记录

1981年5—6月,作者在鄂西一带,对各种生态环境中的藻类进行了一次采集。随后,又对采得的浮游藻类中的裸藻门植物进行鉴定和研究,发现了不少在我国尚未报道过的种类。有些还是较为罕见的种类。它们分别隶属于裸藻属(Euglena)的有8种(包括变种,下同),扁裸藻属(Phacus)的有5种,囊裸藻属(Trachelomonas)的有1种,陀螺藻属(Strombomonas)的有2种,柄裸藻属(Colacium)的有1种,变     

湖北省楔桥弯藻属新种类

楔桥弯藻属(Gomphocymbella)是由Mueller在1905年建立的,它兼有桥弯藻属和异极藻属的双重特性。虽然对它的系统发育及分类问题仍在讨论之中,但一般把它归于异极藻科中。它较为罕见,至今报道的种类仅有10个左右。在我国至今只报道有一个种。近几年来,对湖北省硅藻类中的异极藻科(Gomphomenaceae)进行了分类学研究,发现有3个楔桥弯藻属的种类,其中2个为新种类：疏纹楔桥弯藻(Gomphocymbella laxistria Shi et N.Li）和不对称楔桥弯藻(G．asymmetrica Shi et N.Li);另一个种为我国首次报道的新记录：波润楔桥弯藻(G．brunii(Fricke)O．Mailer)。     

淡水刚毛藻目一新组合种及其系统发育分析

作者于2012-2014年先后在湖北省采集到4株刚毛藻目的丝状绿藻。经鉴定,其形态特征和莫拉瓦刚毛藻Cladophora moravica Gardavsk(1986)非常相似;但相较于刚毛藻属各个种的形态,4株藻体更接近黑孢藻科的分类特征。基于SSU和LSU rDNA序列构建的系统发育树显示,4株刚毛藻目的丝状绿藻均属于黑孢藻科拟湖球藻属(Aegagropilopsis)。据此,作者建议将该种名称作为一个新组合处理,即莫拉瓦拟湖球藻Aegagropilopsis moravica(Dvoˇrák)Zhao et Liu com.nov。拟湖球藻属仅含有3个种:莫拉瓦拟湖球藻、硬枝拟湖球藻和棒状拟湖球藻,其形态特征与湖球藻相近且易混淆,故采用核基因组序列分析方法区分二者是非常有效的。     

中国具囊壳裸藻类的新种类

本文报道了在我国首次发现的１３个具囊壳裸藻类的新种类,在它们之中隶属于囊裸藻属的有５个新变种;属于陀螺藻属的有８个新变种。     

裸蒴属的核型及三白草科四属间系统关系的探讨

本文首次报道三白草科裸蒴属中华裸蒴(Gymnotheca chinensis Decne)和白苞裸蒴(G. involucrata Pei)的染色体数目。两个种的体细胞染色体数均为2n=18,染色体基数为x=9。三白草科原始祖先的染色体基数假定为x=11,裸蒴属可能是经非整倍减少演变而来。裸蒴属间期核型属球状或棒状前染色体型。本文根据三白草科染色体研究的结果和现代地理分布格局,结合其他分枝学科的研究资料,对科下四属间的系统发育关系提出了初步假设。     

链形藻类的中国新记录属—中眼藻属

中眼藻属(Mesostigma)被认为是与高等植物亲缘关系最近的单细胞鞭毛藻类, 是研究高等植物起源的关键类群之一。已有研究表明中眼藻主要分布于静止的淡水水体中, 诸如池塘、水库和小型湖泊等, 然而中国至今仍未有该藻的报道。本研究在重庆合川和福建九龙江采集到2株单细胞鞭毛藻类, 对其进行形态观察并基于18S rDNA序列进行了系统发育分析。研究结果表明这2株藻为中眼藻属的绿色中眼藻(Mesostigma viride)。此外, 研究从三峡库区的环境DNA中也鉴定出中眼藻的存在, 且主要出现在秋季, 说明秋季可能是在中国内陆采集中眼藻的最佳季节。研究是中眼藻属在中国的首次报道, 为今后的中眼藻相关研究奠定了基础。     

