Filamentous Thalli Research Articles

Morphology of filamentous thalli of Analipus japonicus (Ralfsiales), temperature and irradiance effects on their formation and growth, and erect thallus formation in the field

Free-living filamentous thalli derived from an Analipus japonicus erect thallus were established in laboratory culture. The filamentous thalli were composed of slender filaments and densely pigmented oval or sub-oval cell masses. Temperature (5–20 °C) and irradiance (25–200 μmol photons m−2 s−1) effects on formation and growth of the thalli from three explant groups (isolated filaments, small cell masses, and large cell masses) were investigated for 15 days. These explants survived over the examined range. The isolated filaments had a high ability to form the thalli, and the isolated and new filaments formed filaments and cell masses. Meanwhile, the isolated and new cell masses formed only filaments, and their ability to grow and form the thalli decreased as they grew in size. Optimum culture conditions for formation and growth of the thalli from the isolated filaments, and the two cell mass growths were 15–20 °C and 100–200 μmol photons m−2 s−1. To produce erect thalli, the filamentous thalli were cultured on seedling threads for 6 weeks at 15 °C, 60 μmol photons m−2 s−1 and 20 cm s−1 water flow velocity. Erect axis density increased with increasing coverage of the filamentous thalli, and their cell masses (primordia of erect thallus holdfast) with mean area of about 140 × 103 μm2 began to produce erect axes. After 4 months of field cultivation, they grew into full-grown erect thalli of about 20 cm long. These findings show that the free-living filamentous thalli were applicable for stable seedling production of A. japonicus to be used in aquaculture.

<p><strong><em>Centroceras gasparrinii</em></strong><strong> subsp. <em>minor</em> subsp. nov. (Ceramiaceae, Rhodophyta) in the North Adriatic Sea (Mediterranean): molecular and morphological characterization</strong></p>

Centroceras Kützing is a small red algal genus with 18 currently accepted species (Guiry & Guiry 2019), characterized by simple filamentous thalli with erect axes arising from a prostrate system and di-trichotomous branching (Hommersand 1963). The characters used to distinguish species are primarily cortical filament morphology: shape and number of the acropetal cortical cells, shape of gland cells, and shape of spines (Won et al. 2009). The generitype C. clavulatum (C. Agardh) Montagne has been viewed for a long time as a highly variable and cosmopolitan species (Hommersand 1963). Molecular and detailed morphological analyses brought Barros-Barreto et al. (2006) to report that C. clavulatum may consist of a species complex and Won et al. (2009) confirmed this hypothesis identifying eight taxonomic entities phylogenetically segregated from genuine C. clavulatum. Seven of these entities were assigned to the following species: C. gasparrinii (Meneghini) Kützing, C. hommersandii Won, T.O. Cho & Fredericq, C. hyalacanthum Kützing, C. micracanthum Kützing, C. natalensis Won, T.O. Cho & Fredericq, C. rodmanii Won, T.O. Cho & Fredericq, and C. tetrachotomum Won, T.O. Cho & Fredericq, (Won et al. 2009). Centroceras gasparrinii, C. hyalacanthum, and C. micracanthum are three western Atlantic species listed as synonyms of C. clavulatum since the middle of the 19th century and resurrected from the ‘C. clavulatum complex’ by Won et al. (2009). In particular, two of these taxa were described from specimens of the Mediterranean Sea: C. gasparrinii (as Ceramium gasparrinii Meneghini, type locality Palermo, Italy) and C. micracanthum (reported with the synonym Centroceras leptacanthum Kützing, type locality Genoa, Italy). Therefore, the numerous Mediterranean records of C. clavulatum (e.g., Gómez Garreta et al. 2001; Verlaque 2001; Sfriso & Curiel 2007; Taşkýn et al. 2013) most probably belong to one of these two species and have to be re-examined for a correct identification and to understand the spatial distribution of the different taxa (Tsiamis et al. 2010). For this reason, in the last years in Greece (Tsiamis et al. 2010), Spain (Gallardo et al. 2016) and Morocco (Hassoun et al. 2018) accurate sampling and morphological analyses of specimens previously identified as C. clavulatum were conducted to determine their correct taxonomic identities. In all cases the recognized species was C. gasparrinii, which can be distinguished morphologically from the other ones previously known as C. clavulatum by the presence of ovoid gland cells and ovoid terminal acropetal cortical cells (Won et al. 2009). As reported by Tsiamis et al. (2010), Greek samples differed from those described by Won et al. (2009), in the smaller number of periaxial cells (10–12 against 13–19).

