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Three benthic Gyrosigma species isolated from sediments of a tropical mangrove in Hainan Island, China, are described using light, scanning and transmission electron microscopy: G. centropunctatum ...

In the current study, 334 specimens of Pterocladiella from China representing historical herbarium specimens and recent field collections were re-examined based upon morphological and molec...

An edible green algal species Caulerpa lentillifera J. Agardh is reported from China for the first time. The species was collected from the southwest of Hainan Island and morphologically identified...

© 2019 Japanese Society of Phycology Flattened Gracilaria species are widely distributed along the coasts of the South China Sea with more than 20 species recorded. Within the South China Sea, Gracilaria mammillaris has only been reported from Vietnam, but this species is likely restricted to the western Atlantic. This study aimed to reevaluate the taxonomic status of Vietnamese specimens of ‘G. mammillaris’ using combined morphological and molecular data. Our data clearly indicated that Vietnamese specimens were morphologically and genetically distinct from authentic G. mammillaris from the western Atlantic, and also other described flat Gracilaria species. We, therefore, propose that specimens from Vietnam originally identified as G. mammillaris be designated as a new species, Gracilaria phuquocensis sp. nov. Morphologically, G. phuquocensis can be distinguished from other flat Gracilaria species by its small thallus size, narrower blades, many medullary layers, abundant basal nutritive filaments within mature cystocarps, and tetrasporangial nemathecium. Our rbcL sequence analyses showed that the new species was sister to Gracilaria rhodymenioides from Thailand, and these two species formed a clade with cylindrical Gracilaria species. Our study contributes to clarification of the taxonomic status of misidentified specimens attributed to the flattened Gracilaria species in the South China Sea.

Molecular phylogeny of Eudesme specimens collected from various localities in the Northern Hemisphere using mitochondrial cox1 and cox3 and chloroplast atpB, psaA, psbA and rbcL gene sequen...

To examine optimal growth conditions of the edible green alga Caulerpa okamurae, thalli of this species were cut into erect frond (3 cm long) and stolon (5 cm long) fragments. They were cultured in combinations of four temperatures (15, 20, 25, and 30 °C), three irradiances (20, 40, and 80 μmol photons m−2 s−1), four daylengths (8, 12, 16, and 24 h), and seven salinities (15, 20, 25, 30, 35, 40, and 45 psu). After 12 days, maximal relative growth rates (RGRs) for erect fronds (6.78% day−1) and stolons (7.02% day−1) occurred at 25 °C and 40 μmol photons m−2 s−1. At 30 °C, growth differences were found; negative growth for erect fronds and positive growth for stolons, with an average RGR of 1.96% day−1. A daylength of 16 h and salinity of 30 psu were needed for maximal growth of erect fronds and stolons. Stolon exhibited a greater tolerance to high and low temperatures and low salinity than erect fronds. Thalli weight of C. okamurae was increased by increments of stolon length, new erect fronds, and new ramuli. In conclusion, C. okamurae should be cultivated in summer with high seawater temperature (25 °C) and long daylength, in waters of 30 psu, and at a water depth providing 40 μmol photons m−2 s−1. These physiological and growth pattern data are informative for the successful development of commercial cultivation of C. okamurae.

International audience; The tropical to warm-temperate marine brown macroalgal genus Lobophora (Dictyotales, Phaeophyceae) recently drew attention because of its striking regional diversity. In this study we reassess Lobophora global species diversity, and species distributions, and explore how historical factors have shaped current diversity patterns. We applied a series of algorithmic species delineation techniques on a global mitochondrial cox3 dataset of 598 specimens, resulting in an estimation of 98–121 species. This diversity by far exceeds traditional diversity estimates based on morphological data. A multi-locus time-calibrated species phylogeny using a relaxed molecular clock, along with DNA-confirmed species distribution data was used to analyse ancestral area distributions, dispersal-vicariance-founder events, and temporal patterns of diversification under different biogeographical models. The origin of Lobophora was estimated in the Upper Cretaceous (−75 to −60 MY), followed by gradual diversification until present. While most speciation events were inferred within marine realms, founder events also played a non-negligible role in Lobophora diversification. The Central Indo-Pacific showed the highest species diversity as a result of higher speciation events in this region. Most Lobophora species have small ranges limited to marine realms. Lobophora probably originated in the Tethys Sea and dispersed repeatedly in the Atlantic (including the Gulf of Mexico) and Pacific Oceans. The formation of the major historical marine barriers (Terminal Tethyan event, Isthmus of Panama, Benguela upwelling) did not act as important vicariance events. Long-distance dispersal presumably represented an important mode of speciation over evolutionary time-scales. The limited geographical ranges of most Lobophora species, however, vouch for the rarity of such events.

