1,139 publications found
Sort by
Molecular study of the rare genus <scp><i>Neoabbottiella</i></scp> (Rhodophyta) reveals its assignment to the Halymeniaceae is incorrect

SUMMARYThe rare red algal genus Neoabbottiella from the Russian Pacific coast was taxonomically re‐examined. Currently, Neoabbottiella is assigned to the Halymeniales; however, some features of the reproductive anatomy cast doubt on the correctness of assigning the genus to Halymeniaceae sensu lato. We investigated the phylogenetic affinities of Neoabbottiella using four DNA markers (nuclear LSU and SSU rDNA, rbcL and COI‐5P). Neoabbottiella failed to group with any families of the Halymeniales, but it was nested in a highly supported clade containing representatives of the genus Schmitzia (Calosiphoniaceae incertae sedis). Reproductive anatomy and post‐fertilization development also separate Neoabbottiella from the Halymeniaceae. The main characteristics distinguishing Neoabbottiella from the Halymeniales include the intercalary position of the auxiliary cell, the contact of the connecting filament with the auxiliary cell via the lateral process, the origin of the initial gonimoblast cell from the connecting filament at a distance from the auxiliary cell and a lack of a pericarp of branched ampullar filaments. These traits bring Neoabbottiella close to its genetic sister genus Schmitzia, making the classification of Neoabbottiella at the family and order levels difficult. The eventual taxonomic classification of Neoabbottiella awaits the input of data of other species of Schmitzia as well as Calosiphonia, the type genus of the Calosiphoniaceae; thus, Neoabbottiella should be provisionally excluded from the Halymeniales and considered as incertae sedis in the Rhodymeniophycidae. Further, the results of the present study showed that Neoabbottiella is monotypic; Neoabbottiella decipiens should be recognized as a synonym of the generitype Neoabbottiella araneosa.

Characterization of cell wall polysaccharide from <scp><i>Cladosiphon okamuranus</i></scp> cultivated in different locations

SUMMARYCladosiphon okamuranus is an excellent source of fucoidan among any brown algae spp. However, the structure of polysaccharide varies significantly depending on the species, harvesting season and geographical location. To understand how geographic location affects the structure of cell wall polysaccharide, C. okamuranus cultivated in eight places (Bise, Katsuren, Yonashiro, Shikiya, Karimata, Nishihara, Hisamatsu and Ishigaki) in Ryukyu archipelago were collected during the peak harvesting time and the cell wall polysaccharide was analyzed physiochemically. The cell wall was sequentially fractionated into five fractions and its 80% was consisted of hot water fraction (HW) (60–70%) and hemicellulose‐I fraction (HC‐I) (15–20%), which mainly contained fucoidan composed of fucose (Fuc), glucuronic acid (GlcA) and sulfate (SO3−). Although the chemical composition and molecular weight of fucoidan in HW was slightly different at different places, the composition of Fuc, GlcA and SO3− was constant in the molar ratio of 1.0:0.5:0.7–1.0 respectively, suggesting that relatively similar structural fucoidan from C. okamuranus can be obtained from any geographical location in Okinawa Prefecture during peak time. However, considerable variation in the sugar composition in HC‐I was observed, despite the uniform molecular weight and SO3−. Particularly, HC‐I from Bise, where is the northern part of Okinawa Island, is composed of significantly higher amounts of Glc, Gal, Man, Xyl and morphologically thicker lateral branches compared to algae from the other parts of the island.

Composition of galactolipids, betaine lipids and triglyceride‐associated fatty acids of the symbiotic dinoflagellate <scp><i>Zooxanthella</i></scp> (<i>Brandtodinium</i>) <i>nutricula</i>: A glimpse into polyunsaturated fatty acids available to its polycystine radiolarian host

SUMMARYZooxanthella nutricula is a photosynthetic dinoflagellate symbiont of polycystine radiolarians. As such, it is hypothesized to provide fixed organic carbon, including in the form of acylglycerolipids and sterols, to its non‐photosynthetic host. We have previously characterized the sterols of Z. nutricula that may be transferred to its host and, in the present study, have turned our attention to three classes of fatty acid‐containing lipids, chloroplast‐associated galactolipids, betaine lipids, which are non‐phosphorylated phospholipid analogs present in many eukaryotes, and triglycerides. Zooxanthella nutricula was observed using positive‐ion electrospray/mass spectrometry (ESI/MS) and ESI/MS/MS to produce the galactolipids mono‐ and digalactosyldiacylglycerol (MGDG and DGDG, respectively) enriched in octadecapentaenoic (18:5(n‐3)) and octadecatetraenoic (18:4(n‐3)) acid to place it within a group of peridinin‐containing dinoflagellates in a C18/C18 (sn‐1/sn‐2 fatty acid regiochemistry) cluster, as opposed to another cluster with C20/C18 MGDG and DGDG, where the C20 fatty acid is eicosapentaenoic acid (20:5(n‐3)) and the C18 fatty acid is either 18:5(n‐3) or 18:4(n‐3). Zooxanthella nutricula was also observed to produce 38:10 (total number of fatty acid carbons:total number of double bonds), 38:6, and 44:7 diacylglycerylcarboxyhydroxymethylcholine (DGCC) as the sole type of betaine lipid. Although it is more difficult to determine which fatty acids are present in the sn‐1 and sn‐2 positions on the glycerol backbone of DGCC using ESI/MS/MS, gas chromatography/mass spectrometry (GC/MS)‐based examination indicated the putatively DGCC‐associated polyunsaturated fatty acid (PUFA) docosahexaenoic acid (22:6(n‐3)). Coupled with the C18 PUFAs of MGDG and DGDG, and fatty acids associated with triglycerides (also examined via GC/MS), Z. nutricula could serve as a rich source of PUFAs for its radiolarian host. These data demonstrate that Z. nutricula produces a similar set of PUFA‐containing lipids as Symbiodinium microadriaticum, a photosynthetic dinoflagellate symbiont of cnidarians, indicating a metabolic commonality in these phylogenetically discrete dinoflagellate symbionts with unrelated host organisms.