Diversity, biogeography and host specificity of kelp endophytes with a focus on the genera Laminarionema and Laminariocolax (Ectocarpales, Phaeophyceae)

ABSTRACTEndophytic filamentous brown algae are known to invade stipes and fronds of kelps with potentially negative effects for the hosts. They have simple filamentous thalli and are difficult to identify based on morphology. We investigated the molecular diversity of 56 endophytes isolated from seven different kelp species from Europe, Chile, Korea and New Zealand by sequencing two unlinked molecular markers (5’COI and ITS1). A majority of 49 of the isolated endophytes (88%) belonged to the genera Laminarionema and Laminariocolax. The endophyte Laminarionema elsbetiae was isolated from Saccharina latissima and S. japonica tissues in Europe and Korea, respectively, and showed highly similar sequences in both regions. Three different species of the genus Laminariocolax were identified, the most common of which was L. aecidioides, an endophyte with a worldwide distribution and a broad host range. The other two species, L. tomentosoides and a species described here as Laminariocolax atlanticus sp. nov., were associated with different kelp species in the northern hemisphere and the North Atlantic, respectively. Our results suggest that specific host-endophyte patterns could exist locally, as found in kelps in Brittany where all endophytes isolated from S. latissima were L. elsbetiae, all endophytes isolated from Laminaria digitata were Laminariocolax tomentosoides, and those isolated from Laminaria hyperborea were Laminariocolax atlanticus and L. aecidioides. However, this pattern was not consistent with the results from other places, such as Western Scotland and Helgoland where the same kelp species are present.

New Taxa of Streptophyte Algae (Streptophyta) from Terrestrial Habitats Revealed Using an Integrative Approach

Two new genera (Streptosarcina and Streptofilum) and three new species (Streptosarcina arenaria, S. costaricana and Streptofilum capillatum) of streptophyte algae were detected in cultures isolated from terrestrial habitats of Europe and Central America and described using an integrative approach. Additionally, a strain isolated from soil in North America was identified as Hormidiella parvula and proposed as an epitype of this species. The molecular phylogeny based on 18S rRNA and rbcL genes, secondary structure of ITS-2, as well as the morphology of vegetative and reproductive stages, cell ultrastructure, ecology and distribution of the investigated strains were assessed. The new genus Streptosarcina forms a sister lineage to the genus Hormidiella (Klebsormidiophyceae). Streptosarcina is characterized by packet-like (sarcinoid) and filamentous thalli with true branching and a cell organization typical for Klebsormidiophyceae. Streptofilum forms a separate lineage within Streptophyta. This genus represents an easily disintegrating filamentous alga which exhibits a cell coverage of unique structure: layers of submicroscopic scales of piliform shape covering the plasmalemma and exfoliate inside the mucilage envelope surrounding cells. The implications of the discovery of the new taxa for understanding evolutionary tendencies in the Streptophyta, a group of great evolutionary interest, are discussed.

Preliminary comparison of atmospheric CO2 enhancement to photosynthesis of Pyropia yezoensis (Bangiales, Rhodophyta) leafy thalli and filamentous thalli

SUMMARYIntertidal macroalgae are submerged in seawater at high tide and exposed to air at low tide. When they are exposed to the air, CO2 is the main inorganic carbon source. In this study, the photosynthetic performances of PSI and PSII were measured in different generations of Pyropia yezoensis (leafy thalli and filamentous thalli) that had been exposed to air containing different CO2 concentrations. Changes in photosynthesis during dehydration and salt treatment under the different CO2 concentrations were also analyzed. The results showed that in leafy thalli, the effective photochemical quantum yield of PSII (YII) was enhanced as CO2 increased, which suggested that CO2 assimilation was enhanced and that they can utilize CO2 in the air directly, even when they are subjected to moderate stress. These findings could explain why, in P. yezoensis aquaculture, moderate exposure to air does not lead to a decrease in crop yield. However, in filamentous thalli, there were no significant differences in YII at the CO2 concentrations tested. The expression of genes involved in the Calvin cycle in leafy thalli was higher than that in filamentous thalli. CO2 uptake and biomass of P. yezoensis leafy thalli is larger than filamentous thalli, which may be due to its different carbon utilization mechanism and the adaptation of intertidal environment in the evolutionary process.

