Search

Mineral phase analysis was performed, using X-ray diffractometry (XRD), for marine-organism shell/skeleton samples of 146–148 extant species of the following 10 phyla (18 classes) collected in Japan: Rhodophyta (Florideophyceae), Foraminifera (Globothalamea and Tubothalamea), Porifera (Hexactinellida), Cnidaria (Anthozoa and Hydrozoa), Bryozoa (Gymnolaemata), Brachiopoda (Lingulata and Rhynchonellata), Mollusca (Bivalvia, Cephalopoda, Gastropoda and Polyplacophora), Annelida (Polychaeta), Arthropoda (Cirripedia), and Echinodermata (Asteroidea, Crinoidea and Echinoidea). Some of the species were analyzed for each specific part of their shells/skeletons. Almost all the samples exhibited any of calcite, aragonite or their mixed phase, predominantly depending on their taxonomy and shell/skeletal structures. For samples containing significant amounts of calcite, the MgCO3wt % of calcite has been determined from their XRD data, which ranges from ∼0 to ∼15 wt % and indicates clear inter-taxonomic differences. Low MgCO3values (∼0–4 wt %) are observed for Rhynchonellata, Bivalvia, Gastropoda and Cirripedia; intermediate values (∼4–8 wt %) for Cephalopoda; high values (∼8–15 wt %) for Florideophyceae, Globothalamea, Tubothalamea, Polychaeta, Asteroidea and Crinoidea; low-to-high values for Gymnolaemata; intermediate-to-high values for Anthozoa and Echinoidea. These MgCO3data show broad trends mostly consistent with general phylogenetic evolution (i.e. very similar patterns for each phylogenetic group). Distinct within-individual variability of the MgCO3content is found for regular Echinoidea species (i.e. their teeth and spines have lower MgCO3values than the other skeletal parts). Correlation of the MgCO3content with seawater temperature is also examined/discussed for most of the above calcite-containing classes. In order to interpret our XRD-based observations of various marine-species shells/skeletons, detailed discussions are presented by comparing with previous studies and also by using knowledge of taxonomy, shell/skeletal structures, habitats, living modes and so on. The comprehensive dataset and discussions will provide useful implications for biomineralization studies.

The brown alga Scytosiphon lomentaria (Scytosiphonaceae, Ectocarpales) has been reported from cold and warm waters worldwide. Although previous molecular phylogenetic studies and crossing experiments have shown that it is a complex of multiple distinct species, the taxonomic position and accurate distribution of each species have remained largely unclear. For the S. lomentaria complex from Japan, our cox1 and rbcL phylogenetic analyses detected six species. In addition to five previously detected species (species Ia-Va), one species (species VI) was newly found in the subtropical area, Okinawa Island. Species VI was recovered as a sister to species Ia-Va in rbcL. Based on the morphological and phylogenetic data, we concluded that species Ia is S. lomentaria, species IIIa is S. promiscuus, and the other four species are newly described: S. shibazakiorum for species IIa, S. tosaensis for species IVa, S. arcanus for species Va, and S. subtropicus for species VI. The cox1-based analysis also showed that S. lomentaria, S. shibazakiorum, and S. promiscuus have worldwide distributions, while the other three species were not found outside of Japan. In Japan, except for S. subtropicus, distributions of these species overlapped. Our crossing experiments showed that gametic incompatibility (pre-zygotic barrier) was less developed between the allopatric species (i.e., S. subtropicus and others) compared with the sympatric species. It may suggest that pre-zygotic barriers have evolved among the sympatric species due to reinforcement.

This datasheet on Ulva ohnoi covers Identity, Overview, Distribution, Dispersal, Diagnosis, Biology & Ecology, Environmental Requirements, Natural Enemies, Impacts, Uses, Further Information.

