Sesquiterpenoids of Laurencia majuscula (Ceramiales, Rhodophyta) from the Ryukyu Islands, Japan

Two populations of the red alga Laurencia majuscula (Harvey) Lucas (Rhodomelaceae, Ceramiales) from Taketomi Island and Hateruma Island, the Ryukyu Islands, Japan, have been characterized on the basis of both morphological features and halogenated secondary metabolite content. These populations have smaller and more slender thalli than those of other regions. Furthermore, the populations contain two chamigrane-type Sesquiterpenoids, (2R, 3R, 5S)-5-acetoxy-2-bromo-3-chlorochamigra-7(14),9-dien-8-one and (2R, 3R)-2-bromo-3-chlorochamigra-7(14), 9-dien-8-one, and a laurane-type sesquiterpenoid, debromoisolaurinterol, as secondary metabolites which are different from those previously reported from other populations. These results are consistent with the concept of ‘chemical races’ within a single species of Laurencia.     

Taxonomic notes on Laurencia mariannensis (Rhodomelaceae, Rhodophyta)

The marine red alga Laurencia mariannensis Yamada (Rhodomelaceae, Ceramiales) is characterized by pale rose-red, softly fleshy, slender, terete axes (up to 600 μm in diameter), arising from a loosely entangled, stoloniferous basal system among species that have the following combination of features: the presence of longitudinally orientated secondary pit-connections between contiguous superficial cortical cells; the presence of projecting superficial cortical cells at the upper portions of branches; and the presence of lenticular thickenings in the walls of medullary cells, Furthermore, the presence of two or three corps en cerise per superficial cortical cell and one per trichoblast cell may characterize the species.     

Taxonomic notes on Laurencia brongniartii (Rhodomelaceae, Rhodophyta)

The red alga Laurencia brongniartii J. Agardh (Rhodomelaceae, Ceramiales) is characterized by: (i) the production of four periaxial cells from each vegetative axial segment; (ii) the presence of two or three corps en cerise per superficial cortical cell and one per trichoblast cell; (iii) the production of a single tetrasporangium-bearing periaxial (fourth) cell per fertile segment; (iv) a tetrasporangial arrangement that is intermediate between perpendicular and parallel types; (v) procarps produced from the last-formed (fifth) periaxial cell of the terminal segment of a two-celled female trichoblast; and (vi) distally positioned spermatangial nuclei, in addition to known features. The production of a single tet-rasporangium-bearing periaxial cell per fertile segment allies this species to Laurencia similis Nam et Saito.     

Additional analysis of chemical diversity in Laurencia nipponica (Ceramiales, Rhodophyta)

The red alga Laurencia nipponica Yamada (Rhodomelaceae, Ceramiales) is known to contain several chemical races, each of which is characterized by a particular, major halogenated secondary metabolite. Both field-collected and cultured plants of a population of this species found recently at Shikanoshima Island, Fukuoka Prefecture, southern Japan, produced C₁₅ bromoethers, (3E)-laureatin and (3E)-isolaureatin, and sesquiterpenoids, 2,10-dibromo-3-chloro-9-hydroxy-α-chamigrene and 2,10-dibromo-3-chloro-α-chamigrene. Laurencia nipponica can be referred to as a further chemical race that is characterized by the production of two C₁₅ bromoethers, (3E)-laureatin and (3E)-isolaureatin, and a sesquiterpenoid, 2,10-dibromo-3-chloro-9-hydroxy-α-chamigrene as major compounds.     

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.     

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.     

Additional analysis of chemical diversity of the red algal genus Laurencia (Rhodomelaceae) from Japan