Life history bias in endophyte infection of the Antarctic rhodophyte, Iridaea cordata

Abstract Endophytic organisms are known to have varied effects on their host organism in terrestrial and marine environments. In previous studies on marine algae, these symbioses range from innocuous to pathogenic depending on the host and endophyte species. The present study further assessed a pathogenic relationship between filamentous algal endophytes and a red algal host from the western Antarctic Peninsula. We analyzed endophyte presence (appearance of filamentous thalli) in the three life history stages of Iridaea cordata and potential impacts on fertility in the fertilized female gametophytes (carposporophytes) and tetrasporophytes. We found that endophytes proliferate throughout significantly more thallus area in tetrasporophyte and unfertilized gametophyte hosts than in carposporophyte hosts, but there was no correlation between endophyte cover and fertility in these individuals. This study also provides a demographic analysis of I. cordata populations surrounding Palmer Station, Antarctica, showing that these populations are haploid dominated (∼78% of individuals). The differential presence of filamentous algal endophytes indicates that endophyte pathogenicity indirectly has greater effect on tetrasporophytes and unfertilized gametophytes than on the carposporophytes, which house the products of sexual recombination.

Molecular diversity of green corticolous microalgae from two sub-Mediterranean European localities

Green algae in corticolous biofilms are simple coccoid cells or filamentous thalli with strikingly low morphological diversity. Consequently, microscopic identification of these organisms is difficult, and often possible only to higher taxonomic units. We investigated the taxonomic and phylogenetic composition of green microalgae isolated from biofilms growing on the bark of Quercus pubescens and Pinus nigra. The study was based on 122 partial sequences of the plastid-encoded rbcL gene. In total, 29 operational taxonomic units (OTUs), differing in their rbcL sequences, were encountered. Members of the Trebouxiophyceae formed 97.5% of the isolates; Streptophyta made up 2.5%. The most frequently occurring OTUs were in the genera Coccomyxa, Parachloroidium and Stichococcus. Within the Watanabea clade, we have probably discovered an as-yet undescribed generic lineage with chlorelloid morphology. OTUs belonging to the recently described trebouxiophycean genera Kalinella, Leptochlorella and Xylochloris were also encountered, which indicates that these genera are probably widely distributed in subaerial microhabitats, such as tree bark. The samples taken from oak trees were more diverse in their OTU composition than those taken from pine trees, but the average phylogenetic distances of OTUs in samples did not differ between the host tree taxa. Host tree species had a stronger effect on the community structure of algae than the sampling locality. This indicates that habitat filtering is important for the distribution of individual microalgal phylogenetic taxa.

Characterization of the AOX gene and cyanide-resistant respiration in Pyropia haitanensis (Rhodophyta)

In order to characterize the structure and function of the alternative oxidase (AOX) gene in Pyropia haitanensis, full-length complementary DNA (cDNA) of the locus (denoted as PhAOX) was obtained by in silico cloning, rapid amplification of cDNA ends, and reverse transcription PCR. The PhAOX sequence was 3,192 bp including a 5′-untranslated region (UTR) of 1,484 bp, a 3′-UTR of 274 bp, and an open reading frame of 1,434 bp predicted to encode a protein of 477 amino acids with a molecular mass of 50.47 kDa and a putative isoelectric point of 9.75. PhAOX is predicted to be a precursor protein with mitochondrial-targeting peptides. The deduced amino acid sequence of PhAOX was most similar to PyAOX from Porphyra (= Pyropia) yezoensis (77 % identity); however, gene sequences from PhAOX and PyAOX showed obvious divergence. PhAOX had a 315-bp intron but PyAOX had no intron. Expression of mRNA in filamentous thalli and the foliose thallus, which are different life cycle stages, was examined by real-time fluorescent quantitative PCR (qPCR). The highest PhAOX expression was in filamentous thalli and was about 10 times the expression in the foliose thallus. We showed that an alternative respiration pathway also existed in P. haitanensis using a noninvasive microsensing system. The contribution of the alternative pathway to total respiration in filamentous thalli was greater than the contribution in the foliose thallus. This result was consistent with the level of PhAOX gene expression observed in different life cycle stages.