The green seaweed Ulva spp. constitute major primary producers in marine coastal ecosystems. Some Ulva populations have declined in response to ocean warming, whereas others cause massive blooms as a floating form of large thalli mostly composed of uniform somatic cells even under high temperature conditions—a phenomenon called “green tide”. Such differences in population responses can be attributed to the fate of cells between alternative courses, somatic cell division (vegetative growth), and sporic cell division (spore production). In the present review, I attempt to link natural population dynamics to the findings of physiological in vitro research. Consequently, it is elucidated that the inhibition of biomass allocation to sporulation is an important key property for Ulva to cause a huge green tide.

Tosa Bay in southwestern Japan is experiencing dramatic community phase shifts where temperate seaweed beds of brown algae have been tropicalized, a trend that has coincided with the most significant increases in surface seawater temperature in the world. Here, we report that blooms of green seaweed (genus Ulva) are also undergoing species replacement in this region, coincident with the tropicalization. Ulva green tides have been reported in Uranouchi Inlet, central Tosa Bay, since the late 1970s. The causative species was described as a new species, Ulva ohnoi, in 2004. However, the present investigation using a DNA marker-based identification technique showed that U. ohnoi did not form blooms but sparsely produced thallus fragments in the inlet during the period 2017–2018. Instead, the cosmopolitan species Ulva reticulata which has a distribution centered in more tropical waters was repeatedly found to dominate and form dense drifts in the inner end of the inlet.

Ulva is a green macroalga often causing a macroalgal bloom, ‘green tide’. Ulva ohnoi is a major species composing the green tide of the southern coastal regions of Japan. Here, we sequenced the complete mitochondrial and chloroplast genomes of the authentic strain of U. ohnoi. The mitochondrial and chloroplast genomes were of 65,326 bp and 103,313 bp, respectively, and the gene content was highly conserved in the Ulva species. The phylogenetic analyses using mitochondrial or chloroplast proteins represented the same topology with high supporting values. These results show that mitochondrial and chloroplast genomes can be used as reliable phylogenetic markers.

The high growth rate of Ulva seaweeds makes it a potential algal biomass resource. In particular, Ulva meridionalis grows up to fourfold a day. Here, we demonstrated strong carbon fixation by U. meridionalis using 13C stable isotope labelling and traced the 13C flux through sugar metabolites with isotope-ratio mass spectrometry (IR-MS), Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), 13C-nuclear magnetic resonance spectrometry (13C-NMR), and gas chromatography-mass spectrometry (GC–MS). U. meridionalis was first cultured in 13C-labelled enriched artificial seawater for 0–12 h, and the algae were collected every 4 h. U. meridionalis grew 1.8-fold (dry weight), and the 13C ratio reached 40% in 12 h, whereas 13C incorporation hardly occurred under darkness. At the beginning of the light period, 13C was incorporated into nucleic diphosphate (NDP) sugars in 4 h, and 13C labelled peaks were identified using FT-ICR-MS spectra. Using semiquantitative 13C-NMR measurements and GC–MS, 13C was detected in starch and matrix polysaccharides after the formation of NDP sugars. Moreover, the 14:10 light:dark regime resulted into 85% of 13C labelling was achieved after 72 h of cultivation. The rapid 13C uptake by U. meridionalis shows its strong carbon fixation capacity as a promising seaweed biomass feedstock.

Microalgae with high growth rates have been considered as promising organisms to replace fossil resources with contemporary primary production as a renewable source. However, their microscopic size makes it hard to be harvested for industrial applications. In this regard, multicellular macroalgae are more suitable for harvesting. Here, we show that Ulva meridionalis has the highest growth rate ever reported for a multicellular autotrophic plant. Contrasted to the known bloom-forming species U. prolifera growing at an approximately two-fold growth rate per day in optimum conditions, U. meridionalis grows at a daily rate of over fourfold. The high growth ability of this multicellular alga would provide the most effective method for CO2 fixation and biomass production.