The halogenated secondary metabolite constitution of four species of the red algal genus Laurencia (Rhodomelaceae) from southern Japan is reported. Laurencia composita Yamada from Tanegashima Island (Kagoshima Prefecture) bears five sesquiterpenoids (2,10‐dibromo‐3‐chloro‐α‐chamigrene and 2,10‐dibromo‐3‐chloro‐9‐hydroxy‐α‐chamigrene, in addition to pre‐pacifenol epoxide, johnstonol and pacifenol, which are known in other populations of this species). Laurencia intricata Lamouroux from Chinzei (Saga Prefecture) and Oomura Bay (Nagasaki Prefecture) bear a C₁₅ aceto‐genin, okamurallene. Laurencia majuscula (Harvey) Lucas from Tanegashima Island produces three sesquiterpenoids, (Z)‐10,15‐dibromo‐9‐hydroxy‐chamigra‐1, 3(15),7(14)‐triene, 10‐bromo‐7‐hydroxylaurene and 10,11‐dibromo‐7‐hydroxylaurene, corresponding to those of one of its chemical races. Laurencia venusta Yamada from Tanegashima Island produces two sesquiterpenoids, cupalaurenol and cyclolaurenol, which were known only from a sea hare, Aplysia dactylomela Rang. This strongly suggests that Aplysia consumes L. venusta and concentrates these halogenated compounds.     

Neorhodomela enomotoi sp. nov. (Ceramiales, Rhodophyta) from Japan

The red alga Neorhodomela enomotoi Masuda et Kogame (Rhodomelaceae, Ceramiales) is described as a new species from Japan. It is characterized by the following combination of features: (i) thalli reddish-brown and slightly rigid; (ii) first-order branches mostly indeterminately branched; (iii) adventitious branches infrequent, determinately branched and formed chiefly in the axils of lateral branches; (iv) vegetative trichoblasts abundant; (v) tetrasporangia produced on paniculate ultimate and penultimate branches; and (vi) cystocarps flask-shaped (urceolate). This species has been found growing only in the upper subtidal zone in the warm temperate waters of Japan.     

Morphology of Laurencia clavata and L. elata (Ceramiales,Rhodophyta) in relation to generic circumscription in the Laurencia complex

Laurencia Lamouroux (Rhodophyta) was recently separated into three genera–Laurencia, Chondrophycus (Tokida et Saito) Garbary et Harper and Osmundea Stackhouse – each of which was newly defined based on vegetative and reproductive structures. In this study, the previously unknown vegetative and reproductive morphology of two Australian endemic species of Laurencia, L. clavata Sonder and L. elata (C. Agardh) Harvey, was studied, particularly in the context of the revised generic delineation. These species exhibit vegetative axes with four pericentral cells and trichoblast-type spermatangial development. Tetrasporangia are abaxially produced from the existing third and fourth pericentral cells. L. clavata has terete thalli with distinctive verticillate branching and is similar to Chondria C. Agardh, rather than to Laurencia, in having an unusually marked constriction at the base of the branches and starch accumulation in subcortical and medullary cells. Compared to Laurencia, apical cells of this species exhibit a less oblique division ; the resulting recognizable axial cell rows extend somewhat below the branches, and particularly at a young stage they are also clear throughout branchlets. However, other vegetative and spermatangial structures show that L. clavata is more closely allied to Laurencia than to Chondria, and it is placed in Laurencia. By contrast, L. elata exhibits morphology typical of Laurencia and is characterized by large, robust, compressed thalli with fastigiately distichous branching and an extensive secondary cortex. Furthermore, it appears to be distinct from similar species in sometimes having a parasitic species of Janczewskia Solms-Laubach (Rhodophyta). Taxonomy of Laurencia is discussed on the basis of these and previous studies.     

Agar from the red seaweed,Laurencia flexilis (Ceramiales,Rhodophyta) from northern Philippines

The worldwide production of the gelling agent agar mainly rely on the red algae of the order Gracilariales and Gelidiales for raw material. We investigate here the potential of a species from another red algal order, Ceramiales as an agar source. The agar from Laurencia flexilis collected in northern Philippines was extracted using native and alkali treatment procedures and the properties of the extracts were determined using chemical, spectroscopic and physical methods. The native agar, 26% dry weight basis, forms a gel with moderate gel strength (200 g cm^?2). Alkali‐treatment did not enhance the gel strength, indicating insignificant amounts of galactose‐6‐sulfate residue, the precursor of the gel‐forming 3,6‐anhydrogalactose (3,6‐AG) moieties. Furthermore, the Fourier transform infrared and chemical analysis showed low sulfate and high 3,6‐AG levels, not affected significantly by the alkali treatment. Nuclear magnetic resonance spectroscopic analysis revealed 3‐linked 6‐O‐methyl‐D‐galactose and 4‐linked 3,6‐anhydro‐L‐galactose as the major repeating unit of the native extract, with minor sulfation at 4‐position of the 3‐linked galactose residues. The native and alkali treated agars have comparably high gelling and melting temperatures, whereas the former exhibits higher gel syneresis. Laurencia flexilis could be a good source of agar that possesses physico‐chemical and rheological qualities appropriate for food applications. Due to the inability of alkali treatment to enhance the key gel qualities of the native extract, it is recommended that commercial agar extraction from this seaweed would be done without pursuing this widely‐used industrial procedure.     