Distribution patterns of subaerial corticolous microalgae in two European regions

Subaerial micro-algal biofilms growing on tree bark are omnipresent in a variety of ecosystems. However, terrestrial microhabitats have traditionally attracted far less attention from phycologists than marine and freshwater habitats, so their diversity and community structure is still very poorly known (Freystein & Reisser 2010, Rindi et al. 2010). Because of the lack of suitable discriminating characters and because species concepts are poor, species-level microscopic identification of most subaerial algae and Cyanobacteria is complicated (Ettl & Gartner 1995). In comparison to that of planktic and benthic communities, the morphological diversity of terrestrial microalgae is strikingly low; most taxa have coccoid spherical to oval cells, or simple filamentous thalli (Hoffmann 1989, Ettl & Gartner 1995). Consequently, most microscopic studies of subaerial assemblages have been based on either limited datasets acquired from approximate morphological identification of cultured strains (e.g. Nakano et al. 1991, Neustupa & Skaloud 2008), or direct observations of natural samples. Research on natural samples has typically been concentrated on several conspicuous groups, such as Trentepohliales, Klebsormidium, and Prasiola (e.g. Rindi & Guiry 2004, Hedenas et al. 2007). Recent molecular studies of subaerial microalgae have mostly been focused on phylogenetics and taxonomy of new and little-known microalgal and cyanobacterial lineages thriving in these microhabitats (Rindi et al. 2006, Zhang et al. 2008, Neustupa et al. 2013). They illustrated that the real phylogenetic diversity of subaerial microalgae was probably grossly underestimated by traditional morphological taxonomy. Molecular data revealed that the micro-algal communities of these habitats include numerous as yet unknown phylogenetic taxa. Some have been described as new micro-algal genera, such as Spongiochrysis, Heveochlorella, Hylodesmus, and Leptochlorella (Rindi et al. 2006, Zhang et al. 2008, Elias et al. 2010, Neustupa et al. 2013). Despite methodological limitations, microscopy still provides the very core of current knowledge on ecology and distribution patterns of subaerial algae, including those in corticolous biofilms. Tropical corticolous biofilms are often

Variations of morphology and photosynthetic performances of Ulva prolifera during the whole green tide blooming process in the Yellow Sea

Since 2007, the world's largest macroalgal blooms have occurred along the coastal area of the Yellow Sea for 6 consecutive years. In 2012, shipboard surveying and satellite remote sensing were used to monitor the whole blooming process. The blooms originated in Rudong sea area of the South Yellow Sea where bloom patches were of dark green and filamentous thalli were the dominant morphology. The scale of the blooms reached its peak size in Rizhao sea area of the North Yellow Sea, and decreased promptly and became insignificant in Qingdao coast where the blooms turned yellow, mostly with air sac blades. Meanwhile, vegetative cells of the green tide algae changed into cytocysts gradually from which germ cells were released as the blooms drifted northward. Additionally, chlorophyll contents and fluorescence activity of free-floating thalli in the North Yellow Sea were both significantly lower than that in the South Yellow Sea. Those studies presented here contributed to increasing our understanding about how the green tide declined gradually in the North Yellow Sea.

Effects of UV-B Radiation and Periodic Desiccation on the Morphogenesis of the Edible Terrestrial Cyanobacterium Nostoc flagelliforme

The terrestrial cyanobacterium Nostoc flagelliforme Berk. et M. A. Curtis has been a popular food and herbal ingredient for hundreds of years. To meet great market demand and protect the local ecosystem, for decades researchers have tried to cultivate N. flagelliforme but have failed to get macroscopic filamentous thalli. In this study, single trichomes with 50 to 200 vegetative cells were induced from free-living cells by low light and used to investigate the morphogenesis of N. flagelliforme under low UV-B radiation and periodic desiccation. Low-fluence-rate UV-B (0.1 W m(-2)) did not inhibit trichome growth; however, it significantly increased the synthesis of extracellular polysaccharides and mycosporine-like amino acids and promoted sheath formation outside the trichomes. Under low UV-B radiation, single trichomes developed into filamentous thalli more than 1 cm long after 28 days of cultivation, most of which grew separately in liquid BG11 medium. With periodic desiccation treatment, the single trichomes formed flat or banded thalli that grew up to 2 cm long after 3 months on solid BG11 medium. When trichomes were cultivated on solid BG11 medium with alternate treatments of low UV-B and periodic desiccation, dark and scraggly filamentous thalli that grew up to about 3 cm in length after 40 days were obtained. In addition, the cultivation of trichomes on nitrogen-deficient solid BG11 medium (BG11(0)) suggested that nitrogen availability could affect the color and lubricity of newly developed thalli. This study provides promising techniques for artificial cultivation of N. flagelliforme in the future.