Thallusin is the only known natural product that induces cell differentiation followed by formation of a thallus during the growth of green macroalgae such as Monostroma and Ulva . Herein, various thallusin analogues based on the terpen skeleton were synthesized to study the structure−activity relationships of thallusin. The potency of the synthetic analogues was investigated in an experimental assay, which demonstrated that the 19-methyl group in thallusin is essential for potent morphogenesis-inducing activity.

Since 2008, the green seaweed Ulva prolifera has caused the world's largest green tide in the Yellow Sea, China. It has subsequently attracted considerable research interest. However, species identification is an essential step for advancing this research. Based on phylogenetic analyses using molecular sequences such as internal transcribed spacer (ITS) or ribulose bisphosphate carboxylase large chain (rbcL), specimens of U. prolifera collected worldwide were separated into a European clade and the Ulva linza–procera–prolifera (LPP) complex clade that included the Chinese bloom-forming strains and Japanese brackish strains. This has resulted in considerable controversy as to the identity of U. prolifera and the bloom-forming species in the Yellow Sea. To resolve this issue, we examined populations of U. prolifera from the type locality at Lolland Island, Denmark, and globally significant sites including sites from Japan and China using morphological, developmental, molecular and crossing studies....

Phylogenetic clades based on DNA sequences such as the chloroplast rbcL gene and the nuclear ITS region are frequently used to delimit algal species. However, these molecular markers cannot accurately delimit boundaries among some Ulva species. Although Ulva reticulata and Ulva ohnoi occasionally bloom in tropical to warm-temperate regions and are clearly distinguishable by their reticulate or plain blade morphology, they have few or no sequence divergences in these molecular markers and form a monophyletic clade. In this study, to clarify the speciation and species delimitation in the U. reticulata-ohnoi complex clade, reproductive relationships among several sexual strains from the Philippines and Japan including offspring that originated from the type specimen of U. ohnoi were examined by culturing and hybridization in addition to the ITS-based analysis. As a result, both prezygotic and postzygotic reproductive isolation were revealed to occur between genetically perforated U. reticulata and imperforate U. ohnoi. They were also separated on the basis of sequence analysis of the ITS region. That strongly supports that the two taxa are independent biological species. Although no prezygotic barrier among the Philippine and Japanese strains of U. reticulata was observed, unexpectedly zoospores produced by hybrid sporophytes in some of their combinations mostly failed to develop, indicating partial formation of a postzygotic barrier despite a 0.2% divergence in the ITS sequence. These findings suggest speciation is still ongoing in U. reticulata.

Phylogenetic clades based on DNA sequence data are heavily used to delimit species in the current taxonomy of Ulva. However, because hybridisation within clades and among other clades for other species has been seldom tested, it remains unclear if molecular clades agree with species boundaries based on the biological species concept. An ITS-based Ulva clade including many specimens collected worldwide was provisionally named ‘U. flexuosa'; its species boundary is ambiguous, and in the literature this group has been variously merged with the closely related U. californica clade. In the present study, we clarified the species boundary of this clade and its taxonomic status. Namely reproductive relationships among strains in this and closely related clades were examined by culturing and hybridisation. The culture experiment demonstrated that the ITS-based clade includes a sexual variant and an obligate asexual variant. The sexual strains having 0%–0.4% divergence in ITS2 sequence successfully cross...

Activated carbon supported polyoxometalates (AC-POMs) were used for acceleration of hydrolysis of biomass under microwave irradiation. Microwaves exhibited a higher saccharification rate for cellobiose and green seaweed (Monostroma latissimum) over AC-POMs than conductive heating by 1.25 to 1.55-fold. The activity of the AC-POMs was positively correlated with the dielectric loss of the catalysts, suggesting that microwave susceptibility of AC-POMs is relevant to the enhancement of catalysis under microwave irradiation.

