TRACHELOMONAS HISPIDA VAR. CORONATA (EUGLENOPHYCEAE). I. ULTRASTRUCTURE OF CYTOSKELETAL AND FLAGELLAR SYSTEMS1,2

Trachelomonas hispida var. coronata Lemm. has a fibrous, mucilaginous, ovoid, mineralized envelope (lorica), the ornamentation and coloration of which are capricious in culture. Cells exhibit a radial distribution of most organelles: (i) A cortical endoplasmic reticulum, (ii) parietal chloroplasts, and (iii) a median vacuolar region surrounded by several Golgi bodies and diverse vesicles. Associated with the emergent flagellum is a “paraflagellar complex” that consists of dense globules, cross-striated ribbon-like structures, a paraflagellar body, and an array of parallel striated filaments. The stigma consists of a single layer of pigmented granules that partially surrounds the canal/reservoir transition zone where microtubular bands intersect. A microtubular cytoskeleton consists of pellicular microtubules, peri-canal microtubules, stigma-associated microtubules and para-reservoir microtubules. The thickenings on the posterior, concave margins of the pellicular strips suggest that this pellicle is of intermediate complexity between those of Euglena spirogyra (Ehrenb. and Trachelomonas volvocina (Ehrenb.).     

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.     

鄂西地区裸藻的新种类

本文报道的是1981年5—6月在鄂西地区(包括五峰、宜都、宜昌、当阳、兴山及神农架林区)采集到的裸藻门植物5个新种,7个新变种和3个新变型。       

PLASTID MORPHOLOGY,ULTRASTRUCTURE, AND DEVELOPMENT IN COLACIUM AND THE LORICATE EUGLENOPHYTES (EUGLENOPHYCEAE)1

Chloroplast morphology was investigated in five species of euglenophytes: Trachelomonas volvocinopsis Swirenko, Strombomonas verrucosa (Daday) Deflandre, Strombomonas costata Deflandre, Colacium mucronatum Bourrelly et Chafaud, and Colacium vesiculosum Ehrenberg. All five species share a common plastid morphotype: disk‐shaped plastids with a pyrenoid that protrudes asymmetrically toward the center of the cell and is capped by a single large grain of paramylon that conforms to the shape of the pyrenoid. Although plastids demonstrated some degree of diversity among the species studied, it was not consistent with current generic boundaries. The plastids of S. verrucosa show a developmental pattern similar to that of Euglena gracilis. The plastids divide during the early portion of the light phase after cell division, and pyrenoids are reduced or absent in dividing plastids. Developmental patterns of plastid replication also suggest that these five taxa share recent common ancestry with members of the genus Euglena subgenus Calliglena.     

ARE CYTOPLASMIC POCKETS (MTR/POCKET) PRESENT IN ALL PHOTOSYNTHETIC EUGLENOID GENERA?1

In 1985, the existence of a cytoplasmic pocket formed from the reservoir membrane in the photosynthetic euglenoid Colacium was described. A band of reinforcing microtubules (MTR) derived from the ventral flagellar root lined the pocket, and a dense fibrillar mesh was associated with the membrane. A comparison of bodonid cytostomes, colorless euglenoid cytostomes, and the reservoir pocket found in Colacium suggested that the three structures were homologous and that photosynthetic euglenoids arose from phagotrophic ancestors. MTR/pockets have since been reported in other photosynthetic euglenoids, including Euglena, Eutreptia, Eutreptiella, Cryptoglena, Tetreutreptia, and Phacus. We found MTR/pockets in three additional taxa, Lepocinclis, Trachelomonas, and Strombomonas, thereby demonstrating the presence of this complex in representatives of all the major photosynthetic genera. A comparison of the MTR/pocket complex across genera indicated a reduction in structural complexity that was consistent with recent phylogenetic schemes based on molecular characters. Three alternative hypotheses of the origin of MTR/pockets in phototrophic euglenoids are presented and discussed.     

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.     

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。     

VARIATIONS IN ENVELOPE MORPHOLOGY AND MINERALIZATION IN TRACHELOMONAS LEFEVREI (EUGLENOPHYCEAE)1

The mineralized envelope surrounding the trachelomonad cell is a complex of organic and inorganic components, anastomosed to form a structure that is characteristic of the species. Although there may be considerable morphological variability in envelope size, shape and ornamentation, its microarchitecture is characterized by two basic components: granular and needle-like deposits. The present study documents for the first time that manipulation of the culture conditions results in predictable changes in envelope ultrastructure, color and elemental composition. Supplemental iron (Fe) in the culture medium results in an increase of granular components in the envelope, whereas supplemental managanese (Mn) results in an increase of needle-like components; with nitrogen (N) supplements there is an increase of both granular and needle-like components in the envelope. It is also shown here that autoxidation of Fe may occur, resulting in the accumulation of Fe deposits along strands of unmineralized envelope mucilage. Autoxidation and deposition of Mn do not occur.     

TRACHELOMONAS HISPIDA VAR. CORONATA (EUGLENOPHYCEAE), II. ENVELOPE SUBSTRUCTURE1,2

Envelopes of the mineralizing protist, Trachelomonas hispida var. coronata Lemm., were examined by light and electron microscopy and by electron diffraction analysis. The ellipsoidal hollow envelope is made of mineralized strands of mucilage (muci-strands) that form a compact wall 0.2–4.0 μm thick, interspersed with numerous puncta 0.2–0.3 μm in diameter and, in some instances with tapered spines ca. 0.6 μm long and 0.7 μm wide at the base. The mucilage strands are cylindrical, anastomosing threads 20 nm thick. Electron-dense, needle-shaped mineral deposits form axial cores in the strands. Also, powdery granular mineral deposits are dispersed sparingly throughout the mucilage matrix. Micromicro-electron diffraction analyses verify the crystalline nature of the needle-shaped deposits, which are 4–9 nm thick and vary in length (20–100 nm). The mucilage strands and microcrystallites pervade the whole of the envelope matrix, including the spines, and may be preferentially oriented along the envelope surfaces.