CHARACTERIZATION OF THE ALTERNATIVE OXIDASE GENE IN PORPHYRA YEZOENSIS (RHODOPHYTA) AND CYANIDE-RESISTANT RESPIRATION ANALYSIS(1).

The full-length cDNA of the alternative oxidase (AOX) gene from Porphyra yezoensis Ueda (PyAOX) [currently assigned as Pyropia yezoensis (Ueda) M. S. Hwang et H. G. Choi (http://www.algaebase.org)] an ancient member of the Rhodphyta, was cloned by electronic cloning, rapid amplification of cDNA ends (RACE), and reverse transcription PCR. The nucleotide sequence of PyAOX consists of 1,650 bp, including a 5' untranslated region (UTR) of 170 bp, a 3' UTR of 148 bp, and an open reading frame (ORF) of 1,332 bp that can be translated into a 443-amino-acid residue with a molecular mass of 47.33 kDa and a putative isoelectric point (pI) of 9.71. The putative amino acids had 50%-61% identity with AOX genes in Eukaryota and higher plants and had AOX-like characteristics. The expression of PyAOX mRNA in different stages of the life cycle, conchospores, filamentous thalli (conchocelis stage), and leafy thalli, was detected by real-time quantitative PCR (qPCR). The highest level of expression, which was observed in filamentous thalli, was three times higher than that observed in leafy thalli. The next highest level, which was observed in the conchospores, was twice as high as that observed in leafy thalli. We showed that an alternative respiration pathway existed in P. yezoensis with a noninvasive microsensing system. The contribution of the alternative pathway to total respiration in filamentous thalli was greater than that in leafy thalli. This result was consistent with the level of AOX gene expression observed in different stages of the life cycle.

Detection of Epigenetic Variations in the Protoplast-Derived Germlings of Ulva reticulata Using Methylation Sensitive Amplification Polymorphism (MSAP)

Regeneration of protoplasts into de novo plants was reported for a large number of seaweed species. The regeneration of protoplasts into different morphotypes as a result of epigenetic variations was discussed for the first time in this study. The loci assessed for methylation modifications in normal filamentous thalli showed a frequency of 32.43% as unmethylated DNA, 24.32% as a hemimethylated, and 20.27% as a methylation of internal cytosine at both the strands. The corresponding methylation values for disk-type thalli were 27.02%, 32.43%, and 14.86%, respectively. The hypermethylation condition was apparent in the disk-type thalli with methylation ratio of 72.97% compared to that of normal filamentous thalli with 67.56%. The frequency of methylation polymorphic sites among the two morphotypes was 53%. The present study reveals the distinct expression of cytosine methylation and is thus correlated to differential morphogenesis of plants regenerated from cultured cells. The number of protoplasts regenerating into filamentous thalli declined with increasing temperature from 15°C, 20°C, 25°C, and 30°C. The disk-type variant had higher thermal stability at 30°C over normal filamentous thalli. Further, this variant could maintain itself for more than a year in the laboratory indicating its suitability for in vitro germplasm maintenance and propagation.Electronic supplementary materialThe online version of this article (doi:10.1007/s10126-012-9434-7) contains supplementary material, which is available to authorized users.

