Light and electron microscope observations on Nephroselmis astigmatica sp. nov. (Prasinophyceae)

Nephroselmis astigmatica sp. nov. is described based on light and electron microscope observations of cultured material, originally collected and isolated from the Natal South Coast, Republic of South Africa. It is characterized by (1) large cell size, (2) absence of a stigma, (3) markedly differentiated anterior part of the cell, (4) possessing two types of flagellar scales in addition to hair scales, (5) possessing four types of body scales and (6) the presence of characteristic pit scales in the flagellar pit. Scale morphology was compared with previously described species, and the morphology of spiny (or stellate) body scales thought to be one of the most useful diagnostic characters in delineating species within the genus. The origin of pit scales is discussed and a similar origin for the third layer of flagellar scales of the type species, N. olivacea Stein is suggested. N. astigmatica shares many ultrastructural features with the type species, including the microtubular flagellar root system consisting of three different roots, one of which is multilayered. The validity of this root system as a generic character is suggested.     

Light and electron microscopical observations on sperm cells of Guizotia abyssinica (Asteraceae)

The sperm cells of Guizotia abyssinica were studied during pollen development by light microscopy and at anther dehiscence by transmission electron microscopy. During development, the nuclei change shape from spherical to elongate, thread-like and banded. They are straight or folded, and rarely spiral-shaped when present in the pollen tube. Electron microscopy disclosed that the elongated sperm nuclei are apparently lobate. Intermittently, they are constricted and attenuated or convoluted. The major part of the sperm chromatin is condensed and peripheral, while a minor part is dispersed and central. The scanty sperm cytoplasm contains mitochondria and starch granules. The cytoplasm is mainly restricted to spaces adjoining constricted, lobed and convoluting nuclear sites. Some cytoplasmic patches become embayed in the nucleus at these sites. The periplasm bordering the sperm cells may originate from lucid dilations of the lumen between the plasma membranes of the sperm and vegetative cells. The periplasm is sometimes partially or entirely surrounded by double-membraned endoplasmic reticulum. Folded sperm cells with less coherent periplasm possibly represent a late stage preceding discharge into the pollen tube. The sperm cells always precede the vegetative nucleus into the pollen tube.     

Light and electron microscopical studies onHafniomonas gen. nov. (Chlorophyceae,Volvocales), a genus resemblingPyramimonas (Prasinophyceae)

Based on light and electron microscopical studies ofPyramimonas reticulata the genusPyramimonas is shown to contain a number of unrelated flagellates.P. reticulata andP. montana are transferred to the new genusHafniomonas, cells of which differ fromPyramimonas in shape, in the absence of scales and hairs on the body and flagellar surfaces, in details of the chloroplast, the position of the nucleus, the Golgi apparatus, the internal structure of the flagellar apparatus, and in cell division. The prasinophytePyramimonas contains a characteristic association of a large microbody and a rhizoplast, situated on the nuclear surface. A similar association is being found in an increasing number of prasinophycean flagellates, but is absent inHafniomonas, which is considered related to chlorophycean rather than prasinophycean flagellates. The phylogenetic position ofHafniomonas is discussed, based in particular on details of the unique flagellar apparatus.     

Phylogeny of Rosellinia capetribulensis sp. nov. and its allies (Xylariaceae)