Lobophora rosacea C.W. Vieira, Payri et De Clerck is reported from the South China Sea for the first time. Our specimens are very similar to L. rosacea recently described from New Caledonia, not only in morphology but also in rbcL and cox3 gene sequences. The fan-shaped thallus grows erectly, attaching to the substrate by a basal holdfast. The thallus is composed of a single layer of large medullary cells and three to four layers of cortical cells on both sides of the medulla. Mature sporophytes are detected, with sporangium sori scattered on both surfaces of the thallus.

A major goal of phylogeographic analysis using molecular markers is to understand the ecological and historical variables that influence genetic diversity within a species. Here, we used sequences of the mitochondrial Cox1 gene and nuclear internal transcribed spacer to reconstruct its phylogeography and demographic history of the intertidal red seaweed Chondrus ocellatus over most of its geographical range in the Northwest Pacific. We found three deeply separated lineages A, B and C, which diverged from one another in the early Pliocene-late Miocene (c. 4.5-7.7 Ma). The remarkably deep divergences, both within and between lineages, appear to have resulted from ancient isolations, accelerated by random drift and limited genetic exchange between regions. The disjunct distributions of lineages A and C along the coasts of Japan may reflect divergence during isolation in scattered refugia. The distribution of lineage B, from the South China Sea to the Korean Peninsula, appears to reflect postglacial recolonizations of coastal habitats. These three lineages do not coincide with the three documented morphological formae in C. ocellatus, suggesting that additional cryptic species may exist in this taxon. Our study illustrates the interaction of environmental variability and demographic processes in producing lineage diversification in an intertidal seaweed and highlights the importance of phylogeographic approaches for discovering cryptic marine biodiversity.

Many studies classifying Gracilaria species for the exploitation of agarophytes and the development of the agar industry were conducted before the prevalence of molecular tools, resulting in the description of many species based solely on their morphology. Gracilaria firma and G. changii are among the commercially important agarophytes from the western Pacific; both feature branches with basal constrictions that taper toward acute apices. In this study, we contrasted the morpho-anatomical circumscriptions of the two traditionally described species with molecular data from samples that included representatives of G. changii collected from its type locality. Concerted molecular analyses using the rbcL and cox1 gene sequences, coupled with morphological observations of the collections from the western Pacific, revealed no inherent differences to support the treatment of the two entities as distinct taxa. We propose merging G. changii (a later synonym) into G. firma and recognize G. firma based on thallus branches with abrupt basal constrictions that gradually taper toward acute (or sometimes broken) apices, cystocarps consisting of small gonimoblast cells and inconspicuous multinucleate tubular nutritive cells issuing from gonimoblasts extending into the inner pericarp at the cystocarp floor, as well as deep spermatangial conceptacles of the verrucosa-type. The validation of specimens under different names as a single genetic species is useful to allow communication and knowledge transfer among groups from different fields. This study also revealed considerably low number of haplotypes and nucleotide diversity with apparent phylogeographic patterns for G. firma in the region. Populations from the Philippines and Taiwan were divergent from each other as well as from the populations from Malaysia, Thailand, Singapore and Vietnam. Establishment of baseline data on the genetic diversity of this commercially important agarophyte is relevant in the context of cultivation, as limited genetic diversity may jeopardize the potential for its genetic improvement over time.

Using light, scanning and transmission electron microscopy, and SSU rDNA and rbcL gene sequencing, we investigated three marine benthic diatoms: Haslea avium Tiffany, Herwig et Sterrenburg; H. feriarum Tiffany et Sterrenburg and H. tsukamotoi Sterrenburg et Hinz collected from intertidal sediments in China. These are the first records of these three species from China. Our observations showed that the typical valve structure of Haslea, with an inner basal layer and an outer tegumental layer, and walls (saepes sensu Sterrenburg et al.) between them is not present in either H. tsukamotoi or H. avium. Moreover, the two species possess small helictoglossae, an internal apical thickened area and hooked terminal fissures reaching to the valve mantle, suggesting a close relationship with Navicula tripunctata, the type species of Navicula s.s. In molecular phylogenetic analyses, Haslea was polyphyletic, being divided into two separate clades: H. feriarum belonged to a clade that comprised only Haslea species, including the type H. ostrearia, while H. tsukamotoi and H. avium were within the Navicula clade. Therefore, we propose transferring H. tsukamotoi and H. avium to Navicula and suggest that the presence of continuous longitudinal strips on the external valve surface is not a synapomorphy, but rather a homoplastic character for Haslea.

