Michio Masuda

MORPHOLOGY AND HALOGENATED SECONDARY METABOLITES OF THREE GRAN CANARIAN SPECIES OF LAURENCIA (CERAMIALES, RHODOPHYTA)

Laurenda majuscula (Harvey) Lucas is characterised by the production of four periaxial cells from each vegetative axial segment and of two tetrasporangium-bearing (the third and fourth) periaxial cells per fertile segment in tetrasporangial branches, in addition to other features. Major halogenated secondary metabolites of this species are sesquiterpenoids, isoobtusol and elatol. Laurenda intricata Lamouroux is characterised by the presence of 2-4 corps en cerise per superficial cortical cell, in addition to other features. A major halogenated compound of this alga is a sesquiterpenoid, caespitol. Laurenda perforata (Bory) Montagne is characterised by the production of two periaxial cells from each vegetative axial segment, tetrasporangia formed on two (the second and additional third) periaxial cells from each axial segment in tetrasporangial branches, and the absence of corps en cerise, in addition to other features. Halogenated secondary metabolites were not detected in this alga, although some characteristic sesquiterpenoids have been reported from material collected from Fuerteventura, the Canary Islands. This strongly suggests that the Fuerteventuran alga was not properly identified.

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.

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.

Anhydroaplysiadiol from laurencia japonensis

Abstract A new brominated, anhydroaplysiadiol has been isolated from a new Laurencia species, L. japonensis Abe et Masuda sp. ined., along with aplysiadiol and 2,10-dibromo-3-chloro- α -chamigrene. The last two compounds are commonly found in this species collected from various localities. The structure of anhydroaplysiadiol was deduced from spectral evidence.

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.

Laurencia japonensis sp. nov. (Ceramiales, Rhodophyta)

The marine red alga Laurencia japonensis sp. nov. (Rhodomelaceae, Ceramiales) is described from the warm temperate region of Japan. It is characterized by the following combination of features: (1) terete, rigidly cartilaginous, upright axes arising from a primary discoid holdfast and stolon-like branches; (2) tristichous branching; (3) penultimate and ultimate branches showing pronounced adaxial bending; (4) adventitious branches formed chiefly in the axils; (5) the production of four periaxial cells per vegetative axial segment; (6) the presence of longitudinally oriented secondary pit connections between contiguous superficial cortical cells; (7) the absence of projecting superficial cortical cells; (8) the absence of a radially elongated cortical layer; (9) the presence of abundant lenticular thickenings in the walls of medullary cells; (10) the presence of a single corps en cerise per superficial cortical cell and trichoblast cell; (11) a parallel arrangement of tetrasporangia; (12) broadly ovoid cys...

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.

A Morphological Study of Laurencia palisada (Rhodomelaceae, Rhodophyta)

The red alga Laurenda palisada Yamada (Rhodomelaceae, Ceramiales), the lectotype species of the section Palisadae, is characterised by the following set of features: 1) rigidly cartilaginous upright axes arising from a discoid holdfast; 2) a shift of branching from a distichous to a spiral manner distally; 3) the production of two periaxial cells per vegetative axial segment; 4) the absence of longitudinally oriented secondary pitconnections between cintiguous superficial cortical cells; 5) the absence of projecting superficial cortical cells; 6) the presence of a palisade-like cortical layer; 7) the absence of lenticular thickenings in the walls of medullary cells; 8) the absence of corps en cerise in any cell; 9) the production of two tetrasporangium-bearing periaxial cells from each fertile segment; 10) a perpendicular arrangement of tetrasporangia; 11) procarps produced from the last-formed (fourth) peraxial cell of the terminal segment of a two-celled female trichoblast; 12) flask-shaped cystocarps; and 13) distally positioned spermatangial nuclei.

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.

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.