Chemical races in the red alga Laurencia nipponica (Rhodomelaceae, Ceramiales)

Genetic variation in the synthesis of halogenated secondary metabolites in the Japanese marine red alga Laurencia nipponica Yamada (Rhodomelaceae, Ceramiales) has been investigated in laboratory crossing experiments and chemical analyses, F₁ tetrasporophytes and F₁ gametophytes resulting from crosses within chemical races produced major metabolites characteristic of these races. F₁ tetrasporophytes derived from reciprocal interracial crosses produced: (i) both parental types of secondary metabolites; (ii) either of the parental types; or (iii) a further major compound in addition to both parental types or in addition to either of the parental types. The latter cases suggest that hybrid-specific products were formed by the combined enzymatic complements of the parents, as F₁ gametophytes derived from these interracial F₁ tetrasporophytes yielded one or other of their parental products in an approximate 1:1 ratio. The population structure was analyzed at localities in Hokkaido, where two of the chemical races occur sympatrically. At Usujiri (Minami-kayabe), where the prepacifenol race and the laureatin race were sym-patric, hybrid gametophytes (recombination type) were found in high frequency in addition to hybrid tetra sporophytes, which strongly suggests that a new, pre-pacifenol/laureatm race is beginning to be produced by natural hybridization and recombination. By contrast, at Oshoro Bay, where the laurencin race and the epi-lauraliene race grew together, the interracial hybrids were rare: only a few tetrasporophytes (probably F₁ generation) were found, suggesting that racial integrity may be retained by habitat segregation and/or the absence of recombination-type gametophytes.     

Ultrastructure of post-fertilization development in the red alga Nienburgia andersoniana (Delesseriaceae, Ceramiales, Rhodophyta)

The ultrastructure of post-fertilization development in Nienburgia andersoniana (J. Ag.) Kyl. is described. Above the auxiliary cell there is a group of four sterile cells. The presence of abundant storage products (starch granules, lipid bodies and protein crystals) in these cells indicates that the sterile cells function as nutrient suppliers to the young auxiliary and gonimoblast cells of the carposporophyte during its early steps of development. Following fertilization and transfer of the diploid nucleus to the auxiliary cell, the trichogyne disappears and large multinucleate gonimoblast initials are produced. These subsequently produce generative gonimoblast cells which cleave successively to form young carpospores. Those of the gonimoblast cells which will not differentiate into carpospores are transformed into cells producing mucilage. Both kinds of gonimoblast cells contain plastids, starch granules, cytoplasmic concentric membrane bodies and small vesicles. Dark-staining spherical masses occurring in the cytoplasm of the auxiliary and gonimoblast cells may represent degenerating haploid nuclei. Septal plugs interconnecting the auxiliary cell and gonimoblast cells increase considerably in size during carposporophyte development. The fusion cell at the late stage of carposporophyte development appears degenerative. Young carpospores have plastids and mitochondria, and concentric membrane bodies that will form mucilage sacs. Medium-aged carpospores have fully developed plastids, starch granules and fibrous vacuoles. Mature carpospores possess, in addition, cored vesicles. The inner pericarp cells contribute large amounts of mucilage to the cytostocarpic cavity and eventually are consumed. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 289–299.     

Ultrastructure of post-fertilization development in the red alga Scinaia articulata (Galaxauraceae,Nemaliales, Rhodophyta)