Microwave-assisted hydrothermal extraction was applied for production of sulfated polysaccharides from Ulva spp. and Monostroma latissimum . The maximum ulvan yields attained 40.4 ± 3.2% ( Ulva meridionalis ) and 36.5 ± 3.1% ( Ulva ohnoi ) within 4 min of come-up time and 10 min of extraction time at 160 °C, respectively. The rhamnan sulfate yield from M . latissimum further attained 53.1 ± 7.2% at 140 °C. The sulfated polysaccharides were easily recovered from the extract by simple ethanol precipitation. In addition, molecular weights and viscosity of the extracted polysaccharides could be controlled by varying the extraction temperature. Dielectric measurement revealed that ionic conduction was the important parameter that affect the microwave susceptibility of algae-water mixture. The sulfated polysaccharides extracts are expected as potential feedstock for medical and food applications.

Where sexual and asexual forms coexist within a species, the asexuals are often found to be prevalent in marginal habitats. This asexual distribution pattern has received evolutionary attention linked to the paradox of sex. In many marine species, there is a distributional trend of asexual modes being more common in lower salinity waters regarded as the ecogeographic marginal, being explained by negative effects of low salinities on sexual reproductive success. However, the distribution pattern of estuarine species recently adapted to low salinity waters has remained unknown. The brackish macroalga Ulva prolifera being a major benthic component of estuarine ecosystems includes a sexual variant and obligate asexual variants by means of motile spores. We examined the sexual-asexual distribution pattern of this alga along a salinity gradient in river estuaries. Surprisingly, opposite to the distributional trend of marine organisms, the results clearly showed the persistent predominance of sexuals in the lower salinity reaches than the asexuals. In addition, a frequent alternating of dioecious gametophytes and sporophytes in the sexual population was observed, suggesting the sexual reproductive process would be robustly performed in the low salinity waters. Considering U. prolifera had evolved from the ancestral marine species to become a true estuarine species of which the core habitat is the low salinity reaches, in a broad sense its sexual-asexual distribution pattern would be involved in asexual marginal occupations of the species range previously reported in other organisms. Based on the frozen niche variation model, we can give a concise explanation for the evolutionary process of this pattern; multiple asexuals with frozen genotypic variation had arisen from sexual ancestors undergoing low salinity adaptation and share the estuarine habitat with the sexuals at present.

Since the late 1980’s, a persistent green tide of floating Ulva without any clear seasonal fluctuation has occurred in Hiroshima Bay, Seto Inland Sea, Japan. We hypothesized that the persistence is due to the co-existence of Ulva species with different seasonal growth patterns, and monitored the seasonal composition and growth characteristics of the constituent Ulva within the green tide. Two morphological types of Ulva were identified, and one type, U. pertusa, was almost the sole constituent during winter and spring. The other type Ulva spp., which has marginal microscopic serrations on the thallus, was dominant during summer and autumn. Both Ulva showed the highest relative growth rate in early autumn, but growth of Ulva spp. was faster in summer than that of U. pertusa and inhibited in winter. U. pertusa had more eurythermal characteristics in which the growth rate remained relatively high in winter. Water temperature was the most correlated environmental variable for the seasonal growth of both Ulva types rather than light or nutrients, but more influential on Ulva spp. Recent increasing trend of ambient seawater temperature is considered to be favorable for the growth of both Ulva types and a causative factor of the green tide.

This study investigated the dielectric properties of sodium alginates and carrageenans in water at frequencies between 100 MHz and 20 GHz in regard to water-hydrocolloid interactions via acidic functional groups. Both sodium alginates and carrageenans showed conduction loss at lower frequencies and dielectric loss at higher frequencies. Reduction and desulfation of sodium alginates and carrageenans, which decreased the numbers of acidic functional groups, decreased their conduction loss. In addition, H+-form carrageenans showed the highest ionic conduction. Correlational analysis of dielectric properties and related physical parameters showed that the loss tangent (tanδ) of the hydrocolloid solution was determined by the conductivity of the aqueous solution. Especially at pH below 2, strong H+ conduction was associated with high tanδ probably due to the Grotthuss mechanism. The molecular dynamics of free water and H+, viscosity conditions were also suggested to be associated with dielectric property of water-hydrocolloid system.