A new Rosellinia species, R. capetribulensis isolated from Calamus sp. in Australia is described. R. capetribulensis is characterized by perithecia immersed within a carbonaceous stroma surrounded by subiculum-like hyphae, asci with large, barrel-shaped amyloid apical apparatus and large dark brown spores. Morphologically, R. capetribulensis appears to be similar to R. bunodes, R. markhamiae and R. megalospora. To gain further insights into the phylogeny of this new taxon we analyzed the ITS-5.8S rDNA using maximum parsimony and likelihood methods. In addition, a morphological dataset also was analyzed phylogenetically to investigate possible affinities. ITS rDNA based phylogenies reveal that R. capetribulensis is closely related to other Rosellinia species showing closest affinity to R. arcuata, RL necatrix and R. pepo. However, analysis of R. capetribulensis forms an unsupported branch sister to these taxa. Results from the morphological matrix indicate a close morphological affinity to members of Rosellinia subgenus Rosellinia. Despite that ITS rDNA and morphological analyses present difficulties in constructing a proper phylogenetic framework among Rosellinia and allied genera, there is sufficient evidence to support the establishment of the new taxon in the genus Rosellinia. The morphological similarities and differences between R. capetribulensis and allied genera such as Astrocystis and Entoleuca are also briefly discussed.     

potamolejeunea Holtii (Spruce) nov.comb.

Abstract

Bryophytes usually have anti-feeding properties to defend against microbial and herbivore attack; however, the consumption of Haplocladium microphyllum (Hedw.) Broth. capsules by Agrotis sp. larvae is rather common in Shanghai in the spring. To test whether H. microphyllum is the only moss eaten, and why the gametophytes of H. microphyllum are not eaten, a series of quantitative experiments were carried out to understand the feeding habits of Agrotis larvae on the given moss materials at three growth stages of larval life. The results show that the larvae can feed on the capsules of six moss species to different degrees: Funaria hygrometrica Hedw., H. microphyllum, Physcomitrium sphaericum (C.F.Ludw. ex Schkuhr) Brid., Trematodon longicollis Michx., Ditrichum pallidum (Hedw.) Hampe, and Pogonatum inflexum (Lindb.) Sande Lac. The capsules of the first four species were grazed heavily by the larvae, compared with limited consumption of the latter two (D. pallidum and P. inflexum), which even induced a high mortality rate among the larvae. With the growth of the larval instar, the daily demand for moss capsules by the larvae increases gradually. The lipid content of the capsules may play an important role when the larva selects its feeding target.     

Culture studies of Acrochaete leptochaete comb. nov. and A. wittrockii comb. nov. (Chaetophoraceae, Chlorophyceae)

A culture study of the plants known as Phaeophila leptochaete (Huber) Nielsen and P. wittrockii (Wille) Nielsen proved that these are distinct species. Both have the Acrochaete type of hairs, and therefore, the new combinations Acrochaete leptochaete and A. wittrockii are introduced. Several isolates of both species were started from plants collected at different places in Europe.
A. leptochaete in culture was mainly characterised by having two or more (up to six) pyrenoids in many of its cells, while in A. wittrockii there invariably was only one. The swarmers formed by A. leptochaete had two or four flagella. Several hairs from one basal swelling were sometimes observed in one of the isolates. Another isolate often formed a hair on the germinated zoospore. The isolates of A. wittrockii had a variable morphology, from unicellular plants to large pseudoparenchymatous cell masses. Different kinds of swarmers were observed; zoospores with three flagella seemed typical, but ones with two or four flagella were also observed. Small, pale biflagellate swarmers were assumed to be gametes. One of the isolates of A. wittrockii differed from the rest as the only swarmer type observed was zoospores with two flagella. Chlorophilum ephemerum is considered identical to A. wittrockii. Observations on hair formation in A. repens suggested that the hair structure represents a separate cell.     

Nebela tuberculata comb. nov. (Arcellinida), its History and Ultrastructure

SYNOPSIS. The name Nebela tuberculata comb. nov. is proposed for the testate ameba formerly known as Difflugia tuberculata (Wallich, 1864) Archer, 1867. The generic reassignment is based upon the test construction material which is shown, by electronmicrographs and X-ray diffraction, to be autogenous regular and irregular silicious rods. A brief history of the animal is recounted utilizing works of several authors who have encountered the ameba over the last century.     