The morphology and taxonomy of Womersleya monanthos, an endemic species and genus of Delesseriaceae (Ceramiales, Rhodophyta) from southeastern Australia

Womersleya monanthos (J. Agardh) Papenfuss is typically an epiphyte of larger brown and red algae that are common in drift along the southeastern coasts of Australia. A hitherto little-known member of the Phycodrys group of the Nitophylloideae, its reproductive features have been studied in detail and its taxonomic position clarified. Blades are polystromatic throughout and lack veins or nerves, with blades originating from apical cells of primary and second-order cell rows. Intercalary cell divisions take place in primary cell rows and all other branch orders, with third-order laterals arising both abaxially and adaxially on cells of second-order rows. Fertile central cells bear procarps on pericentral cells on both sides of the blade, the procarps consisting of two 4-celled carpogonial branches and a single central group of sterile cells that enlarge and persist at the distal end of a bicampanulate fusion cell at maturity. Spermatangia and tetrasporangia form in circular subapical sori on both sides of the blade or in marginal lobes or proliferations. After comparing it to other members of the Phycodrys group, we conclude that Womersleya is a monotypic genus well distinguished from other genera and with probable closest affinities to the Northern Hemisphere Polyneura, Erythroglossum and Sorella, as well as the Australian endemic, Crassilingua.     

Habitat characteristics and seasonal changes of Laurencia brongniartii (CeramiaIes, Rhodophyta) in Kagoshima, Southern Japan

The seasonal change in size of Laurencia brongniartii was observed for the year 2002 at Banshobana Park, Satsuma Peninsula and Tsuchihama Beach, Amami Oshima, both in Kagoshima Prefecture, Japan. Additionally, the vertical distribution of this species was also studied at Tsuchihama Beach (second site), where the largest populations were found. Maximum lengths were observed in October ‐ November with a size of 100 ± 6 mm at Banshobana Park and 111 ± 5 mm at Tsuchihama Beach. Line‐transects conducted at Tsuchihama Beach, were analyzed to determine the vertical distribution of L. brongniartii due to depth and the slope of the substrate. Alga was found growing in areas restricted to low levels of light.     

Developmental morphology of Odonthalia floccosa (Ceramiales, Rhodophyta) in laboratory culture

Material of the red alga Odonthalia floccosa (Esper) Fal-kenberg (Rhodomelaceae, Ceramiales), collected from California, was cultured in the laboratory and its life-history was completed. Tetraspores grew into bipolar sporelings that differentiated into a colorless rhizoidal portion and a pigmented upright shoot. The sporelings became compressed apically and formed lateral branches in a regularly distichous manner that were congenitally fused with the main axis. These tetraspore germlings grew into diecious gametophytes. Male ga-metophytes produced numerous spermatangia on modified fertile branchlets (male trichoblasts) that possessed three to four monosiphonous, proximal segments. Female gametophytes formed a single pro-carp on the suprabasal segment of unbranched female trichoblasts. Cystocarps developed on the female gametophytes cocultured with male gametophytes and released viable carpospores that developed into fertile te-trasporophytes. Tetrasporangia were produced from the third and fourth periaxial cells in each of 12–45 successive fertile segments and provided three (two lateral and one basal) cover cells. The occurrence of both spermatangia and procarps on fertile trichoblasts in O. floccosa suggests that the alga is the most derived in these two characters among the species of the genus Odonthalia. This species is distributed in cold temperate regions in the North Pacific, and it should be excluded from the North Atlantic marine algal flora.     