Microwaves provide rapid and efficient water extraction of carbohydrates because microwaves directly generate heat by dipole rotations of water molecules. Microwaves penetrate into biomass substrates and generate heat from within, thus enhancing the extraction efficiency of the components contained in the plant bodies. In addition, water under high temperature and pressurized condition enables extraction and autohydorolysis of polysaccharides without using hazardous chemicals. This chapter, therefore, summarizes fundamentals and applications of water extraction of carbohydrates from unutilized biomass (agricultural wastes, food wastes and seaweeds) using microwaves under hydrothermal condition. The dielectric properties relevant for water extraction of polysaccharides are also discussed to understand the heating mechanism of the mixture of water and biomass.

This chapter focuses on the effects of microwave on hydrothermal processing of algal biomass, especially fast-growing green seaweed biomass of Ulva. Microwave enhances the efficiency of hydrothermal treatment of biomass by directly affecting water molecule, catalysts, and biomass substrates. Firstly, the fundamentals of microwave-assisted biorefinery are illustrated. Then, the microwave effects for hydrothermal processing of biomass were summarized for the model sugar reaction and seaweed conversion. Dielectric properties of seaweed biomass relevant to microwave heating are also presented in the last section.

To assess distributional shifts of species in response to recent warming, historical distribution records are the most requisite information. The surface seawater temperature (SST) of Kochi Prefecture, southwestern Japan on the western North Pacific, has significantly risen, being warmed by the Kuroshio Current. Past distributional records of subtidal canopy-forming seaweeds (Laminariales and Fucales) exist at about 10-year intervals from the 1970s, along with detailed SST datasets at several sites along Kochi's >700 km coastline. In order to provide a clear picture of distributional shifts of coastal marine organisms in response to warming SST, we observed the present distribution of seaweeds and analyzed the SST datasets to estimate spatiotemporal SST trends in this coastal region. We present a large increase of 0.3°C/decade in the annual mean SST of this area over the past 40 years. Furthermore, a comparison of the previous and present distributions clearly showed the contraction of temperate species' distributional ranges and expansion of tropical species' distributional ranges in the seaweeds. Although the main temperate kelp Ecklonia (Laminariales) had expanded their distribution during periods of cooler SST, they subsequently declined as the SST warmed. Notably, the warmest SST of the 1997–98 El Nino Southern Oscillation event was the most likely cause of a widespread destruction of the kelp populations; no recovery was found even in the present survey at the formerly habitable sites where warm SSTs have been maintained. Temperate Sargassum spp. (Fucales) that dominated widely in the 1970s also declined in accordance with recent warming SSTs. In contrast, the tropical species, S. ilicifolium, has gradually expanded its distribution to become the most conspicuously dominant among the present observations. Thermal gradients, mainly driven by the warming Kuroshio Current, are presented as an explanation for the successive changes in both temperate and tropical species' distributions.

Sargassum muticum (Yendo) Fensholt is one of the most well-known invasive species in the world. There have, however, been few genetic investigations on both its introduced and native populations. There are also some questions about the taxonomic status of this species. This study is the first to assess the genetic diversity of S. muticum on a global scale, by utilizing one marker each from the extranuclear genomes, namely, plastidial RUBISCO and mitochondrial TrnW_I spacers, as well as the nuclear internal transcribed spacer 2 (ITS2). Based on the markers investigated, both the invasive as well as the native populations of this species appeared very homogenous, when compared with other invasive and brown macroalgae. No variation in ITS2 and RUBISCO spacer was revealed in S. muticum populations, including those from its native ranges in Asia and the introduced ranges in Europe and North America. Two TrnW_I spacer haplotypes with a fixed two-nucleotide difference were found between the populations of eastern Japan and the other 15 populations examined. This study confirms that there is no cryptic diversity in the introduced range of this species. All the materials collected globally are indeed S. muticum. Results depicting the distribution range of the two TrnW_I spacer haplotypes also support the earlier suggestion that the source of the introduced S. muticum populations is most likely western and central Japan (Seto Inland Sea), where the germlings of S. muticum were likely to have been transported with the Pacific oysters previously introduced for farming in Canada, UK, and France in earlier years.