A first assessment of Galapagos basidiolichens

As part of an ongoing comprehensive inventory of Galapagos lichens, a first assessment of the morphology and anatomy of basidiolichens from the archipelago is presented here. It is the basis for further studies of the taxonomy, ecology and biogeography of this poorly known group of lichens. Four genera, all in Hygrophoraceae, can be distinguished: Acantholichen, Cora, Cyphellostereum and Dictyonema. Both Acantholichen and Cora are characterized by chroococcoid cyanobionts and a heteromerous thallus with a distinct upper cortex and photobiont layer. The monotypic Acantholichen pannarioides is entirely composed of small, branched, inflated squamules that appear densely pruinose because their cortical hyphae bear characteristically swollen, densely spinose end cells (acanthohyphidia); this species has never been observed fertile. The common Cora glabrata is foliose, forming large, radially zonate, conch-like, often tiled thalli, when fertile with circular lines of basidiocarps on its lower side. Dictyonema is distinguished by filamentous cyanobionts and distinctly filamentous thalli that are homomereous (i.e., not distinctly layered); all species of Dictyonema s.str. have trichomes (filamentose cyanobacterial photobionts) closely enveloped by fungal cells of a jigsaw pattern. In D. sericeum thallus filaments (i.e., individual fibrils) aggregate to form shelf-like structures similar in appearance to polyporoid bracket fungi; basidiocarps develop in irregular patches on the lower side of these shelves. In contrast, fibrils of D. schenkianum grow encrusting their substrate with irregularly to suberect trichomes, occasionally bearing basidiocarps dispersed across the thallus. Two other species in Galapagos show adpressed growth form and are described here as new: Dictyonema pectinatum, which is characterized by large parallel fibrils with paler, papillate tips, and D. galapagoense, characterized by thin trichomes of more squarrish elongate cells. The genus Cyphellostereum is represented by two species: the newly described C. imperfectum and an unnamed Cyphellostereum sp., both phenotypically similar to free-living cyanobacterial filaments. Cyphellostereum imperfectum has narrow photobiont filaments with irregular hyphal sheath leaving interspaces; macroscopically it shows a bluish green thallus with a distinct prothallus. Cyphellostereum sp. has a rather uncommon basidiolichen appearance: thin sctytonematoid fibrils surrounded by straight fungal cells forming shiny tufts. The new combination Cyphellostereum nitidum is also proposed. The ecology and taxonomy of Galapagos basidiolichens is briefly discussed and a key and short descriptions of all species are presented.

Porphyra migitae sp. nov. (Bangiales, Rhodophyta) from Japan

Kikuchi N., Arai S., Yoshida G., Shin J.-A., Broom J.E., Nelson W.A. and Miyata M. 2010. Porphyra migitae sp. nov. (Bangiales, Rhodophyta) from Japan. Phycologia 49: 345–354. DOI: 10.2216/09-82.1A new species of Porphyra, Porphyra migitae sp. nov., coloured fire red and collected subtidally in two localities in Japan, is described based on morphology, life history and molecular analyses. The new species can be distinguished from other fire-red coloured Porphyra species by a range of characters including the presence of conchospores and many archeospores and neutral spores on foliose thalli. Foliose thalli, which are sometimes lobed, are monoecious, and clearly distinguishable patches of spermatangial sori are not formed. Many holes are formed on the foliose thalli after release of spermatia. This species has a heteromorphic life history in which the macroscopic gametophytic foliose thalli alternate with the microscopic sporophytic filamentous thalli (conchocelis). In addition, the life history includes additional reproductive cycles of the foliose thalli via archeospores and neutral spores. This species has the widest range of asexual reproductive strategies so far observed in the Bangiales. Molecular phylogenies based on both the nuclear SSU rDNA and the rbcL genes enable this species to be distinguished from other species of Porphyra for which there are equivalent data.

CLONING AND QUANTITATIVE ANALYSIS OF THE CARBONIC ANHYDRASE GENE FROMPORPHYRA YEZOENSIS

Carbonic anhydrase (CA), an enzyme that catalyzes the interconversion of CO2 and HCO3−, has a critical role in inorganic carbon acquisition in many kingdoms, including animals, plants, and bacteria. In this study, the full-length cDNA of the CA gene from Porphyra yezoensis Ueda (denoted as PyCA) was cloned by using an expressed sequence tag (EST) and rapid amplification of cDNA ends (RACE). The nucleotide sequence of PyCA consists of 1,153 bp, including a 5′ untranslated region (UTR) of 177 bp, a 3′ UTR of 151 bp, and an open reading frame (ORF) of 825 bp that can be translated into a 274-amino-acid putative peptide with a molecular mass (M) of 29.8 kDa and putative isoelectric point (pI) of 8.51. The predicted polypeptide has significant homology to the β-CA from bacteria and unicellular algae, such as Porphyridium purpureum. The mRNA in filamentous thalli, leafy thalli, and conchospores was examined, respectively, by real-time fluorescent quantitative PCR (qPCR), and the levels of PyCA are different at different stages of the life cycle. The lowest level of mRNA was observed in leafy thalli, and the level in filamentous thalli and in the conchospores was 4-fold higher and 10-fold higher, respectively.