A new photosynthetic euglenoid isolated in Poland: Euglenaria clepsydroides sp. nov. (Euglenea)

In this paper, we describe a new photosynthetic euglenoid species, Euglenaria clepsydroides Zakry?, sp. nov., found in Poland. A large population of this species exists in a few, small, eutrophic bodies of water inside the Masurian Landscape Park (covering a part of the Masurian Lake District in Poland). The characteristic and atypical (hourglass-like) cell shape sets it well apart from the other species that have been described up to now. This atypical cell shape has so far been observed only in three species – Lepocinclis constricta, Euglena undulata and Euglena gymnodinioides – whose other morphological characteristics, such as the number and morphology of chloroplasts, the lack of mucocysts, and nuclear SSU rDNA sequence data, exclude the possibility that they could be close relatives of Euglenaria clepsydroides. On the phylogenetic tree, the new species is situated within the Euglenaria clade. While it is a sister group of the clade that includes representatives of Euglenaria anabaena, the two species are clearly morphologically distinct.     

151 Phylogenetic Analysis of The Subgenus Euglena with Particualr Reference to the Type Species Euglena Viridis (Euglenophyceae)

Euglena viridis was first described by Antony van Leeuwenhoek in 1674. This taxon later became the type for the genus Euglena erected by Ehrenberg in 1838. The primary characters that distinguish this taxon are the single stellate chloroplast and spherical mucocysts. A number of related Euglena species are similar in size, bear one or two stellate plastids and possess spherical or spindle-shaped mucocysts. We conducted morphological and molecular studies on taxa in the subgenus Euglena (all of which bear stellate chloroplasts) and compared this to genera in the subgenus Calliglena (non-stellate chloroplasts). Morphologically the strains in subgenus Euglena were very similar, except for chloroplast number and mucocyst shape. The E. stellata group has one chloroplast and a distinctive spindle-shaped mucocyst; the E. geniculata group has two chloroplasts and spherical mucocysts; the E. viridis group has one chloroplast and spherical mucocysts. Molecular analyses using SSU and LSU rDNA demonstrated that the subgenus Euglena is not monophyletic. The combined SSU/LSU trees provide strong support for a stellate clade (subgenus Euglena ), but one strain of E. viridis diverges at the base of the Euglena/Calliglena lineage. Multiple subclades are found within the main stellate clade. E. tristellata forms a separate divergence and four E. stellata strains form a single, well-supported subclade. Two E. viridis strains are among the E. geniculata group clade, while six others form two separate, but well-supported clades. This study demonstrates that the type species, E. viridis , is paraphyletic and will need to be redefined.     

The chloroplast genome of Phacus orbicularis (Euglenophyceae): an initial datum point for the phacaceae

The Euglenophyceae chloroplast was acquired when a heterotrophic euglenoid engulfed a green alga and subsequently retained the algal chloroplast, in a process known as secondary endosymbiosis. Since this event, Euglenophyceae have diverged widely and their chloroplast genomes (cpGenomes) have as well. Changes to the cpGenome include extensive gene rearrangement and the proliferation of introns, the analyses of which have proven to be useful in examining cpGenome changes throughout the Euglenophyceae. The Euglenales fall into two families, Euglenaceae and Phacaceae. Euglenaceae contains eight genera and at least one cpGenome has been published for each genus. Phacaceae, on the other hand, contains three genera, none of which have had a representative chloroplast genome sequenced. Members of this family have many small disk‐shaped chloroplasts that lack pyrenoids. We sequenced and annotated the cpGenome of Phacus orbicularis in order to fill in the large gap in our understanding of Euglenophyceae cpGenome evolution, especially in regard to intron number and gene order. We compared this cpGenome to those of species from both the Euglenaceae and Eutreptiales of the Euglenophyceae phylogenetic tree. The cpGenome showed characteristics that were more derived than that of the basal species Eutreptia viridis, with extensive gene rearrangements and nearly three times as many introns. In contrast, it contained fewer introns than all but one of the previously reported Euglenaceae cpGenomes, had a smaller estimated genome size, and shared greater synteny with two main branches of that family.     