The ultrastructure of the carposporophyte and carposporogenesis is described for the red alga Scinaia articulata Setch. After fertilization, the trichogyne disappears, and the pericarp develops to form a thick protective tissue that surrounds the carposporophyte. The hypogynous cell cuts off both one-celled and two-celled sterile branches. Patches of chromatin are frequently observed in evaginations of the nuclear envelope, which appear to produce vesicles in the cytoplasm of the cell of the sterile branch. Large gonimoblast lobes extend from the carpogonium and cleave to form gonimoblast initials. Subsequently, a fusion cell is formed from fusions of the carpogonium, the hypogynous cell and the basal cell of the carpogonial branch. The mature carposporophyte comprises the fusion cell that is connected to the sterile branch cells, gonimoblast cells and carpospores and is surrounded by extensive mucilage. Young carpospores possess a large nucleus and proplastids with a peripheral thylakoid, but they have few dictyosomes and starch granules and are indistinguishable from gonimoblast cells. Subsequently, dictyosomes are formed, which produce vesicles with an electron-dense granule, which indicates an initiation of wall deposition. Thylakoid formation coincides with incipient starch granule deposition. The nuclear envelope produces fibrous vacuoles and concentric membrane bodies. Carpospores are interconnected by pit connections with two cap layers. Dictyosome activity increases, resulting in the production of vesicles, which either continue to deposit wall material or coalesce to form fibrous vacuoles. The final stage of carposporogenesis is characterized by the massive production of cored vesicles from curved dictyosomes. Mature carpospores are uninucleate and contain fully developed chloroplasts, numerous cored vesicles, numerous starch granules and fibrous vacuoles. The mature carpospore is surrounded by a wall layer and a separating layer, but a carposporangial wall is lacking.     

Ultrastructure of the early stages of carposporophyte development in the red algaChondria tenuissima (Rhodomelaceae,Ceramiales)

The ultrastructure of the early stages of carposporophyte development in the marine red algaChondria tenuissima has been studied. The diploid carposporophyte grows on the gametophyte. Apical gonimoblast cells develop into diploid carpospores. The basal gonimoblast cells cease to divide and undergo considerable cytoplasmic changes before they become incorporated into the expanding fusion cell. Nucleus and plastids degenerate gradually, while mitochondria remain intact. The smooth endoplasmic reticulum becomes prominent, it seems to produce small vesicles with electron dense contents. Simultaneously, numerous mucilage sacs are formed, presumably from dilating ER cisternae. The contents of the mucilage sacs are secreted by exocytosis. The pit connections between gonimoblast cells flare out. They remain as isolated bodies without connection to a wall after fusion. Secondary pit connections occur between vegetative gametophyte cells and sterile carposporophyte cells. There are three different morphological types of pit connections.     

Pterosiphonia tanakae (Rhodomelaceae, Ceramiales), a new red algal species from Japan

The red alga Pterosiphonia tanakae Uwai et Masuda (Rhodomelaceae, Ceramiales) is established as a new species on the basis of material collected in Hiroshima Bay, the Inland Sea, Japan. It can be distinguished from the majority of previously described species of the genus by two key features, seven to 10 periaxial cells and the presence of weakly developed cortical cells. This species is further distinguished from P. pau-cicorticata Dawson by completely alternate-distichously branching and from Pjavanica (Martens) De Toni and P. spinifera (Kützing) Norris et Aken by the production of first-order laterals that bear branches of up to five orders, which results in the thallus having a widely spreading, fan-shaped appearance. The abundant production of vegetative trichoblasts is a further characteristic feature of P. tanakae.     

Development of the red algal parasite Vertebrata aterrimophila sp. nov. (Rhodomelaceae,Ceramiales) from New Zealand

Parasitic red algae grow only on other red algae and have over 120 described species. Developmental studies in red algal parasites are few, although they have shown that secondary pit connections formed between parasite and host and proposed that this was an important process in successful parasitism. Furthermore, it was recorded that the transfer of parasite nuclei by these secondary pit connections led to different host cell effects. We used developmental studies to reconstruct early stages and any host cell effects of a parasite on Vertebrata aterrima. A mitochondrial marker (cox1) and morphological observations (light and fluorescence microscopy) were used to describe this new red algal parasite as Vertebrata aterrimophila sp. nov. Early developmental stages show that a parasite spore connects via secondary pit connections with a pericentral host cell after cuticle penetration. Developmental observations revealed a unique connection cell that grows into a ‘trunk-like’ structure. Host cell transformation after infection by the parasite included apparent increases in both carbohydrate concentrations and nuclear size, as well as structural changes. Analyses of molecular phylogenies and reproductive structures indicated that the closest relative of V. aterrimophila is its host, V. aterrima. Our study shows a novel developmental parasite stage (‘trunk-like’ cell) and highlights the need for further developmental studies to investigate the range of developmental patterns and host effects in parasitic red algae.     