Caulerpa lentillifera is a green algae that distributes worldwide and is cultivated for food. We assessed vegetative propagation of C. lentillifera by measuring the specific growth rate (SGR) and chlorophyll fluorescence of the green algae cultured at different salinities and nutrient levels. The results indicated that C. lentillifera can survive in salinities ranging from 20 to 50, and can develop at salinities of 30 to 40. The maximum SGR for C. lentillifera occurred at a salinity of 35. Both chlorophyll content and the ratio of variable to maximum fluorescence (Fv/Fm) were also at a maximum at a salinity of 35. Photosynthesis was inhibited in salinities greater than 45 and less than 25. Both the maximum SGR and maximum chlorophyll content were found in algae treated with a concentration of 0.5 mmol/L of NO3-N and 0.1 mmol/L of PO4-P. The photosynthetic capacity of photosystem II (PSII) was inhibited in cultures of C. lentillifera at high nutrient levels. This occurred when NO3-N concentrations were greater than 1.0 mmol/L and when PO4-P concentrations were at 0.4 mmol/L. As there is strong need for large-scale cultivation of C. lentillifera, these data contribute important information to ensure optimal results.

In order to study the effect of temperature, irradiance, and salinity on the asexual reproduction of Caulerpa lentillifera, we conducted the indoor culture to study these factor effects on the regeneration of C. lentillifera, together with the measurement of photosynthetic parameters such as chlorophyll content, fluorescence characteristics, and rbcL behavior. It was shown that the maximum specific growth rate (SGR) of the alga was at 27.5 A degrees C and 40 mu mol photons m(-2) s(-1), and warm temperature (25.0-30.0 A degrees C) induced the formation of branches. Both lower and higher temperature reduced chlorophyll content and decreased F (v)/F (m) value, while high rbcL expressions occurred at 27.5 A degrees C. With the irradiance rise, the chlorophyll content decreased and the higher irradiance (100 mu mol photons m(-2) s(-1)) decreases F (v)/F (m) and increases of NPQ. The higher irradiances (40 and 100 mu mol photons m(-2) s(-1)) also reduced rbcL expression. This physio-ecological data will be valuable to explore the possible asexual propagation of this green alga and eventually for future large-scale vegetative reproduction.

The whole chloroplast genome (cp DNA) sequence of Caulerpa lentillifera J. Agardh has been characterized from Illumina pair-end sequencing. The circular cpDNA was 119,402 bp in length, containing 122 genes, which included 91 protein-coding genes, 28 tRNA genes, and 3 ribosomal RNA genes (four rRNA species). The overall AT content of C. lentillifera cpDNA is 67.4%. The 48 genes phylogenetic analysis suggested that C. lentillifera formed a monophyletic clade with congeneric C. racemosa.

Sun Z., Hanyuda T., Lim P.E., Tanaka J., Gurgel C.F.D. and Kawai H. 2012. Taxonomic revision of the genus Lobophora (Dictyotales, Phaeophyceae) based on morphological evidence and analyses rbcL and cox3 gene sequences. Phycologia 51: 500–512. DOI: 10.2216/11-85.1 A taxonomic revision of Lobophora based on molecular phylogenetic analyses of rbcL and cox3 gene sequences as well as anatomical observations was carried out, mostly based on specimens collected from eastern Asia and southeastern Australia. In the molecular phylogenetic analyses, nine major clades supported by high bootstrap values were recognized. In combination with evaluation of morphological characters, four clades were concluded to be new species. The Australian species L. australis sp. nov. possessed erect thalli with sporangial sori scattered on the ventral surface and had a closer phylogenetic relationship with another Australian species, L. nigrescens, but it was distinguished from the latter in having fewer layers of cortical cells and ...