Systematic study of the genus Acetobacter with descriptions of Acetobacter indonesiensis sp. nov., Acetobacter tropicalis sp. nov., Acetobacter orleanensis (Henneberg 1906) comb. nov., Acetobacter lovaniensis (Frateur 1950) comb. nov., and Acetobacter estunensis (Carr 1958) comb. nov

Thirty-one Acetobacter strains obtained from culture collections and 45 Acetobacter strains isolated from Indonesian sources were investigated for their phenotypic characteristics, ubiquinone systems, DNA base compositions, and levels of DNA-DNA relatedness. Of 31 reference strains, six showed the presence of ubiquinone 10 (Q-10). These strains were eliminated from the genus Acetobacter. The other 25 reference strains and 45 Indonesian isolates were subjected to a systematic study and separated into 8 distinct groups on the basis of DNA-DNA relatedness. The known species, Acetobacter aceti, A. pasteurianus, and A. peroxydans are retained for three of these groups. New combinations, A. orleanensis (Henneberg 1906) comb. nov., A. lovaniensis (Frateur 1950) comb. nov., and A. estunensis (Carr 1958) comb. nov. are proposed for three other groups. Two new species, A. indonesiensis sp. nov. and A. tropicalis sp. nov. are proposed for the remaining two. No Indonesian isolates were identified as A. aceti, A. estunensis, and A. peroxydans. Phylogenetic analysis on the basis of 16S rDNA sequences was carried out for representative strains from each of the groups. This supported that the eight species belonged to the genus Acetobacter. Several strains previously assigned to the species of A. aceti and A. pasteurianus were scattered over the different species. It is evident that the value of DNA-DNA relatedness between strains comprising a new species should be determined for the establishment of the species. Thus current bacterial species without data of DNA-DNA relatedness should be reexamined for the stability of bacterial nomenclature.     

Ptilagrostis milleri comb. nov. (Poaceae: Stipeae)

Based on a comparison of the macro‐morphology and lemma micro‐morphology, Stipa milleri Noltie is transferred to Ptilagrostis Griseb. as P. milleri (Noltie) M. Nobis & A. Nobis. Lemma epidermal patterns in the examined species are presented and discussed.     

Tetraselmis wettsteinii (Schiller) Throndsen comb. nov. and its occurrence in golfo di Napoli

Abstract

Carteria wettsteinii Schiller (1913) has been isolated from Golfo di Napoli and investigated by means of electron microscopy which revealed micro-anatomical features characteristic of the genus Tetraselmis. The species is commonly present in Golfo di Napoli during summer with cell numbers 10²–10⁶ cells-litre^?1, occasionally producing blooms of 10⁷ cells·litre^?1.     

Further studies on Nephroselmis and its allies (Prasinophyceae). II. Mamiella gen. nov., Mamiellaceae fam. nov., Mamiellales ord. nov.

The marine prasinophycean flagellate presently known as Nephroselmis gilva has been examined, using both the type culture and material from temperate (Denmark, New Zealand) and tropical waters (Thailand). All cell surfaces are covered with unmineralized scales, two types on the body, two on the flagella including flagellar hairs. The detailed structure of the scales is described, using high power electron microscopy of detached positive–stained scales. Previously overlooked organelles within the cell include large numbers of extrusive bodies, a rare type of organelle in chlorophyll–a– and –b–containing organisms, and an eyespot. N. gilva differs profoundly from the type species of Nephroselmis , and is transferred to the new genus Mamiella. Mamiella gilva is closely related to Mantoniella squamata. Together with the genus Dolichomastix they form the new family, Mamiellaceae, a small group of marine flagellates of worldwide distribution.
The members of the new family probably represent the most primitive extant prasinophytes. When compared with other members of the class, its species stand out, particularly by the lack of small square or diamond–shaped scales on the flagella and cell body. It is suggested that the Mamiellaceae should be referred to a separate order, Mamiellales.     

