Assimilatory Filaments Research Articles

The reproductive development of the red alga Actinotrichia fragilis (Galaxauraceae, Nemaliales)

The reproductive structures in Actinotrichia fragilis (Forsskal) Borgesen are described, including the first report of the structure and development of the carpogonial branch and cystocarp for the genus. Tetrasporangia usually arise in a terminal position on assimilatory filaments; occasionally they are formed laterally and in a secund manner. In male thalli, conceptacles are initiated from the apical pit of a thallus branch. Filaments bearing spermatangia issue from the inner face of the conceptacle wall. In female thalli, a carpogonial branch consists of a carpogonium, hypogynous cell and basal cell. Carpogonial branches may arise in two ways, either replacing a vegetative branch or rarely as a third branch between vegetative dichotomous branches. Before fertilization, the hypogynous cell divides to produce four cells. Subsequently, the basal cell produces branched filaments that eventually form the pericarp, which envelops the carpogonial branch and developing gonimoblast. After fertilization, the carp...

Reassessment of the taxonomic status of Elachista tenuis and related species (Elachistaceae, Phaeophyceae), based on culture studies and molecular phylogenetic analyses

The taxonomic status of three closely related species of the brown algal genus Elachista, E. tenuis Yamada, E. sargassicola Noda and E. nipponica Umezaki (Elachistaceae, Ectocarpales sensu lato) was reassessed on the basis of morphological observations including laboratory culture experiments and molecular phylogenetic analyses. These species share characteristic assimilatory filaments of constant width throughout their length except for slightly constricted bases and slightly tapering apices. Although E. sargassicola has been characterized by the presence of phaeophycean hairs, our culture experiments revealed that the presence or absence of such hairs is not a stable taxonomic feature in E. tenuis and E. sargassicola. Furthermore, molecular analyses showed that the rRNA ITS1 and ITS2 regions of E. tenuis and E. sargassicola were nearly identical and grouped them in a strongly supported monophyletic clade. Thus, E. sargassicola should be reduced to synonymy with E. tenuis. On the other hand, E. nipponica, which has been characterized by the production of cylindrical cells in a basal hemispherical cushion, formed cylindrical cells under experimental culture conditions, indicating that the production of such cells is a specific feature of E. nipponica. However, another reported feature of E. nipponica, the production of intercalary plurizoidangia in assimilatory filaments, was rejected, because reexamination of type material revealed that filaments bearing such reproductive structures are referable to Leptonematella fasciculata (Reinke) Silva. Molecular phylogenetic analyses support the distinction of E. tenuis and E. nipponica.

A taxonomic study of the Elachista taeniaeformis complex and E. vellosa from the western Pacific (Elachistaceae, Phaeophyceae)

Three brown algae, Elachista taeniaeformis, Elachista flaccida and Myriactula clavata, which seem to resemble one another in many features and constitute a complex that we call the E. taeniaeformis complex, have been distinguished in the western Pacific by the degree of tapering of the assimilatory filaments, the presence or absence of phaeophycean hairs, and the presence or absence of paraphyses. Morphological observations and laboratory culture experiments based on collections from various localities in Japan indicated that these morphological characters vary, depending on the growing season, experimental culture conditions and age. Molecular-phylogenetic analyses of these and four other elachistacean species, based on ITS regions of the nrRNA gene, showed a close relationship between all samples of the three taxa. Morphological and molecular data indicate that only a single species, E. taeniaeformis, is present within the complex and that genuine E. flaccida should be excluded from the western Pacific marine algal flora. Myriactula clavata is synonymized with E. taeniaeformis, as is Elachista sadoensis. Elachista vellosa is closely related to E. taeniaeformis in the molecular-phylogenetic analyses but is distinguished from it morphologically by having slightly tapering assimilatory filaments with gradually constricted bases.