Ultrastructure of Euglena anabaena var. minor (Euglenophyceae)

The freshwater green euglenoid Euglena anabaena var. minor has a pellicle with groove‐ridge articulation, a chloroplast with pyrenoids doubly sheathed by two paramylon caps, and a nucleus with permanently condensed chromosomes and nucleolus. The flagellar apparatus basically resembles that of Euglena. The dorsal root (DR) originates at the dorsal basal body of the emergent flagellum, while both the intermediate root (IR) and ventral root (VR) originate at the ventral basal body of the non‐emergent flagellum. The cytoplasmic pocket is associated with the ventral root/ reinforcing microtubular band. However, ultrastructural characterization of E. anabaena var. minor shows the pocket to consist of five to seven microtubules, and flagellar roots with microtubule configuration of 3–4–6 in the DR‐IR‐VR. The dorsal band microtubules pair at the reservoir‐canal transition level. The doublet microtubules are formed into triplets and doublets at the lower canal level and then make pellicular microtubules at the upper canal level.     

Echinophycus minutus (Rhodomelaceae, Ceramiales), a new red algal genus and species from north-western Australia

Echinophycus minutus gen. et sp. nov. (Ceramiales, Rhodophyta) is described for specimens collected from a deep‐water habitat in the Dampier Archipelago, northwestern Australia. Plants were dredged from a coarse sand/rubble habitat, where they were partially decumbent and attached to the substratum by numerous unicellular rhizoids, Thalli are to 25 mm in height, uniaxial, with four pericentral cells and a persistent pigmented trichoblast arising on each axial cell. Tricho‐blasts are arranged in a spiral pattern, with a 90° divergence between successive segments. Each trichoblast is composed of a basal cell bearing a cluster of unbranched filaments. Tetrasporangia are tetrahedral and formed in series in normal branches. Procarps have two sterile cell groups. Spermatangia are formed In heads that are terminal on trichoblasts. The new genus is placed in the tribe Brongniartelleae of the family Rhodomelaceae, differing from all other included genera in the morphology of the trichoblasts.     

Agarans from the red seaweed Polysiphonia nigrescens (Rhodomelaceae, Ceramiales)

Polysiphonia nigrescens was sequentially extracted with water at room temperature, 70 and 90 degrees C. The extracts were analyzed and the major one, isolated at 70 degrees C, was fractionated by ion-exchange chromatography, eluting with water and solutions of increasing sodium chloride concentration; five main fractions were separated. Structural analysis, carried out by methylation analysis and NMR spectroscopy, showed that four of these were partially cyclized agarans that were highly substituted on C-6 mainly with sulfate, although methyl ether and single stubs of beta-D-xylose were found in minor proportions. A fifth fraction comprising 6-sulfated agarose was also isolated. The use of 2D NMR techniques allowed us to assign the 1H and 13C NMR resonances of the G6S-->L6S diad for the first time.     

分株紫萁卵发生的超微结构

用透射电镜对蕨类植物分枝紫萁(Osmunda cinnamamae L. var. asiatica Fernald)卵发牛进行了超微结构的研究。卵发生过程中,许多泡囊不仅移向细胞周围,而且在细胞质膜内排为一列,并通过胞吐作用聚集在细胞质膜外,它们释放或分泌嗜锇物质。观察到少数泡囊内含片层状结构的嗜饿物质紧贴于细胞质膜,似乎将其冲破。与此同时,在卵细胞和颈卵器壁之问形成分离腔,其宽度大于以往报道的真蕨类,在卵细胞质膜外出现额外的卵膜,其宽度大于蕨属和鳞毛蕨属。造粉体被大型常呈三角状半圆形或近椭圆形的淀粉粒所充满,当卵成熟时逐渐减少。核大型平扁状,核内出现2-3对平行的双层膜,紧贴核膜。未发现核外突。线粒体一度似不发育,最后恢复正常。     

