Morphological and taxonomic studies on some little-known species of Gracilaria (Gracilariales: Rhodophyta) from Venezuela. 1. G. damaecornis

The morphology, anatomy and reproduction (tetrasporic, male and female) of a poorly known species of Gracilaria i.e. G. damaecornis J. Agardh was studied, using material collected in eastern Venezuela. Spermatangia are produced in well-defined and deeply immersed multicavitied conceptacles (m type). Nutritive filaments are present both at the floor and top (outer pericarp) of the cystocarp. The lectotype of G. damaecornis is illustrated for the first time. Hydropuntia albornozii (Rodríguez) Wynne (Polycavernosa albornozzi) is shown to be a synonym of G. damaecornis. In agreement with recent research, it is concluded that generic attributes of Hydropuntia ( = Polycavernosa) based on mainly on sexual reproductive structures are of doubtful taxonomic value.     

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 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.     

Apical callus formation in Solieria filiformis (Gigartinales,Rhodophyta) cultured in tanks

Loose-lying wild plants of the carragenophyte Solieria filiformis (Kützing) Gabrielson were cultivated under greenhouse conditions in 600 l tanks in stationary and turbulent cultures, produced either by air bubbling or water jets at the bottom of the tanks. One week after inoculation 90.3% of the apices of the plants grown in air turbulent cultures initiated the formation of callus. The apices were not broken and apparently non-wounded. No callus formation were observed from a few accidentaly broken apices in any culture. Only 4% of the apices in water turbulent cultures induced callus. Reorganization of branches from the calli took place after three weeks. Organogenetic calli detached from the mother plant after four weeks and formed spherical masses of 3 cm in diameter growing as unattached balls. Cellular disorganization (i.e. callus formation) in S. filiformis seems to be a consequence of intermittent abrasion or contact stimuli against tank walls produced by turbulence.     

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.     

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.     

Diagnoses and key to the genera of the Gracilariaceae (Gracilariales,Rhodophyta)

A key to the genera of the Gracilariaceae is provided along with a short diagnosis for each genus. Features of the mature cystocarp and spermatangial configurations that separate genera are illustrated.     

Growth of the conchocelis phase of Porphyra columbina (Bangiales, Rhodophyta) at different temperatures and levels of light, nitrogen and phosphorus

Temperature, light, nitrogen and phosphorus all had significant effects on the growth of conchocelis colonies of Porphyra columbina Montagne when grown in vitro using a shell substrate. High rates of growth were recorded at 15°C and at 8°C under low light levels. These fight and temperature conditions are similar to those found in the subtidal environment of southern New Zealand coastlines. Little growth occured at 22°C. Nitrogen stimulated growth at concentrations far greater than are likely to be found in situ, while at concentrations of 120 μmol/L and above phosphorus had an inhibitory effect on growth, The culture parameters were strongly interactive in their effect on growth, in particular temperature and light. Conchosporangia formed in all treatments 14 days after alteration of the photoperiod to 10 h light: 14 h dark. Optimal conditions for culture of the conchocelis of P. columbina from southern New Zealand are a water temperature of approximately 15°C, light levels between 10 and 50 μmol m^?2s^?1 and seawater nitrogen levels maintained above 100 μmol/L.     

A new crustose red alga Peyssonnelia rumoiana (Rhodophyta, Gigartinales) from Japan

The marine red alga Peyssonnelia rumoiana Kato et Masuda, sp. nov. (Peyssonneliaceae, Gigartinales) is described from warm‐ and cold‐temperate regions in Japan. It is principally characterized by having hypo‐thallial filaments comprising a polyflabelate layer, proximal perithallial cells arising from the whole upper surface of each hypothallial cell (Peyssonnelia rubra‐type anatomy) and closely packed in a firm matrix, the production of two filaments from the proximal perithallial cell, unicellular rhizoids, appressed crust margins and hypobasal calcification. The alga is distinguished from related species by: (i) its conspicuously elevated cystocarpic (100–150 μm high) and tetrasporangial (80–110 μm high) nemathecia; (ii) tetrasporangia with or without a unicellular pedicel; and (iii) large (25–45 μm in diameter by 70–115 μm in length) tetrasporangia and (iv) the production of double chains of spermatangia (Peyssonnelia harveyana‐type spermatangial development).     

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.     

A morphological and molecular assessment of the genus Sinotubimorpha (Halymeniaceae, Rhodophyta)

A critical reassessment of the morphological features of two closely related red algal genera,Grateloupia C.Agardh and Sinotubimorpha W.X.Li & Z.F.Ding (Halymeniaceae),pointed out that members of the t...     