Light and electron microscopical investigations on shell pores (caeca) of fissurellid limpets (Mollusca: Archaeogastropoda)

The organic content (caecum) of the shell pores of five species of fissurellid (key-hole) limpets was investigated by means of light and electron microscopy. Fissurellid caeca are unbranched, polycellular extensions of the mantle epithelium, which penetrate the whole shell and contact the periostracum via organic fibres called 'brush'. They are built up by two cell-types, which enclose a central lumen, and are formed concurrently with the shell itself. Because of fundamental structural and developmental differences, the superficially similar shell pores of bivalves (caeca) and polyplacophorans (aesthetes) are considered as analogous rather than homologous organs. Similarities are found with brachiopod caeca, probably owing to similar functions.     

Ultrastructure and molecular phylogeny of thaumatomonads (Cercozoa) with emphasis on Thaumatomastix salina from Oslofjorden, Norway

A culture of Thaumatomastix was isolated from a sediment sample collected in Oslofjorden and established as a monospecific strain (UIO286). Based on this culture, light and transmission electron microscopy and phylogenetic analyses were carried out. Thaumatomastix species are confined within the order Thaumatomonadida of the class Imbricatea and phylum Cercozoa. They are heterotrophic and their cell bodies are covered with silica scales. Observations of thin sections as well as whole mounts indicate that the morphology and ultrastructure of UIO286 is identical to T. salina, which was initially described from salt pools in Denmark. Detailed examination revealed some new features such as the presence of pseudopodia and silica deposition vesicles producing spine scales. The phylogeny presented here includes ribosomal DNA sequences from both imbricatean cultures and environmental samples. The 18S rDNA phylogenetic tree suggests that (i) Thaumatomastix is paraphyletic within the Thaumatomonadida clade, (ii) there is no close affinity between T. salina and other cultured and sequenced strains, but it is closely related to a sequence obtained from environmental DNA; we propose the present strain to serve as a reference culture of Thaumatomastix species and T. salina. Further, we discuss the distribution, habitats, and evolution of scale formation among euglyphids and thaumatomonads.     

Elevation of Francisella philomiragia subsp. noatunensisMikalsen et al. (2007) to Francisella noatunensis comb. nov. [syn. Francisella piscicida Ottem et al. (2008) syn. nov.] and characterization of Francisella noatunensis subsp. orientalis subsp. nov., two important fish pathogens

Aims: This study was conducted to clarify the taxonomic status of Francisella sp. strain Ehime‐1, a fish pathogen, in relation to the fish pathogens F. piscicida and F. philomiragia subsp. noatunensis and to F. philomiragia subsp. philomiragia. Methods and Results: Francisella sp. Ehime‐1 was compared to F. piscicida, F. philomiragia subsp. noatunensis and several F. philomiragia subsp. philomiragia isolates through sequencing of the 16S rRNA‐gene and several house‐keeping genes and determination of biochemical and phenotypic properties. Results show that F. piscicida is indistinguishable from F. philomiragia subsp. noatunensis by sequence and phenotypic traits. Francisella sp. Ehime‐1 and F. philomiragia subsp. noatunensis are clearly separated from F. philomiragia. Francisella sp. Ehime‐1 is biochemically, phenotypically and genetically different from F. philomiragia subsp. noatunensis (=F. piscicida), but DNA–DNA hybridization does not clearly support establishment as a separate species (level of relatedness 64% and 73·4%, mean 68·7%). Conclusions: We propose to elevate F. philomiragia subsp. noatunensis to species rank as F. noatunensis comb. nov., while F. piscicida is considered a heterotypic synonym of F. noatunensis comb. nov. Evidence suggests that Francisella sp. Ehime‐1 represents a novel subspecies of F. noatunensis, for which the name F. noatunensis subsp. orientalis subsp. nov. is proposed (=DSM21254^T, = LMG24544^T). Significance and Impact of the Study: This study contributes to the taxonomy and characteristics of fish‐pathogenic Francisella spp.