Laurencia majuscula var. elegans (Rhodophyta,Rhodomelaceae) is reinstated to specific rank as L. elegans

Laurencia majuscula has recently been determined to be conspecific with Laurencia dendroidea. To determine the correct taxonomic placement of its only non‐typical variety, L. majuscula var. elegans, mitochondrial COI‐5P and chloroplast rbcL gene sequences were analyzed and its phylogenetic position was inferred. Laurencia majuscula var. elegans consistently formed a well‐supported clade distinctly separate from the L. dendroidea clade. Molecular analyses revealed that L. majuscula var. elegans generally shows two distinct forms; a long‐branched form, and a compact form. Often the compact form has been identified as a different species based on morphology alone. Included in these analyses were topotype sequences of two species with which L. majuscula var. elegans is most often misidentified; Laurencia nidifica and Laurencia mcdermidiae. Laurencia nidifica formed a well‐supported clade separate from L. majuscula var. elegans. Laurencia mcdermidiae, however, formed a well‐defined clade sister to the L. majuscula var. elegans clade. Morphological comparisons were also made. It is concluded that L. majuscula var. elegans is morphologically distinct from L. dendroidea, L. nidifica, and L. mcdermidiae. It is proposed that L. majuscula var. elegans be reinstated to species level as L. elegans.     

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 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.     

Taxonomic notes on Hawaiian Polysiphonia, with transfer to Neosiphonia (Rhodomelaceae, Rhodophyta)

After detailed observations of type material and other collections, five Hawaiian species of Polysiphonia Greville, nom. cons. are recognized to be species of Neosiphonia M. S. Kim et I. K. Lee; namely, Neosiphonia apiculata (Hollenberg) Masuda et Kogame, Neosiphonia beaudettei (Hollenberg) M. S. Kim et Abbott, comb. nov., Neosiphonia hawaiiensis (Hollenberg) M. S. Kim et Abbott, comb. nov., Neosiphonia profunda (Hollenberg) M. S. Kim et Abbott, comb. nov., and Neosiphonia rubrorhiza (Hollenberg) M. S. Kim et Abbott, comb. nov. These five species are ecorticate, having lateral branch initials and trichoblasts produced on successive segments, rhizoids separated from pericentral cells by a cross wall, three‐celled carpogonial branches (not seen in N. beaudettei and N. rubrorhiza), spermatangial branches arising on a primary branch of the trichoblasts, and tetrasporangia in a spiral series. Although certain characters were not available for some species, all other characters occur in a combination that is unique for members of Neosiphonia.     

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.     

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.     

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.     

Molecular relationships within Bostrychia tenuissima (Rhodomelaceae, Rhodophyta)

Bostrychia tenuissima King and Puttock is restricted to southern Australia and New Zealand. Previous studies in Australia have revealed two distinct patterns in the presence of osmotically active polyols. Southern populations only have D-sorbitol whereas northern populations have both D-sorbitol and D-dulcitol. These polyol patterns lead to speculation on the ecotypic differentiation of these two population types. Using single-stranded confirmation polymorphism to rapidly score plastid haplotypes, plus DNA sequencing, a 100% congruence was found between polyol patterns and plastid haplotype. Analysis of 33 B. tenuissima isolates shows that the plastid relationships closely follow biogeo-graphic regions, with south-eastern Australia (southern NSW and Victoria) and South Australia and Tasmania having one haplotype and central and northern NSW having two alternate haplotypes. There is an overlap at the haplotype boundary just south of Sydney, New South Wales.     

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.     

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.     

A new species of Laurencia, L. omaezakiana (Ceramiales, Rhodophyta), from Japan

Laurencia omaezakiana Masuda, sp. nov. (Ceramiales, Rhodophyta) is described from Japan. It is characterized by the following set of features: (i) the production of four periaxial cells from each vegetative axial cell; (ii) a shift in branching from distichous to spiral; (iii) the presence of projecting superficial cortical cells near the apices of branches; (iv) the presence of longitudinally oriented secondary pit-connections between contiguous superficial cortical cells; (v) the presence of lenticular thickenings in the walls of medullary cells; (vi) the occurrence of 1–2 corps en cerise in each superficial cortical cell and a single corps en cerise in each trichoblast cell; and (vii) a parallel arrangement of tetrasporangia. Furthermore, it produces a characteristic triterpenoid (enshuol), which has not been detected in other species of Laurencia, as a major halogenated secondary metabolite. A synoptical key to the 23 species of Laurencia growing in Japan is given. Laurencia ceytanica J, Agardh and Laurencia heteroclada Harvey are excluded from the Japanese marine algalflora. The latter is a distinct species from Laurencia filiformis (C. Agardh) Montagne.     