EPIPHYTIC FORAMINIFERAL ASSEMBLAGES ON MACROALGAE IN REEFAL ENVIRONMENTS OF NEW CALEDONIA

Research Article| January 01, 2010 EPIPHYTIC FORAMINIFERAL ASSEMBLAGES ON MACROALGAE IN REEFAL ENVIRONMENTS OF NEW CALEDONIA Jean-Pierre Debenay; Jean-Pierre Debenay 4 1IRD, UR 055 “Paléotropique”, 101 promenade Roger Laroque, BP A5, 98848 Nouméa cedex, Nouvelle-Calédonie 3Current address: 430 Chemin de Montplaisir 34190 Laroque, France 4Correspondence author. E-mail: debenay@wanadoo.fr Search for other works by this author on: GSW Google Scholar Claude E. Payri Claude E. Payri 2IRD, UMR 7138/UR R148 “Systématique, Adaptation, Evolution”, 101 promenade Roger Laroque, BP A5, 98848 Nouméa cedex, Nouvelle-Calédonie Search for other works by this author on: GSW Google Scholar Journal of Foraminiferal Research (2010) 40 (1): 36–60. https://doi.org/10.2113/gsjfr.40.1.36 Article history received: 23 Nov 2008 accepted: 16 Jul 2009 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Jean-Pierre Debenay, Claude E. Payri; EPIPHYTIC FORAMINIFERAL ASSEMBLAGES ON MACROALGAE IN REEFAL ENVIRONMENTS OF NEW CALEDONIA. Journal of Foraminiferal Research 2010;; 40 (1): 36–60. doi: https://doi.org/10.2113/gsjfr.40.1.36 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyJournal of Foraminiferal Research Search Advanced Search Abstract Modern epiphytic foraminifera have been reported on seagrasses from different areas, but little is known about those living on macroalgae. This study on reefal environments of New Caledonia is the first to inventory epiphytic foraminifera on a large number of well-identified macroalgae. Its objective is to learn more about epiphytal foraminiferal ecology and its use for environmental and paleoenvironmental interpretations. A total of 152 species of epiphytic foraminifera were identified on 81 substratal phyta that include 55 species of macroalgae. This study confirms the complexity of the distribution of foraminiferal communities on phytal substrata at a micro-scale, and shows that temporal availability of the substratum might play a role. It also reveals that some foraminiferal species might have quite different life modes between environments and regions. The structural characteristics of the macroalgae explain part of the differences in epiphytic foraminiferal assemblage composition. The only strong relationship established between macroalgae and foraminifera is the presence of spinose rotaliids, soritids, and Amphistegina in filamentous thalli and three-dimensional mats. However, macroalgal species that have a wide bathymetric range might harbor completely different communities at different depths, in which case the nature of the substratum might be overshadowed by other parameters such as light, depth, and hydrodynamics. These results call for prudence when interpreting paleoenvironmental data, and show that long-term monitoring is needed to define population dynamics that could be applied in paleoenvironment and paleoclimate reconstructions. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Streptophyte algae and the origin of embryophytes