Morphology and life history of four Japanese species of Elachista (Elachistaceae, Phaeophyceae), including a new record of E. fucicola

SUMMARY Elachista fucicola (Velley) Areschoug (Elachistaceae, Phaeophyceae) is newly recorded from Japan, and compared with three previously described species, Elachista coccophorae Takamatsu, Elachista mollis Takamatsu and Elachista okamurae Yoshida. All species showed direct-type life histories in culture without sexual fusion. Prostrate filaments of E. fucicola formed globular plurilocular zoidangia similar to those reported from Atlantic isolates of this species. However, these were different from uniseriate plurilocular zoidangia of the three Japanese species. Furthermore, the position of a meristematic region in assimilatory filaments and the morphology of paraphyses can easily distinguish these from E. fucicola. Previously emphasized differences in cell length : width ratios in assimilatory filaments showed only slight differences. Elachista coccophorae is characterized by thick-walled assimilatory filaments and curved paraphyses, and the absence of downwardly growing rhizoidal filaments. Elachista mollis and E. okamurae are very similar. However, germlings from plurizoids formed on erect filaments of E. mollis showed characteristic pseudodiscoid growth in culture. Halothrix coccophorae Ohta and Elachista zosterae Noda are reduced to synonyms of E. coccophorae and E. mollis, respectively.

Taxonomic account ofelachista(elachistaceae, phaeophyta) in Korea

A taxonomic and floristic account for Korean Elachista is provided. All previously reported taxa from Korea are reappraised. Elachista in Korea consists of five species: E. falcata Lee sp. nov., E. nipponica Umezaki, E. okamurae Yoshida, E. orbicularis (Ohta) Skiner, and E. tenuis Yamada. Elachista fucicola (Vell.) Aresch. f. typica Rosenvinge sensu Kang (1966) that was previously recorded in Korean flora was assigned to another taxon, E. okamurae Yoshida. Elachista taeniaeformis Yamada is transferred to the new genus, Proselachista Lee et Garbary. Elachista falcata is characterized by having a pseudoparenchymatous medulla, assimilatory filaments with equal diameter over their entire length and small projections on the lower portion, falcate paraphyses, and gourd‐shaped unilocular sporangia.

Trichogloea requienii (Montagne) Kützing (Rhodophyta: Liagoraceae) no litoral do Brasil

O presente trabalho cita a ocorrência de Trichogloea requienii no litoral da Bahia, nordeste do Brasil. O gênero é caracterizado por apresentar calcificação moderada na região entre os filamentos assimiladores (córtex) e medula, células mães dos espermatângios dispostas em verticilos sobre as células subterminais corticais, carpogônio localizado no final do filamento assimilador e desenvolvimento de filamentos estéreis curtos nas células inferiores do ramo carpogonial. São apresentadas descrição e ilustração detalhadas do táxon, além da comparação com entidades afins. Esta é a primeira citação do gênero para o Atlântico Sul.

Freshwater Rhodophyta in Australia: Ptilothamnion richardsii (Ceramiales) and Thorea conturba sp. nov. (Batrachospermales)

Two rare freshwater red algae, Ptilothamnion richardsii Skuja and Thorea conturba sp. nov., are documented from Australia, including the first published photographs of both taxa. The Australian species Ptilothamnion umbracolens (Cribb) Bourrelly nom. illeg. and Anfractutofilum umbracolens Cribb are proposed as heterotypic synonyms of P. richardsii, and additional Australian localities are provided. The family Thoreaceae is reported for the first time in the Australian region. The single population discovered has a vegetative morphology somewhat intermediate between Nemalionopsis and Thorea: assimilatory filaments are sparsely branched and loose, but composed of short cylindrical cells. Reproduction is sexual and similar to that reported for Thorea violacea, except that the carposporangia are smaller and located in the midcortex and the spermatangia are located in the mid- to outer cortex.

Protein crystals in Haplogloia kuckuckii (Chordariales, Phaeophyceae): another mechanism for nitrogen storage in brown algae?

Cellular inclusions up to 18 μm long, with a crystalline outline and periodic substructure, were found in axial filaments of Haplogloia kuckuckii Kylin. Lateral assimilatory filaments did not contain inclusions. Light-microscopic cytochemical tests indicated that the crystals were proteinaceous. Protein-staining procedures, aniline blue-black and chloramine-T Schiff's, produced positive reactions, whereas the periodic acid Schiff's test for carbohydrates gave a negative result. Transmission electron microscopy revealed crystals in the cytoplasm, each one bounded by a membrane that conformed closely to the crystal surface. The crystal matrix had a periodicity of 10 nm. Some crystals showed shells of varying matrix density, possibly representing deposition layers. Crevices and membranous tubules penetrated into the matrix from the crystal surface.The possible ecological significance of nitrogen storage in the form of protein inclusions in this and other brown algae is considered.