Chloroplast Genome Evolution in the Euglenaceae

Over the last few years multiple studies have been published outlining chloroplast genomes that represent many of the photosynthetic euglenid genera. However, these genomes were scattered throughout the euglenophyceaean phylogenetic tree, and focused on comparisons with Euglena gracilis. Here, we present a study exclusively on taxa within the Euglenaceae. Six new chloroplast genomes were characterized, those of Cryptoglena skujai, E. gracilis var. bacillaris, Euglena viridis, Euglenaria anabaena, Monomorphina parapyrum, and Trachelomonas volvocina, and added to six previously published chloroplast genomes to determine if trends existed within the family. With this study: at least one genome has now been characterized for each genus, the genomes of different strains from two taxa were characterized to explore intraspecific variability, and a second taxon has been characterized for the genus Monomorphina to examine intrageneric variability. Overall results showed a large amount of variability among the genomes, though a few trends could be identified both within Euglenaceae and within Euglenophyta. In addition, the intraspecific analysis indicated that the similarity of a genome sequence between strains was taxon dependent, and the intrageneric analysis indicated that the majority of the evolutionary changes within the Euglenaceae occurred intergenerically.     

PHYLOGENETIC ANALYSIS OF THE GENUS EUGLENA (EUGLENOPHYCEAE) WITH PARTICULAR REFERENCE TO THE TYPE SPECIES EUGLENA VIRIDIS1

Euglena viridis (subgenus Euglena) serves as the type species for the genus Euglena. In this study, molecular phylogenetic analyses using a small subunit (SSU) and a combined SSU–partial large subunit rDNA data set for members of the genus Euglena showed that strains identified as E. viridis on the basis of morphology are distributed between two separate nonsister clades. Although all the E. viridis strains examined were morphologically indistinguishable and possessed spherical mucocysts and stellate chloroplasts with one paramylon center, there was a high degree of sequence divergence between the E. viridis strains in different clades, making this a cryptic species. Like E. viridis, all taxa from the subgenus Euglena are characterized by having one or more stellate chloroplasts with paramylon grains clustered around the center of the chloroplast. These additional taxa were divided into four clades in all the molecular analyses. Strains of Euglena stellata formed two nonsister clades whose members had a single aggregate chloroplast with paramylon center and spindle‐shaped mucocysts. A geniculata clade included species with one or two stellate chloroplasts with paramylon centers and spherical mucocysts, and the cantabrica clade had members with one stellate chloroplast with paramylon center and spherical mucocysts often arranged in spiral rows. Interspersed among these were three additional clades bearing taxa from the subgenus Calliglena that contains members with discoid plastids and pyrenoids that may or may not be capped with paramylon. These taxa formed a laciniata clade, mutabilis clade, and gracilis clade. This study demonstrates that E. viridis and E. stellata are cryptic species that can only be distinguished at the molecular level. Because E. viridis is the designated type species for the genus Euglena, we designated an epitype for E. viridis.     

Evolution of the Chloroplast Genome in Photosynthetic Euglenoids: A Comparison of Eutreptia viridis and Euglena gracilis (Euglenophyta)

The chloroplast genome of Eutreptia viridis Perty, a basal taxon in the photosynthetic euglenoid lineage, was sequenced and compared with that of Euglena gracilis Ehrenberg, a crown species. Several common gene clusters were identified and gene order, conservation, and sequence similarity was assessed through comparisons with Euglena gracilis. Significant gene rearrangements were present between Eutreptia viridis and Euglena gracilis chloroplast genomes. In addition, major expansion has occurred in the Euglena gracilis chloroplast accounting for its larger size. However, the key chloroplast genes are present and differ only in the absence of psaM and roaA in Eutreptia viridis, and psaI in Euglena gracilis, suggesting a high level of gene conservation within the euglenoid lineage. Further comparisons with the plastid genomes of closely related green algal taxa have provided additional support for the hypothesis that a Pyramimonas-like alga was the euglenoid chloroplast donor via secondary endosymbiosis.     