Transfer of Pterosiphonia pumila Yendo to the genus Symphyocladia (Rhodomelaceae, Rhodophyta)

The red alga Pterosiphonia pumila Yendo (Rhodomelaceae, Ceramiales) has flattened thalli in which there is complete lateral fusion between branches and their parental axes during early stages of development, the laterals only becoming distally free in reproduc-tively mature plants. This results in a leaf-like organization distinct from that displayed by all other species of the genus Pterosiphonia, the members of which have terete to compressed axes that are congenitally fused along only a few (<4.5) proximal segments of the laterals. The organization of P. pumila is, thus, similar to that of species of the genus Symphyocladia, to which it is here transferred as Symphyoctadia pumila (Yendo) Uwai et Masuda, comb. nov. Symphyoctadia pumila is restricted to Japan and Korea and is distinguished from the other three described species of Symphyocladia by its small (<3 cm long) ecorticate thalli and complete lack of vegetative trichoblasts. Symphyoctadia pennata Okamura has a similar suite of characteristics, has been successfully cross-bred with S. pumila in laboratory culture and is, thus, placed in synonymy with S. pumila.     

Hybridization studies in Bostrychia. 1: B. radicans (Rhodomelaceae, Rhodophyta) from Pacific and Atlantic North America

Bostrychia radicans(Montagne) Montagne is a pantropical/temperate red alga associated with mangroves and saltmarsh plants. Collections were made from a similar north-south geographic distribution along both the Pacific and Atlantic coasts of North America. Hybridization studies were performed with cultured isolates to assess the extent of interfertility and reproductive isolation along these two coastlines. All male and female gametophytes derived from single tetrasporophytes were intercompatible. Almost all isolates extending over 1500 km of coast line from northern Pacific Mexico are compatible, forming cystocarps that released viable carpospores. Even isolates which morphologically would be placed in two species [B. radicans and B. moritziana(Sender ex Kützing) J. Agardh], based on the presence or absence of monosiphonous branches, were capable of hybridizing. Crosses of isolates from the Atlantic USA showed a greater amount of incompatibility. Certain isolates were not compatible with any other isolates including isolates collected in close proximity (North Carolina isolates), while other isolates from the same locality were compatible (South Carolina). An isolate from South Carolina formed tetrasporophytes with isolates from Pacific Mexico but tetraspores were not viable. Certain incompatible crosses formed ‘pseudocystocarps’ but viable carposporophytes did not develop. Generalizations about reproductive isolation within a species must also consider differences between populations from different biogeographic regions that may reflect different paleoclimatological histories, founder effects and unique dispersal events.     

C(15) Acetogenins from the red alga Laurencia obtusa.

Four C(15) acetogenins, 13-epilaurencienyne (3Z) (1), 13-epipinnatifidenyne (3E) (2), (3E, 6S(*), 7R(*), 9S(*), 10S(*), 12R(*))-9-chloro-13-bromo-6:12-epoxy-7, 10-diacetoxypentadec-3-en-1-yne (3), (3Z, 6S(*), 7R(*), 9S(*), 10S(*), 12R(*))-9-chloro-13-bromo-6:12-epoxy-7, 10-diacetoxypentadec-3-en-1-yne (4), along with the known 13-epilaurencienyne (3E) (5), have been isolated from the organic extract of the red alga Laurencia obtusa, collected in the Aegean Sea, Greece. The structures of the new natural products, as well as their relative stereochemistry, were established by means of spectral data analysis, including 2D NMR spectroscopic experiments. Some of the new metabolites exhibited significant insecticidal activity.     

Growth and the content of laurinterol and debromolaurinterol in Laurencia okamurae (Ceramiales, Rhodophyta)

The growth of Laurencia okamurae and the content of laurinterol and debromolaurinterol were influenced by various factors. Temperature influenced growth raere te with a maximum at 25°C, regardless of daylength. Maturity depended on temperature rather than daylength; the plants grew without maturing at 15°C, while the plants matured within two weeks at 25°C. The plants were able to grow at salinities of 14–50‰ with maximum growth at 26‰. The salinities growth rash;50‰te reduced with decreasing concentration of nitrate below 1.2 × 10^-3 M, and of total phosphate below 7.5× 10^-8 M. Bromide concentration had no effect on growth, and the plants grew without bromide. Variation in temperature between 15–25°C and daylength produced no obvious change in laurinterol and debromolaurinterol contents. On the other hand, an increase in salinity led to an increase for both. The plants cultured in a completely artificial medium, modified ASP₁₂NTA, showed a marked drop in their content of these metabolites. An increase in concentrations of nitrate, total phosphate or bromide did not restore the content. This revised version was published online in June 2006 with corrections to the Cover Date.