Distribution and systematics of the freshwater red algal family Thoreaceae in North America

North American populations and type specimens of Thorea and Nemalionopsis were compared using multivariate morphometrics and image analysis. We continue to recognise the separation of the two genera based on spore-bearing branch-to-assimilatory filament length ratio and assimilatory filament density (≤0·3 and loose for Thorea and ≥0·6 and compressed for Nemalionopsis, respectively). Four species of Thorea were distinguished worldwide: T. hispida (syn. T. andina, T. lehmannii, T. ramosissima), T. violacea (syn. T. bachmannii, T. brodensis, T. gaudichaudii, T. okadae, T. prowsei and T. riekei), T. clavata and T. zollingeri. The former two species have variable branched, non-clavate assimilatory filaments, whereas the latter two have unbranched, clavate assimilatory filaments. Thorea hispida has copious secondary branches while T. violacea is sparsely branched. Thorea clavata is differentiated from T. zollingeri by having fewer monosporangia per cluster. Two of these species were found in North America: T. hispida in Mexico, Grenada and Jamaica, and T. violacea in Texas and Mexico. Two species of Nemalionopsis were differentiated: N. shawii with long assimilatory filaments composed of barrel-shaped cells and n. tortuosa (syn. N. shawii f. caroliniana) with short assimilatory filaments having cylindrical cells. Only N. tortuosa has been collected on the continent, from Florida, Louisiana and North Carolina.

Morphology and life history of Kurogiella saxatilis gen. et sp. nov. (Chordariales, Phaeophyceae)

Kurogiella saxatilis gen. et sp. nov. (Leathesiaceae, Chordariales) is described from the cold-water area of Hokkaido. It grows on exposed rocks in the intertidal zone. K. saxatilis is an annual, appearing in spring and maturing in winter. Erect thalli are pulvinate, solid, rugose, gelatinous and yellowish to dark brown. They are composed of a holdfast, closely packed colourless cylindrical medullary filaments and a cortical layer. The latter consists of 4–8(-11)-celled assimilatory filaments, colourless hairs and ellipsoid or long-lanceolate unilocular sporangia. Each cell contains several discoid chloroplasts with pyrenoids. Plurilocular sporangia are unknown. Kurogiella is closely relatedto Leathesia sect. Primariae, but is distinguished by its much larger, epilithic, solid thallus having almost isodiametric assimilatory filaments. In culture, unispores develop into prostrate filaments, from which pulvinate erect thalli arise directly. Further development of erect thalli occurred under long-day conditions of 5°C and 10°C, and formation of unilocular sporangia occurred under 5°C short-day conditions. The direct type of life history of K. saxatilis, lacking a gametophytic generation, is considered to be an adaptation to the winter field conditions influenced by ice.

Fine structure of the phylogenetically important marine algaRhodogorgon carriebowensis (Rhodophyta, Batrachospermales?)

The fine structure of the recently described red algaRhodogorgon carriebowensis J. Norris et Bucher was studied by light microscopy and scanning and transmission electron microscopy to aid in the ordinal placement of this unusual alga. Most significant in this context were findings that pit plugs had two-layered plug caps, the outer layer of which formed a large dome and was composed of glycoprotein. Cap membranes appeared to be absent. Medullary cells were remarkable in having extremely thick, layered cell walls, whose inward deposition left little room for cytoplasm. Medullary filaments branched little except near the base of the cortex. The assimilatory filaments that made up most of the cortex contained almost all the pigmentation and starch reserves of the thallus. These filaments terminated in either slender apical cells with smooth cell walls or bulbous apical cells bearing spinulose projections. Two types of elongated cells were found in the cortex, those with calcified cell walls and those surrounded by multiple, spreading layers of wall material. Neither cell type was pigmented. The latter type sometimes supported normal assimilatory cells.