Land plants (embryophytes) evolved from streptophyte green algae, a small group of freshwater algae ranging from scaly, unicellular flagellates (Mesostigma) to complex, filamentous thalli with branching, cell differentiation and apical growth (Charales). Streptophyte algae and embryophytes form the division Streptophyta, whereas the remaining green algae are classified as Chlorophyta. The Charales (stoneworts) are often considered to be sister to land plants, suggesting progressive evolution towards cellular complexity within streptophyte green algae. Many cellular (e.g. phragmoplast, plasmodesmata, hexameric cellulose synthase, structure of flagellated cells, oogamous sexual reproduction with zygote retention) and physiological characters (e.g. type of photorespiration, phytochrome system) originated within streptophyte algae. Phylogenetic studies have demonstrated that Mesostigma (flagellate) and Chlorokybus (sarcinoid) form the earliest divergence within streptophytes, as sister to all other Streptophyta including embryophytes. The question whether Charales, Coleochaetales or Zygnematales are the sister to embryophytes is still (or, again) hotly debated. Projects to study genome evolution within streptophytes including protein families and polyadenylation signals have been initiated. In agreement with morphological and physiological features, many molecular traits believed to be specific for embryophytes have been shown to predate the Chlorophyta/Streptophyta split, or to have originated within streptophyte algae. Molecular phylogenies and the fossil record allow a detailed reconstruction of the early evolutionary events that led to the origin of true land plants, and shaped the current diversity and ecology of streptophyte green algae and their embryophyte descendants. The Streptophyta/Chlorophyta divergence correlates with a remarkably conservative preference for freshwater/marine habitats, and the early freshwater adaptation of streptophyte algae was a major advantage for the earliest land plants, even before the origin of the embryo and the sporophyte generation. The complete genomes of a few key streptophyte algae taxa will be required for a better understanding of the colonization of terrestrial habitats by streptophytes.

MOLECULAR PHYLOGENY OF DISCOSPORANGIUM MESARTHROCARPUM (PHAEOPHYCEAE) WITH A REINSTATEMENT OF THE ORDER DISCOSPORANGIALES1

A molecular phylogenetic analysis of the little‐studied filamentous brown alga Discosporangium mesarthrocarpum (Meneghini) Hauck using rbcL and partial 18S rDNA sequences revealed that the species forms a monophyletic clade with Choristocarpus tenellus (Kütz.) Zanardini that is sister to all other brown algae. Although D. mesarthrocarpum has unique disk‐shaped plurilocular reproductive organs, D. mesarthrocarpum and C. tenellus share the following basic morphological features, which are considered to be plesiomorphic characters in the brown algae: (1) apical (and diffuse) growth; (2) uniseriate, subdichotomously branched filaments; (3) multiple chloroplasts per cell without pyrenoids; and (4) lack of heterotrichy and of phaeophycean hairs. The rbcL DNA sequence of an Australian D. mesarthrocarpum specimen showed considerable deviation from Mediterranean and Macaronesian specimens. Therefore, the presence of a second species in the genus is suggested; however, the taxonomic treatment of this putative species is not pursued in the present report. Regarding the higher‐ranking systematic position of D. mesarthrocarpum, reinstatement of Discosporangiaceae and Discosporangiales is proposed, and the inclusion of Choristocarpaceae in the order is also suggested. Under short‐day and long‐day culture conditions at 15°C–25°C, Mediterranean D. mesarthrocarpum exhibited a direct type of life history, with a succession of uniseriate filamentous thalli bearing characteristic disk‐shaped plurilocular zoidangia, but thalli did not survive at 10°C and below.

Relative contribution of vegetative propagation and sexual reproduction in the maintenance of Acrosiphonia (Chlorophyta) populations

A.V. Sussmann and R.E. Dewreede. 2007. Relative contribution of vegetative propagation and sexual reproduction in the maintenance of Acrosiphonia (Chlorophyta) populations. Phycologia 46: 79–85. DOI: 10.2216/06-33.1We provide evidence for new vegetative growth in spring from overwintering basal remnants of the green alga Acrosiphonia (Codiolales sensu van den Hoek et al. 1995) long after mortality of the filamentous thalli at two independent study sites in Barkley Sound, British Columbia, Canada. The two study sites differed in Acrosiphonia species composition, abundance and seasonality, but were both characterised by disturbance. At Prasiola Point we estimated approximately 15–30% Acrosiphonia recruitment to originate from vegetative regrowth (based on mapping individual thalli). At Seppings Island significantly lower Acrosiphonia recruitment on cleared boulders than uncleared boulders provided an estimate of approximately 50% recruitment from vegetative regrowth. These results increase our understanding of the complex life history of Acrosiphonia in southwestern British Columbia by detecting the role of vegetative propagation in the maintenance of sexually reproducing populations. The previously undocumented capacity to regenerate in the field by vegetative means also explains the seasonally dense occurrence of the gametophyte phase and Acrosiphonia's success in colonising disturbed environments. In conditions of limited zoospore availability, dispersal and attachment it is advantageous for populations to regenerate vegetatively.