The green macroalga Ulva L. is well known as having an alternation of isomorphic biphases: gametophyte and sporophyte. However, an examination of the temporal alternation in phase dominance has not been carried out. By inducing reproduction of thallus samples in the laboratory, this study reports the temporal changes in the two phases and sex ratios in a natural population of Ulva pertusa Kjellm. in the Seto Inland Sea, Japan, over a period of >3 years. The results showed that a temporal alternation in phase dominance occurred after 11–20 months; seasonal changes in phase dominance were not observed in the Ulva population. The sex ratio of male and female gametophytes remained ∼1:1 throughout the investigated period, although skewed sex ratios were observed in several collections.

Monostroma latissimum (Kuetzing) Wittrock is a monostromatic green alga of commercial importance in Japan. Here we report the serendipitous discovery of asexually reproducing specimens collected from Usa, on the Pacific coast of Kochi Prefecture, south-western Japan. Zoids were found to be biflagellate and negatively phototactic. Germination of settled zoids was observed to follow erect-filamentous ontogeny similar to that of the previously reported sexual strain. Moreover, the newly discovered asexual strain had identical sequences of nuclear encoded ITS (Internal Transcribed Spacer) region to that of the sexual strain. On the basis of this finding, we postulate that the ITS sequences may have been maintained in these conspecific strains despite the evolution in sexuality. Relationships were investigated among M. latissimum and other monostromatic taxa within the class Ulvophyceae using ITS sequences in order to understand relative phylogenetic position of this species.

SUMMARY Ulva limnetica Ichihara et Shimada, sp. nov. (Ulvales,Ulvophyceae) is described from the Ryukyu Islands,Japan, and is characterized by thalli that are: (i)branched, tubular, fragile and wrinkled; (ii) up to 80 cmin height and up to 2 cm in diameter; (iii) light toyellowish green in color; and (iv) having an asexualreproduction by means of quadriflagellate swarmers.Rhizoidal cells bear tubular extensions on the outsideof the cell layer in the stipe. Ulva limnetica is distin-guished from species with similar thalli by chloroplastdisposition, branching pattern, number of pyrenoidsper cell and gross morphology. It is also distinguishedby sequences of the nuclear-encoded 18S ribosomalRNA gene, internal transcribed spacer 2 region andthe plastid-encoded large subunit of ribulose-1,5-bisphosphate carboxylase/oxgenase gene ( rbc L). Ulvalimnetica was clustered with other Ulva species in anearly diverging lineage within the genus.Key words: molecular phylogeny, morphology, rbc L,taxonomy

Monostroma latissimum (Kutzing) Wittrock is an intertidal rock-dwelling green algal species of commercial importance in Japan. This article reports on the seasonality of its growth and occurrence from three distinct habitats of marine and estuarine regions in Tosa Bay, Japan, for two consecutive growth seasons. Thallus lengths of individuals and environmental parameters were monitored monthly between November 2005 and July 2007. Culture studies were carried out to establish the species-level identity of the specimens. Nuclear encoded ITS 1 (Internal Transcribed Spacer 1) sequences reveal that the naturally occurring strain of M. latissimum has identical nucleotide sequences to those of the commercially cultivated strain from the Shimanto river estuary. We have also found that the two strains are cross-fertilizing. Seasonal fluctuations in thallus length were found to be distinctive to the habitat where the strain grows and re-occur annually. Algal cover was highest during winter months and lowest during the summer. However, we found only a very weak positive correlation between chosen environmental parameters and thallus length. Appearance and decay of thalli occurred earlier in high saline habitats. Therefore, it is likely that salinity influences the maturation of microscopic sporophytes or the growth and survival of germlings in M. latissimum.