The anatomy, life history and development of the Antarctic brown alga Phaeurus antarcticus (Desmarestiales, Phaeophyceae)

Abstract Most aspects of the anatomy, life history and development of Phaeurus antarcticus Skottsberg are typical of the Desmarestiales. Branching is opposite, and the thallus is essentially filamentous in construction. The central axial filament, which comprises cells with thin end walls, and is surrounded by a sheath of narrow filaments, resembles the trumpet hyphae of Desmarestia. The outer surface is covered with assimilatory filaments that arise from cortical cells. Meiosporangia are unusual in that they are catenate, and zoospores develop into dioecious filamentous gametophytes. Female gametophytes consist of very few, relatively large cells, while male gametophytes form more extensive growths of narrower filaments. The oogonia and antheridia are typical of the order. Eggs are released, and in culture frequently remain attached to the oogonial wall. Sporophytes develop from eggs, and also arise apogamously from vegetative cells of female gametophytes. The main axis and primary laterals of sporophyte...

Life history and systematic position of Heteroralfsia saxicola gen. et comb. nov. (Ralfsiaceae, Phaeophyceae)

The phenology, morphology and life history of Saundersella saxicola were studied in culture. At Ohma, Aomori Prefecture, Japan, the species is an annual appearing in March, growing during spring, and maturing in May. In culture, the zoospores show a mediate discal-type of germination, and develop into Ralfsia-like crustose thalli forming intercalary plurilocular sporangia with terminal sterile cells. Erect filamentous thalli develop on the crustose thalli, forming radiate multicellular assimilatory filaments and unilocular sporangia. The following characters of the species suggest its distant systematic relation with Saundersella and rather closer position to Ralfsia and its relatives including Analipus: single sinuate cup-shaped chloroplast without pyrenoid per cell; mediate discal-type of germination; and intercalary plurilocular sporangia with terminal sterile cells. Accordingly, a new genus Heteroralfsia to accommodate the species is proposed.

The structure and reproduction of Patenocarpus paraphysiferus gen. et sp. nov. (Dermonemataceae, Nemaliales, Rhodophyta)

Abstract Patenocarpus paraphysiferus gen. et sp. nov. (Dermonemataceae, Nemaliales) is described from the western Pacific. The carpogonial branch is formed as a lateral branch of an assimilatory filament and is composed of four to five cells. After fertilization, the zygote divides transversely and the upper daughter cell alone takes part in the formation of gonimoblast filaments. Sterile involucral filaments are developed prominently after fertilization. While the gonimoblast filaments are developing, the terminal cell of each neighbouring assimilatory filament produces a paraphysis. The gonimoblast filaments produce horizontal branches which penetrate both the assimilatory filaments and the paraphyses, resulting in a diffuse carposporophyte. Patenocarpus is similar to Liagora (Helminthocladiaceae) and to Yamadaella and Dotyophycus (Dermonemataceae) in both external and internal thallus morphology, but differs from them in its diffuse carposporophyte and the formation of paraphyses in the region of the c...

OBSERVATIONS ON THE LIFE HISTORY OF PAPENFUSSIELLA CALLITRICHA (PHAEOPHYCEAE, CHORDARIALES) IN CULTURE1

ABSTRACTPapenfussiella callitricha (Rosenv.) Kylin from eastern Canada was studied in culture. Zoids from unilocular sporangia develop into microscopic, filamentous, dioecious gametophytes which produce isogametes in filament cells and few‐chambered plurilocular gametangia. Unfused gametes germinate to reproduce the gametophytes. Fusion takes place between a settled (“female”) and a motile (“male”) gamete. The zygote gives rise to a filamentous plethysmothallus that reproduces asexually by zoids formed in thallus cells and in few‐chambered plurilocular zoidangia. Erect macrothalli are produced on the plethysmothallus, beginning with the formation of upright filaments. Later on, these filaments become the terminal assimilators of the macrothalli. Further assimilatory filaments, rhizoids, and unilocular sporangia are produced in a branching region at the base of the terminal assimilator. Zoids from unilocular sporangia formed in culture germinate to reestablish the gametophyte phase. Chromosome counts yielded n = 19 ± 3 for the gametophytes, and 32 ± 6 for the sporophyte, both plethysmothallus and macrothallus.