Reinstatement of Grateloupia subpectinata (Rhodophyta, Halymeniaceae) based on morphology and rbcL sequences

Morphological observations and molecular analyses of the north‐western Pacific species of the red algal genus Grateloupia (Halymeniaceae) indicate the presence of an entity, which is somewhat similar in gross morphology to G. asiatica Kawaguchi et Wang but is distinguished from the latter species by some morphological features. These include: (i) a somewhat fleshy texture; (ii) wider and much thicker (4.5–10 mm wide and up to 1300 μm thick) axes, of which an inner cortex consists of more (6–9) cells; (iii) generally longer (up to 17 cm), marginal and surface proliferations that are clearly constricted (terete) at bases; and (iv) much elongated, oblong auxiliary cells. Phylogenetic analysis using the ribulose‐l,5‐bisphosphate carboxylase/ oxygenase (rbcL) gene of G. asiatica and the alga in question shows them to be distantly related and strongly supports the differentiation of these two entities at the species level. Judging from the literature, this entity is actually Grateloupia subpectinata Holmes, which has been placed into synonymy under G. asiatica [as G. filicina (Lamouroux) C. Agardh] or G. prolongata J. Agardh in previous reports, and therefore the Holmes name is reinstated.     

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.     

Effects of plant growth substances on the conchocelis phase of Alaskan Porphyra (Bangiales,Rhodophyta) species in conjunction with environmental variables1

The effect of plant growth substances (PGSs) on conchocelis growth of Alaskan Porphyra (P. abbottiae V. Krishnam., P. pseudolanceolata V. Krishnam., P. pseudolinearis Ueda) was investigated. Growth was measured under different combinations of PGS concentrations (0, 0.1, 0.2, 0.4, 0.8, 1.6, and 3.2 ppm), PGS type (gibberellic acid, kinetin, and indole‐3‐acetic acid), temperature (7, 11, and 15°C), and photoperiod (16:8 light:dark [L:D] cycle and 8:16 L:D cycle). Plant growth substances effectively promoted the growth of Porphyra conchocelis. Depending on culture conditions, growth rates were increased relative to controls 6.9%–31.7% for P. abbottiae, 4.7%–25.7% for P. pseudolanceolata, and 8.9%–35.1% for P. pseudolinearis. Maximal growth of P. abbottiae occurred with 0.8 ppm kinetin, 15°C, and short‐day conditions (8:16 L:D). Porphyra pseudolanceolata exhibited maximal growth with 0.4 ppm indole‐3‐acetic acid, 7°C, and long days (16:8 L:D). Indole‐3‐acetic acid also effected maximal growth of P. pseudolinearis at 0.4 ppm, 15°C, and long‐day conditions (16:8 L:D). For P. abbottiae and P. pseudolinearis, intermediate PGS concentrations (0.4–1.6 ppm) had the greatest growth‐stimulating effects, whereas for P. pseudolanceolata, higher growth generally occurred at lower concentrations (0.1–0.8 ppm). Kinetin and indole‐3‐acetic acid had more influence on the conchocelis phase than gibberellic acid. The PGS concentrations greater than 1.6 ppm had a diminishing effect on growth, especially in P. pseudolanceolata. For P. abbottiae and P. pseudolinearis, higher temperatures resulted in higher growth rates, in contrast to P. pseudolanceolata, which grew faster at the lower temperatures.     

A morphological and molecular assessment of the genus Prionitis J. Agardh (Halymeniaceae, Rhodophyta)

A critical reassessment of the morphological features of two closely related red algal genera, Grateloupia C. Agardh and Prionitis J. Agardh (Halymeniaceae), shows that members of the two genera share very similar reproductive (including the Grateloupia‐type auxiliary‐cell ampullae) and vegetative characters. Diagnostic features hitherto used for distinguishing these two genera, the texture of blades (lubricous to leathery in Grateloupia vs cartilaginous in Prionitis) and the position of reproductive structures (scattered over the entire blade in Grateloupia vs confined to particular portions of the blade in Prionitis), are continuous across some 75 species of both genera, thus making it difficult to draw a clear‐cut distinction between the two genera. In ribulose‐1,5‐bisphosphate carboxylase/oxygenase gene (rbcL) sequence analyses, the species of Grateloupia and Prionitis, including the two generitypes, constitute a large monophyletic clade in the Halymeniaceae. It is therefore proposed that Prionitis be included in the synonymy under Grateloupia and the appropriate combinations are proposed.     

Population studies on a South African carrageenophyte: Iridaea capensis (Gigartinaceae,Rhodophyta)

An intertidal population of Iridaea capensis in the south-western Cape Province of South Africa has been studied in detail for a year. The species is generally restricted to sand-inundated rocky shores, which appears not to be the case for Iridaea species in the Pacific. In early winter (June) biomass, plant density and plant size were at a minimum. A small increase in these parameters occurred in August, but there was a massive increase in plant numbers and biomass in October. The largest plants were recorded in summer (February). The population was over 70% sporophytes in April, but switched to almost 80% gametophytes following heavy recruitment between August and October, and remained significantly gametophyte-dominated through April of the following year. Carrageenan levels were high (ca 42% of dry weight) in late winter-spring, and lowest (ca 30–35%) in summer-autumn. Strong offshore wind conditions in early summer caused a reduction in biomass, and it is hypothesized that the associated upwelling of nutrient rich water may be implicated in the lower carrageenan levels at this time.