Sex ratios mediated by environmental conditions are a commonly perceived mechanism through which offspring quality is influenced in many biological systems, but little empirical evidence exists for this complementarity among algal species. This study tries to relate fluctuations in the secondary sex ratio (in nature) of rocky intertidal seaweed Monostroma latissimum (Kutz.) Wittr. to habitat and seasonality. The sex ratio was estimated as roughly 1:1 at all the habitats. Given an approximately even sex ratio at maturity, there seems to be no environmental factor that differentially influences the in-situ survival of male or female gametophytes.

The nuclear-encoded ITS and associated 5.8S rDNA regions were sequenced for 72 specimens of Ulva collected from 44 rivers across Japan, including U. prolifera Muller from the Shimanto River, Kochi Prefecture, as well as 26 samples originally identified as U. linza L. from 20 coastal marine areas. Sequence data revealed that the samples fall into six distinct clades: the U. flexuosa Wulfen clade (2 samples), the Ulva linza-procera-prolifera (LPP) complex clade (75 samples), Ulva sp. 1 clade (3 samples), Ulva sp. 2 clade (7 samples), Ulva sp. 3 clade (4 samples) and Ulva sp. 4 clade (7 samples). The LPP complex contained a mixture of 26 samples collected from seashores and 49 samples obtained from rivers, including U. prolifera from the Shimanto River, and GenBank data for U. linza and U. procera Ahlner. The samples of the LPP complex differed by only 0–7 substitutions (0–1.149%). Subsequent phylogeographic analyses of the LPP complex based on the 5S rDNA spacer region revealed the presence of two further groupings: a group including 22 strictly marine littoral U. linza samples and a U. prolifera group composed of a mixture of 4 marine samples and all 49 river samples. The monophyly of all river samples indicates that adaptation to low salinity might have occurred only once in the evolutionary history of the LPP complex.

BACKGROUND: Sea algae cellulose has been little utilized because the cellulose content in sea algae is low. For the effective utilization of sea algae cellulose, cellulose must be converted without drying into valuable material with a high rate and yield. From this viewpoint, effects of hydrothermal pretreatments of sea algae to enhance the glucose production by enzymatic hydrolysis of sea algae cellulose were investigated. RESULTS: Using hydrothermal pretreatment performed at 423 K for Monostroma nitidum Wittrock (green alga) and at 473 K for Solieria pacifica (red alga) for 30 min, yields of extracted water-soluble components containing monosaccharides were 0.51 g g−1 for the green alga and 0.62 g g−1 for the red alga. The apparent rate of glucose production from hydrothermally pretreated green alga by enzymatic hydrolysis was > 10 times faster than that of the non-pretreated sample. Yields of glucose from cellulose by enzymatic hydrolysis were 79.9% for the green alga and 87.8% for the red alga. CONCLUSION: Cellulose of sea algae was successfully fractionated by hydrothermal pretreatments, which resulted in high susceptibility of sea algae cellulose to enzyme attack. This process leads to the effective utilization of sea algae cellulose. Copyright © 2008 Society of Chemical Industry