Ultrastructural description of Euglena pailasensis (Euglenozoa) from Rincón de la Vieja volcano, Guanacaste, Costa Rica

The euglenoids are unicellular eukaryotic flagellates living in a diversity of soils and aquatic environments and ecosystems. This study describes the ultrastructure of an euglenoid isolated from the surface of a boiling mud pool with temperatures ranging from 38 to 98 degrees C and pH 2 - 4. The hot mud pool is located in Area de Pailas de Barro, Las Pailas, Rincón de la Vieja Volcano, Guanacaste, Costa Rica. The morphological characterization of the Euglena pailasensis was performed by SEM and TEM. It was determined that, although the euglenoid was obtained from an extreme volcanic environment, the general morphology corresponds to that of a typical member of Euglena of 30-45 microm long and 8-10 microm wide, with membrane, pellicle, chloroplasts, mitochondria, nucleus, pigments and other cytoplasmic organelles. E. pailasensis is delimited by a membrane and by 40 to 90 pellicle strips. It was observed up to 5 elongated chloroplasts per cell. The chloroplast contains several osmiophilic globules and a pyrenoid penetrated by few thylakoid pairs. The nutritious material is reserved in numerous small paramylon grains located at the center of the cell, mitocondria are characterized by the presence of crests in radial disposition toward the interior of the lumen. It was also observed around the external surface "pili" like filaments originating from the pellicle strips. There is no evidence for the presence of flagella in the ampulla (reservoir/canal area), a fact confirmed by negative staining, and a difference regarding other species of Euglena. The observed ultrastructural characteristics are not sufficient to explain the adaptation of this species to acid and hot environments.     

Intrageneric Variability Between the Chloroplast Genomes of Trachelomonas grandis and Trachelomonas volvocina and Phylogenomic Analysis of Phototrophic Euglenoids

The latest studies of chloroplast genomes of phototrophic euglenoids yielded different results according to intrageneric variability such as cluster arrangement or diversity of introns. Although the genera Euglena and Monomorphina in those studies show high syntenic arrangements at the intrageneric level, the two investigated Eutreptiella species comprise low synteny. Furthermore Trachelomonas volvocina show low synteny to the chloroplast genomes of the sister genera Monomorphina aenigmatica, M. parapyrum, Cryptoglena skujae, Euglenaria anabaena, Strombomonas acuminata, all of which were highly syntenic. Consequently, this study aims at the analysis of the cpGenome of Trachelomonas grandis and a comparative examination of T. volvocina to investigate whether the cpGenomes are of such resemblance as could be expected for a genus within the Euglenaceae. Although these analyses resulted in almost identical gene content to other Euglenaceae, the chloroplast genome showed significant novelties: In the rRNA operon, we detected group II introns, not yet found in any other cpGenome of Euglenaceae and a substantially heterogeneous cluster arrangement in the genus Trachelomonas. The phylogenomic analysis with 84 genes of 19 phototrophic euglenoids and 18 cpGenome sequences from Chlorophyta and Streptophyta resulted in a well‐supported cpGenome phylogeny, which is in accordance to former phylogenetic analyses.     

Cryptic Speciation in the Genus Cryptoglena (Euglenaceae) Revealed by Nuclear and Plastid SSU and LSU rRNA Gene

The photosynthetic euglenoid genus Cryptoglena is differentiated from other euglenoid genera by having a longitudinal sulcus, one chloroplast, two large trough‐shaped paramylon plates positioned between the chloroplast and pellicle, and lack of metaboly. The genus contains only two species. To understand genetic diversity and taxonomy of Cryptoglena species, we analyzed molecular and morphological data from 25 strains. A combined data set of nuclear SSU and LSU and plastid SSU and LSU rRNA genes was analyzed using Bayesian, maximum likelihood, maximum parsimony, and distance (neighbor joining) methods. Although morphological data of all strains showed no significant species‐specific pattern, molecular data segregated the taxa into five clades, two of which represented previously known species: C. skujae and C. pigra, and three of which were designated as the new species, C. soropigra, C. similis, and C. longisulca. Each species had unique molecular signatures that could be found in the plastid SSU rRNA Helix P23_1 and LSU rRNA H2 domain. The genetic similarity of intraspecies based on nr SSU rDNA ranged from 97.8% to 100% and interspecies ranged from 95.3% to 98.9%. Therefore, we propose three new species based on specific molecular signatures and gene divergence of the nr SSU rDNA sequences.