分株紫萁卵发生的超微结构

用透射电镜对蕨类植物分枝紫其(Osmunda cinnamamae L. var.asiatica Fernald)卵发生进行了超微结构的研究.卵发生过程中,许多泡囊不仅移向细胞周围,而且在细胞质膜内排为一列,并通过胞吐作用聚集在细胞质膜外,它们释放或分泌嗜锇物质.观察到少数泡囊内含片层状结构的嗜饿物质紧贴于细胞质膜,似乎将其冲破.与此同时,在卵细胞和颈卵器壁之间形成分离腔,其宽度大于以往报道的真蕨类,在卵细胞质膜外出现额外的卵膜,其宽度大于蕨属和鳞毛蕨属.造粉体被大型常呈三角状半圆形或近椭圆形的淀粉粒所充满,当卵成熟时逐渐减少.核大型平扁状,核内出现2~3对平行的双层膜,紧贴核膜.未发现核外突.线粒体一度似不发育,最后恢复正常.     

Morphology of Chondrophycus undulata and C. parvipapillata and its implications for the taxonomy of the Laurencia (Ceramiales,Rhodophyta) complex

Laurencia Lamouroux subgenus Chondrophycus Tokida et Saito was recently raised to generic status as Chondrophycus (Tokida et Saito) Garbary et Harper (Ceramiales, Rhodophyta). The previously unknown morphology and anatomy of two Chondrophycus species, C. undulata (Yamada) Garbary et Harper and C. parvipapillata (C.K. Tseng) Garbary et Harper, were studied in specimens from Korea, Japan and Hawaii. These species share some features, such as a strongly compressed thallus, vegetative axes with two pericentral cells, tetrasporangial production from pericentral cells and spermatangial development of the trichoblast type. However, they differ from each other in the position of the first pericentral cell relative to the trichoblast in axial segments and in the position of the tetrasporangial pericentral cell. In C. undulata, the first pericentral cell is always produced at one side of the basal cell of a trichoblast, whereas in C. parvipapillata it is formed underneath this cell. While tetrasporangia in C. undulata are produced only from three (occasionally four) additional pericentral cells, in C. parvipapillata they are formed by the existing second pericentral cell and two (occasionally three) additional pericentral cells, so the resulting tetrasporangial axial segment has only one sterile pericentral cell rather than two as in C. undulata. C. undulata produces spermatangial branches from two laterals on the suprabasal cell of trichoblasts but one of the two remains partly sterile, whereas in C. parvipapillata a spermatangial branch develops from only one of the two laterals. These two species also differ distinctly from each other in some vegetative features, such as presence or absence of (1) secondary pit connections between epidermal cells, (2) a palisade structure of epidermal cells with conical projections and (3) corps en cerise. The taxonomic implications of these vegetative and reproductive features of Chondrophycus and those of other genera of the Laurencia complex necessitate changes to the generic delineations of Osmundea Stackhouse, Laurencia and Chondrophycus. The required new combinations in Chondrophycus are made, mainly for species from the western Pacific. An infrageneric classification scheme is also proposed for Chondrophycus including Kangjaewonia subgen. nov., Palisada (Yamada) subgen. stat. nov., Yuzurua subgen. nov. and Parvipapillatae sect. nov.     

The reproductive structures of the Mediterranean alga Laurencia pelagosae (Ceramiales,Rhodophyta)

Reproductive structures of Laurencia pelagosae are described for the first time. Tetrasporangia, in parallel arrangement, are cut off from the mother cells adaxially; antheridial branches, which are unramified, are inserted in depressions lacking a row of axial cells on their bases; cystocarps are sessile and subspherical. The occurrence of secondary pit-connections between epidermal cells and of lenticular thickenings in the walls of medullary cells is documented. The species is included in the new section Pelagosae within the subgenus Laurencia.     