The intraspecific genetic diversity of the kelp Undaria pinnatifida (Harvey) Suringar (Laminariales, Phaeophyceae) was investigated using DNA sequences of the mitochondrial cytochrome oxidase subunit 3 (cox3) gene and internal transcribed spacer 1 (ITS1) of nuclear ribosomal DNA in plants collected from 21 localities along the Japanese coast between 2001 and 2003. Morphological variation was also examined and compared with the genetic diversity. Cox3 analyses of 106 plants revealed 9 haplotypes (I–IX) that differed from each other by 1–7 bp (all synonymous substitutions). Haplotype I was distributed in Hokkaido and the northern Pacific coast of Honshu, while haplotype III was found along the Sea of Japan coast of Honshu. Other types were found along the central and southern coast of Honshu. ITS1 analyses of 42 plants revealed 0–1.7% nucleotide differences, but plants from the Sea of Japan coast and northern Japan had similar sequences. The lower genetic differentiation along the Sea of Japan and northern coasts might be due to the recent establishment (after the middle of the last glacial period) of the Sea of Japan flora. The cox3 haplotype of cultivated plants was found in natural populations occurring close to cultivation sites (Naruto, Tokushima Pref., and Hokutan, Hyogo Pref.). This suggests that cultivated plants possibly escaped and spread or crossed with plants of natural populations. Morphological analyses of variation in 10 characters were conducted using 66 plants. The results showed no significant local variation owing to the wide variation in each population and did not support any forma previously described. No correlations between the morphological characters and cox3 haplotypes were detected.

SUMMARY Ulva ohnoi Hiraoka et Shimada sp. nov. (Ulvales, Ulvophyceae) is described from southern and western Japan and is characterized by the following combination of features: (i) the large, fragile, easily torn thalli, which are 30–55 μm thick in the upper and middle regions and often have microscopic marginal teeth; (ii) the production of zoids in the upper marginal region; (iii) a regular alternation of dioecious gametophytes and a sporophyte; (iv) the production of free-floating thalli from torn-off attached thalli, which reproduce vegetatively by fragmentation and form green tides in summer to autumn; (v) disorderly arranged cells that are polygonal or quadrangular in the upper and middle regions; and (vi) the chloroplast covering the outer face of cell, with 1–3 pyrenoids. Ulva ohnoi differs from U. armohcana Dion et al., U. fasciata Delile, U. reticulata Forsskal, U. scandinavica Eliding and U. spiulosaOkamura et Segawa, which all possess microscopic marginal serrations, in thallus shape, cell shape or life history pattern. It is also distinguished from morphologically similar species by sequences of the nuclear encoded internal transcribed spacers and the 5.8S ribosomal RNA gene and the plastid encoded large subunit of ribulose-l,5-bisphosphate carboxylase/oxgenase gene. Furthermore, crossing tests demonstrate that there is a reproductive boundary between U. ohnoi and the most closely related species, U. fasciata and U. reticulata.

Ulva spp. are common in the intertidal zones of the Philippines, but, at certain times, could over-proliferate producing blooms or `green tide' in some protected bays. In Mactan Island (Cebu), central Philippines, at least two species constitute the Ulva population, either as free-living or attached form. The one referred to in the literature as `Ulva lactuca' mainly consists of free-living population while the species referred to as Ulva reticulata consists mainly of attached population. Based on morphological and physiological characteristics, `U. lactuca' differs much from the descriptions of the species from its type locality in Europe in having a crumpled texture of blade, presence of tooth-like protuberances at the margins, thinner thallus (40–50 μm) and more pyrenoids per cell (two to four). The species referred to as `U. lactuca' in the Philippines therefore is a different species. Two morphotypes consisted the `U. lactuca' population from Mactan – a thick thallus and a thin thallus type. However, both morphotypes cultured under the same condition in the laboratory could transform into the same thin-thallus type observed in the field. `Green tide' caused by `U. lactuca' occur almost regularly in Station 1 of Mactan Island, reaching an average biomass of up to 2.6 kg wet wt m−2 (or 0.5 kg dry wt m−2). Ulva reticulata, although was less abundant in the rocky tidal zone at most times, reaching an average biomass of only up to 0.15 kg wet wt m−2 (or 0.03 kg dry wt m−2) had caused green tide in Station 2 around February–March. Reproductive structures were not observed in both Ulva species during the survey period suggesting that vegetative fragmentation is the main mode of propagation. Vegetative tissues excised from the thallus can be induced to release biflagellated large and small zooids.