BackgroundPopulation structure and genetic diversity of marine organisms in the Northwestern Pacific Ocean exhibited complex patterns.Saccharina japonicais a commercially and ecologically important kelp species widely distributed along the coast of Japan Sea. However, it is still poorly known about population genetics and phylogeographic patterns of wildS. japonicapopulations on a large geographic scale, which is an important contribution to breeding and conservation of this marine crop.ResultsWe collected 612 mitochondrialCOIandtrnW-trnL sequences. Diversity indices suggested thatS. japonicapopulations along the coast of Hokkaido exhibited the highest genetic diversity. Bayesian Analysis of Population Structure (BAPS) revealed four clusters in the kelp species (cluster 1: Hokkaido and South Korea; cluster 2: northwestern Hokkaido; cluster 3: Far Eastern Russia; cluster 4: China). The network inferred from concatenated data exhibited two shallow genealogies corresponding to two BAPS groups (cluster 2 and cluster 3). We did not detect gene flow between the two shallow genealogies, but populations within genealogy have asymmetric gene exchange. Bayesian skyline plots and neutrality tests suggested thatS. japonicaexperienced postglacial expansion around 10.45 ka.ConclusionsThe coast of Hokkaido might be the origin and diversification center ofS. japonica. Gene exchange amongS. japonicapopulations could be caused by anthropogenic interference and oceanographic regimes. Postglacial expansions and gene exchange apparently led to more shared haplotypes and less differentiation that in turn led to the present shallow phylogeographical patterns inS. japonica.

The species-level taxonomy of the marine brown algal genus Sargassum is problematic. To resolve some of these systematic issues in the northern China seas, a molecular analysis of Sargassum species was carried out using ITS-2, cox3, and rbcL DNA sequences. Phylogenetic analyses confirmed eight species, including: S. confusum, S. fusiforme, S. hemiphyllum var. chinense, S. horneri, S. muticum, S. siliquastrum, S. thunbergii, and S. vachellianum. The previously described S. shandongense and S. qingdaoense, endemic to the Shandong Peninsula, are shown to be synonymous with S. vachellianum. Seven species previously described from the East China Sea were not observed, and require further investigation.

Microcostatus salinus, an epipsammic species, is described from estuarine intertidal sediments in Japan. Its morphology was examined with light, scanning and transmission electron microscopy. Microcostatus salinus possesses two unique morphological features differing from all other species in this genus, viz., i) the striae are composed of two elongate areolae and restricted to the area near valve apexes, and ii) the distance between the two central raphe endings on the external valve surface is about two times longer than that on the internal one. In addition, M. salinus is the only species of the genus Microcostatus found from brackish to saline environments.

Fallacia decussata is described as a new marine littoral diatom from Northeast Asia. Its morphology was examined with light, scanning and transmission electron microscopy. Fallacia decussata has a unique feature, viz., possessing 2–4 pores on each side of raphe terminal fissures, while all congeners have either invariably a single pore or only a slit. This species differs from congeners also by a combination of morphological features including: i) elliptical valves with broadly round poles; and ii) convex and centrally strongly constricted lateral sterna, forming a more or less X-shaped central area; iii) striation density of 25–28 in 10 μm. This species is an epipsammic diatom currently known from intertidal zone in the northwest Pacific Ocean.

Molecular phylogenetic analyses based on plastid-encoded rbcL and mitochondrial cox3 gene sequences, in combination with morphological observations, revealed the existence of the following four bistratose Padina species previously unreported from Australian coasts: Padina calcarea Ni-Ni-Win, S.G.A.Draisma, W.F.Prud'homme van Reine & H.Kawai, characterised by its bright yellow–orange inferior thallus surface and chalky white, heavily calcified superior surface, and the presence of hairlines only on the inferior surface; P. macrophylla Ni-Ni-Win, M.Uchimura & H.Kawai, characterised by a moderately calcified thallus with broad, depressed hairlines on the inferior surface and narrow, not depressed hairlines on the superior surface, those hairlines that are largely spaced on each surface; P. moffittiana I.A.Abbott & Huisman, characterised by lightly calcified thalli with narrow, slightly depressed hairlines that are distributed in alternate sequence between the two surfaces at unequal distances, and broad reproductive sori in one or two rows in the fertile zone; and P. okinawaensis Ni-Ni-Win, S.Arai, M.Uchimura & H.Kawai, characterised by heavily calcified thalli, except at the hairlines, which form an alternation of uncalcified furrows and calcified glabrous zones on the inferior surface. With the addition of these four species, 13 Padina species are known from Australia.