The anatomy of Neotenophycus ichthyosteus gen. et sp. nov. (Rhodomelaceae,Ceramiales), a bizarre red algal parasite from the central Pacific

A minute parasite of Neosiphonia poko (Hollenberg) Abbott from a shallow lagoon on the central-Pacific Johnston Atoll is described as Neotenophycus ichthyosteus Kraft et Abbott, gen. et sp. nov. The infective parasite cell first connects to a central-axial cell of the host, then emerges from between host pericentral cells at a node before dividing into a three- or four-celled primary axis. Epibasal cells of the parasite divide to form three pericentral cells whose derivatives produce a globular head on the basal cell and on which reproductive structures differentiate almost immediately. Trichoblasts on any life-history stage are completely lacking. Spermatangia are borne on mother cells across the whole thallus surface. Procarps consist of four pericentral cells that encircle a subapical fertile-axial cell in an ampullar configuration, one of the pericentral cells serving as the supporting cell and bearing a four-celled carpogonial branch and a single sterile cell. Diploidization results in a longitudinal/concave division of the auxiliary cell and formation of an arching linear series of inner gonimoblast cells, each dividing toward the thallus surface into gonimoblast filaments of very narrow, horizontally aligned cells terminated by initially monopodial, later by sympodial, carposporangia, the whole of the mature female gametophyte consisting of an amalgam of several cystocarps within a lax jacket of sterile gametophytic tissue. Tetrasporophytes are composed of lobes of pericentral-cell-derived filaments, each axial cell of which is ringed by three pericentral cells producing tetrahedral tetrasporangia enclosed by two pre-sporangial cover cells. Affinities of the new genus are discussed and comparison is made particularly to the enigmatic parasite Episporium centroceratis Möbius. It is concluded that relationships with any previously described tribe are so remote or obscure that the new tribe Neotenophyceae should be proposed for it.     

蕨类植物分株紫萁精子发生过程中生毛体和多层结构的超微结构

应用电镜技术对蕨类植物分株紫萁(Osmunda cinnamomea L. var．asiatica Fernald)精子发育过程中的生毛体和多层结构的超微结构进行了研究。牛毛体在幼精了细胞中出现,正在分化的生毛体略呈球状,球状体的中央由一团染色深的颗粒状物质构成,外围分化出若干柱状体。已分化的生毛体由柱状体分散或辐射状排列构成,呈球状,球体中心不含染色深的物质。多层结构位于精子细胞内的基体和巨大线粒体之间,刚形成时仅由片层构成,片层相互平行排列形成片层带。多层结构在分化中期由微管带、片层带和蚀斑三层构成。多层结构在分化末期又形成附属微管带、嗜锇冠和嗜锇层。微管带从多层结构长出,沿细胞核的表面伸展,并与核膜之间形成复合结构。基体由柱状体转变而成,它向两端生长,在远端产生鞭毛的轴丝,在近轴端形成楔状结构。本文首次详细阐明了原始薄囊蕨分株紫其生毛体和多层结构发育的超微结构特点,并与其他蕨类进行了比较,发现其片层带出现在微管带形成之前。     

蕨类植物分株紫萁精子发生过程中生毛体和多层结构的超微结构

应用电镜技术对蕨类植物分株紫萁(Osmunda cinnamomea L. var.asiatica Fernald)精子发育过程中的生毛体和多层结构的超微结构进行了研究.生毛体在幼精子细胞中出现,正在分化的生毛体略呈球状,球状体的中央由一团染色深的颗粒状物质构成,外围分化出若干柱状体.已分化的生毛体由柱状体分散或辐射状排列构成,呈球状,球体中心不含染色深的物质.多层结构位于精子细胞内的基体和巨大线粒体之间,刚形成时仅由片层构成,片层相互平行排列形成片层带.多层结构在分化中期由微管带、片层带和蚀斑三层构成.多层结构在分化末期又形成附属微管带、嗜锇冠和嗜锇层.微管带从多层结构长出,沿细胞核的表面伸展,并与核膜之间形成复合结构.基体由柱状体转变而成,它向两端生长,在远端产生鞭毛的轴丝,在近轴端形成楔状结构.本文首次详细阐明了原始薄囊蕨分株紫萁生毛体和多层结构发育的超微结构特点,并与其他蕨类进行了比较,发现其片层带出现在微管带形成之前.     