Open Access
Betaine lipids of Symbiodiniaceae hosted by Indo‐Pacific corals

SUMMARYThe total pool of coral lipids consists of lipids produced by both the coral host and its symbiotic dinoflagellates of the family Symbiodiniaceae. Betaine lipids (BL) are characteristic of plasma membranes of microalgae. Composition of such BL as 1,2‐diacylglyceryl‐3‐O‐carboxy‐(hydroxymethyl)‐choline (DGCC) that occur in coral symbionts may depend on either Symbiodiniaceae species or coral species. Membrane‐forming lipids DGCC have a zwitterion structure similar to that of phosphatidylcholine (PC). They can substitute for each other to a substantial extent, certainly in relation to membrane functions. In the present study, the profiles of DGCC and diacyl PC molecular species of symbiotic dinoflagellates from Acropora sp., Millepora platyphylla and Sinularia flexibilis were determined by high‐performance liquid chromatography with high‐resolution mass‐spectrometry. Colonies of Acropora sp. were characterized by higher contents of DGCC with eicosapentaenoic acid (20:5n‐3) and C28 polyunsaturated fatty acids; S. flexibilis, by a higher content of DGCC with palmitic acid (16:0); and M. platyphylla, by a higher content of DGCC with docosahexaenoic acid (22:6n‐3). Although the DGCC profile of the corals under study has distinctive features, it shows both similarities with and differences from the DGCC profiles of previously studied corals. Probably, each coral symbiont species has its own specific DGCC molecular species profile that is additionally modified in a certain way depending on environmental conditions created by the coral host. Molecular species DGCC and PC profiles were different. The most abundant PC molecular species were 16:0/22:5 and 38:4 in Acropora sp.; 39:5 and 38:4 in S. flexibilis; and 38:6, 16:0/22:5 and 18:0/22:6 in M. platyphylla. Thus, there is no clear evidence for any compensation or interchangeability between PC and DGCC.

Confirmation of <i>Neoporphyra</i> cf. <i>dentata</i> on <scp>Shikinejima</scp>, <scp>Izu Islands</scp>, southcentral <scp>Japan</scp>, and comparison with co‐occurring <i>Neoporphyra haitanensis</i>

SUMMARYThe Izu Islands of southcentral Japan are thought to fall within the distribution range of Neoporphyra dentata. However, the gametophytic blades of Bangiales collected from Shikinejima and Hachijojima, Izu Islands, were identified as Neoporphyra haitanensis in our previous study. Thus, it became uncertain whether N. dentata is distributed in the Izu Islands, including Shikinejima. To clarify whether N. dentata grows on Shikinejima, we conducted a further distribution survey of N. dentata on the island. The morphological features of the blade samples collected from an additional sampling site on Shikinejima were more similar to those of N. dentata than to those of N. haitanensis: the blade thickness and the division formula of spermatangia resembled those of the former species rather than the latter species. However, the division formula of zygotosporangia was different from those of either species. The phylogenetic analyses of the rbcL gene indicated that the samples were resolved in a clade including N. dentata collected from Shirahama, Chiba Prefecture, and Enoshima, Kanagawa Prefecture, Honshu, Japan. The p‐distances of the chloroplast rbcL gene and nuclear 18S rRNA also supported identification of the samples as N. dentata. The results demonstrated that N. dentata is also distributed on Shikinejima with co‐occurring N. haitanensis, and that the island materials of the two species are genetically different from other materials of the two species, respectively.

Morphology and molecular phylogeny of the marine diatom genus <i>Nagumoea</i> (<scp>Bacillariophyceae</scp>) from <scp>Japan</scp>

SUMMARYThe canal‐bearing diatom genus Nagumoea, described based on only morphological evidence, was tentatively assigned to the order Bacillariales, although its phylogenetic position remained unclear. Because three isolates of Nagumoea (SK002, SK024 and SK053) were successfully established from Japanese coasts, we performed their morphological observations and molecular phylogenetic analyses to discuss the phylogeny and taxonomic position of this genus. Strains SK002 and SK024 were identified as Nagumoea africana, whereas SK053 conformed with Nagumoea serrata. There was high interspecific divergence between N. africana and N. serrata in the rbcL sequences (8.03–8.17%), indicating their distinctness. Furthermore, intraspecific variations were detected within N. africana (2.35%) in the rbcL, implying its cryptic diversity. The maximum likelihood and Bayesian phylogenetic trees inferred from the plastid rbcL, psbC and nuclear 18S rDNA genes recovered Nagumoea as monophyletic with strong statistical support and embedded within an unresolved, poorly supported lineage containing Achnanthes, Craspedostauros, Staurotropis and Undatella in the canal‐bearing order Bacillariales (= the family Bacillariaceae). Although the constrained tree based on the monophyly of Nagumoea and the other canal‐bearing clade (Surirellales and Rhopalodiales) was statistically rejected by the topology tests, the phylogenetic position of Nagumoea with other Bacillarialean members remains equivocal. The possession of two plastids positioned fore and aft, observed in the present study, and lack of keel, typical of the Bacillariales, indicate the possibility of Nagumoea being part of the ingroup of the Bacillariales or its closely related outgroup.