Taxonomic notes on three species of Herposiphonia (Ceramiales, Rhodophyta) found in Japan

Three species of the red algal genus Herposiphonia (Ceramiales, Rhodomelaceae) found in Japan are described, and taxonomic features of the genus are discussed. Herposiphonia crassa Hollenberg is reported from Japan for the first time and is characterized by thick axes (200–350 µm in diameter) and determinate branches (100–200 µm in diameter), relatively short determinate laterals (400–1200 µm in length) with a large number of periaxial cells (15–19 per segment) and three (occasionally two or four) vigorously developed (1.8–2.5 mm in length by 50–75 µm in diameter basally) trichoblasts on each determinate lateral. Herposiphonia elongata Masuda et Kogame is also reported from Japan for the first time and is characterized by the conspicuous thickening growth of cystocarp‐bearing branches and spermatangial branches with an elongated sterile tip. Some newly found features of Herposiphonia fissidentoides (Holmes) Okamura are presented: the rhizoid production from the central portion of parental periaxial cells in addition to the distal end, virtual absence of vegetative trichoblasts, production of procarpial trichoblasts and spermatangial branches on fertile determinate branches on short indeterminate laterals, cystocarps sometimes with a short spur, and extremely large tetrasporangia.     

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.     

Australian Laurencia majuscula (Rhodophyta,Rhodomelaceae) and the Brazilian Laurencia dendroidea are conspecific

Morphological and molecular studies have been undertaken on two species of the red algal genus Laurencia J.V.Lamouroux: Laurencia majuscula (Harvey) A.H.S. Lucas and Laurencia dendroidea J.Agardh, both from their type localities. The phylogenetic position of these species was inferred by analysis of the chloroplast‐encoded rbcL gene sequences from 24 taxa. In all phylogenetic analyses, the Australian Laurencia majuscula and the Brazilian L. dendroidea formed a well‐supported monophyletic clade within the Laurencia sensu stricto. This clade was divided into two subclades corresponding to each geographical region; however, the genetic divergence between Australian L. majuscula and Brazilian L. dendroidea was only 0–1.35%. Examination of the type specimens and sequences of freshly collected samples of both Laurencia majuscula and L. dendroidea show the two to be conspecific despite their disjunct type localities.     

Dasya enomotoi sp. nov. (Dasyaceae,Ceramiales), a new large Dasya from Japan

A new red alga, Dasya enomotoi, is described from Japan. This species is characterized by having a large thallus consisting of an elongated axis and many, radially arranged, polysiphonous branches both of which are heavily corticated and densely covered with numerous, soft monosiphonous filaments. It is distinguished from several similar species by the combination of the following: (i) indistinct pericentral cells in transverse sections except near the apices, (ii) the presence of enlarged, inner cortical cells, (iii) radially arranged adventitious monosiphonous filaments, (iv) three‐celled carpogonial branches, (v) six (sometimes five) tetrasporangia in each fertile segment of the stichidia, and (vi) three tetrasporangial cover cells that are not elongated longitudinally and usually not divided transversely. This species may have been identified as D. villosa Harvey by previous investigators in Japan.     

Two species of Dasya (Ceramiales, Rhodophyta) from Bonin Islands, southern Japan, with the description of Dasya boninensis sp. nov.

Two species of Dasya in the Dasyaceae (Ceramiales, Rhodophyta) are reported from Bonin Islands, southern Japan. Dasya murrayana Abbott et Millar, new to Japan, is characterized by the following set of features: the tufted habit (up to 30 erect axes developing from a basal disc), small‐sized (6–10 mm high and 350–500 μm in diameter in the middle region), thinly but completely corticated axes, rigid and incurved pseudolaterals forming corymbose heads at the apices of axes and branches, the absence of adventitious monosiphonous filaments, a large number of tetrasporangial stichidia and spermatangial branches per fertile pseudolateral and slender spermatangial branches (35–45 μm in diameter). Dasya boninensis Masuda, Kurihara et Kogame, sp. nov. is characterized by short but thick (10–30 mm high and 600–1000 μm in diameter at the middle portion), heavily corticated axes, indistinct pericentral cells except for the upper portion in transverse sections, soft, straight pseudolaterals and adventitious monosiphonous filaments densely covering the axis and branches, a small number of tetrasporangial stichidia and spermatangial branches per fertile pseudolateral, thick spermatangial branches (65–90 μm in diameter), and short‐necked cystocarps. A dichotomous key to the taxa found in Japanese waters is given.     

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.