Ultrastructure of the differentiating zygotospores of Porphyra leucosticta (Rhodophyta)

The ultrastructure of zygotosporogenesis is described for the red alga Porphyra leucosticta Thuret. Packets of eight zygotosporangia, each packet derived from a single carpogonium are interspersed among vegetative cells. Zygotospore differentiation in Porphyra can be separated into three developmental stages. (i) Young zygotospores exhibit a nucleus and a large centrally located, lobed plastid with pyrenoid. Mucilage is produced within concentric membrane structures during their dilation, thus resulting in the formation of mucilage sacs. Subsequently, these sacs release their contents, initiating the zygotospore wall formation. Straight‐profiled dictyosomes produce vesicles that also provide wall material. During the later stages of young zygotospores, starch polymerization commences, (ii) Medium‐aged zygotospores are characterized by the presence of fibrous vacuoles. These are formed from the ‘fibrous vacuole associated organelles’. The fibrous vacuoles finally discharge their contents. (iii) Mature zygotospores are recognized by the presence of numerous cored vesicles produced by dictyosomes. Cored vesicles either discharge their contents or are incorporated into the fibrous vacuoles. There is a gradual reduction of starch granules during zygotospore differentiation. Mature zygotospores are surrounded by a fibrous wall, have a large chloroplast with pyrenoid and well‐depicted phycobilisomes but are devoid of starch granules.     

Evidence for the introduction of the Asian red alga Neosiphonia japonica and its introgression with Neosiphonia harveyi (Ceramiales,Rhodophyta) in the Northwest Atlantic

There is currently conflict in the literature on the taxonomic status of the reportedly cosmopolitan species Neosiphonia harveyi, a common red alga along the coast of Atlantic Canada and New England, USA. Neosiphonia harveyi sensu lato was assessed using three molecular markers: COI‐5P, ITS and rbcL. All three markers clearly delimited three genetic species groups within N. harveyi sensu lato in this region, which we identified as N. harveyi, N. japonica and Polysiphonia akkeshiensis (here resurrected from synonymy with N. japonica). Although Neosiphonia harveyi is considered by some authors to be introduced to the Atlantic from the western Pacific, it was only confirmed from the North Atlantic suggesting it is native to this area. In contrast, Neosiphonia japonica was collected from only two sites in Rhode Island, USA, as well as from its reported native range in Asia (South Korea), which when combined with data in GenBank indicates that this species was introduced to the Northwest Atlantic. The GenBank data further indicate that N. japonica was also introduced to North Carolina, Spain, Australia and New Zealand. Despite the fact that all three markers clearly delimited N. harveyi and N. japonica as distinct genetic species groups, the ITS sequences for some N. harveyi individuals displayed mixed patterns and additivity indicating introgression of nuclear DNA from N. japonica into N. harveyi in the Northwest Atlantic. Introgression of DNA from an introduced species to a native species (i.e. ‘genetic pollution’) is one of the possible consequences of species introductions, and we believe this is the first documented evidence for this phenomenon in red algae.     

Ultrastructure of auxiliary and gonimoblast cells during carposporophyte development in the red alga Cryptopleura ruprechtiana (Delesseriaceae, Ceramiales, Rhodophyta)

The ultrastructure sequence for the complete post-fertilization development is described in Cryptopleura ruprechtiana (C. Agardh) Kylin, a member of the Delesseriaceae. Following fertilization the diploid nucleus is transferred to the auxiliary cell. This contains typical red algal proplastids, cytoplasmic concentric membranes, numerous small vacuoles and lipid bodies. Crystalline inclusions and virus-like particles are also present. In addition darkly staining spherical masses possibly represent dehydrated haploid chromatin. The multinucleate auxiliary cell produces initially one large gonimoblast initial and subsequently many smaller gonimoblast initials. The first formed generative gonimoblast cell is similar in cellular structure to the auxiliary cell. Gonimoblast initials are uninucleate but through caryokinesis they become multinucleate. They undergo repeated cleavage to form more gonimoblast cells. Subsequent, centripetal cytokinesis results in the formation of clusters of gonimoblast cells. A new type structural cap or association is observed in the septal plugs that interconnect gonimoblast initials. Terminal or generative gonimoblast cells cleave to form additional gonimoblast cells. Only terminal gonimoblast cells are differentiated to carpospores.