The life-history ofElachista orbicularis(Ohta) comb. nov. (Elachistaceae, Phaeophyta) in Southern Australia

Elachista orbicularis (Ohta) comb. nov. is newly recorded for southern Australia. It occurs epiphytically on Ecklonia radiata and produces only uniseriate plurilocular sporangia within the cortex; unilocular sporangia are unknown. The zooids settle individually and germinate directly to form new macrothalli. A secondary method of vegetative propagation, in vitro, involves stolon-like behaviour by the long assimilatory filaments, which may form new macrothalli from near their tip. Neither sexual behaviour, i.e. the fusion of zooids, nor the production of unilocular sporangia were induced by the range of temperature and daylength regimes used in these experiments. The life history in southern Australian waters is direct and wholly asexual.

Observations on the morphology and systematics of Chordaria linearis (J. D. Hooker et Harvey) Cotton (Phaeophyta, Chordariales) from Chile

Collections made in southern Chile of the seaweed Chordaria linearis (J. D. Hooker et Harvey) Cotton suggest that it includes a diversity of different forms. These vary most strikingly with respect to branching patterns, the type of assimilatory filaments produced and the size of the unilocular sporangia. It appears that early development is characterized by formation of a tomentose covering of assimilatory hairs causing the plants to resemble species of Papenfussiella or Mesogloia. These hairs are later replaced by shorter cortical filaments. At this time the plants attain the basic structure of Chordaria.

Plurispore development of <i>Cladosiphon okamuranus</i> Tokida (Chordariaceae, Phaeophyta)

Development of plurispores and effects of temperature on their attachment to substrata were studied using mature plurilocular sporangia of Cladosiphon okamuranus Tokida. Development of plurispore showed the disc type, a large number of assimilatory filaments were found to develop from the middle or central part of a disc. These compact and parallel assimilatory filaments formed pseudoparenchyma (multiaxial) with abundant lateral branches. The attachment and development of a plurispore were affected significantly by temperature. Suitable seeding temperature was found to be 17-26º and 26° being optimum for successful attachment. At a temperature over 26ºC, the plurispore could not attach tightly to a substratum or developed poorly.   Key words: Plurispores, Cladosiphon okamuranus, Multiaxial, Hair, Pseudoparenchyma DOI = 10.3329/bjb.v36i2.1505  Bangladesh J. Bot. 36(2): 157-162, 2007 (December)

Ultrastructure of sporophyte of <i>Cladosiphon okamuranus</i> Tokida (Ectocarpales, Phaeophyceae)

Transmission Electron Microscopy of 35 day old culture of Cladosiphon okamuranus Tokida, revealed several chloroplasts and other organelles in each cell of assimilatory filaments. Each chloroplast possesses single pyrenoid and Lipid bodies while in hair cells, there were few chloroplasts clinging to plasma-membrane and many pathholes were seen in the cell wall. Key words: Cladosiphon okamuranus; Brown algae; Ultrastructure; Pathhole DOI: 10.3329/bjb.v38i2.5143 Bangladesh J. Bot. 38(2): 177-180, 2009 (December)

Observations on Kylinia Rosulata From S.W. England

A description is given of the minute epiphytic red alga Kylinia rosulata Rosenv. from collections made in the Plymouth area, and from old herbarium material. The diagnostic characters of this and related species are discussed.The minute epiphytic red alga Kylinia rosulata (order Nemalionales, sub class Florideophycidae) was first described by Rosenvinge (1909) from dried specimens of Sporochnus pedunculatus (Huds.) Ag., collected from the Northern Kattegat. Kylinia was observed on the terminal assimilatory filaments of the supporting plant. Since the original description, this small plant has had a somewhat confused history from both the taxonomic and nomenclatural points of view. Feldmann(1963) has recently summarized the available data, and has verified the validity of the genus and species as originally described by Rosenvinge (see also Feldmann, 1958). K. rosulata is characterized by the possession of short prostrate filaments arising from a single attaching cell, each cell containing a parietal chromatophore, and with male plants bearing a hyaline hair-like body—called the ‘androphore’ by Rosenvinge (1909) and ‘spermatocystophore’ by Feldmann (1958).