Upright Thalli Research Articles

Effects of salinity and irradiance on early developmental stages of <italic>Grateloupia turuturu</italic> (Halymeniaceae, Rhodophyta) tetrasporophytes

<i>Grateloupia turuturu</i> is a red alga with a flat but firm slippery thallus. Throughout its lifetime, this alga experiences a wide range of environmental stresses in the intertidal rocky shores. The aim of this study is to investigate the effect of salinity and irradiance on the early developmental stages of <i>G. turuturu </i>tetrasporophytes. The released carpospores were cultivated at different salinities (S = 15, 25, and 35) and irradiances (50, 100, and 200 μmol photons m<sup>-2</sup> s<sup>-1</sup>). Germination of carpospores and development of juvenile tetrasporophytes were observed every 5 days and recorded by a digital camera. Discoid crusts were formed at all conditions within 5 days. The discoid crusts at 200 μmol photons m<sup>-2</sup> s<sup>-1</sup> died within 20 days regardless the salinity. The discoid crusts at S = 35 also died at all irradiance conditions within 25 days. Except for those at S = 35 and 200 μmol photons m<sup>-2</sup> s<sup>-1</sup>, the discoid crusts reached about 8,000–9,000 μm<sup>2</sup> by day 20. Regardless of irradiance, the upright thalli formation rate from discoid crusts was 85 and 10% at S = 15 and S = 25, respectively. These results suggest that salinity and irradiance are important factors influencing early developmental stages of <i>G. turuturu</i>.

A new red algal crust from New Zealand: Apophlaea darchinoae sp. nov. (Hildenbrandiales)

ABSTRACT New Zealand’s algal flora is still far from fully explored, and new taxa continue to be discovered. The taxonomy of the red algal order Hildenbrandiales, consisting mostly of crustose members, is controversial as descriptions are largely based on limited morphological features. The order Hildenbrandiales is also in a close, apparently obligate, relationship with an endophytic fungus. Apophlaea is a genus in this order currently comprising two described species, both endemic to New Zealand. The morphology of this genus is more complex than that of other members of the Hildenbrandiales as it consists of extensive upright thalli. Sampling of Apophlaea in New Zealand, especially in the southern part of the North Island, has led to the discovery of a genetically distinct entity, that is only crustose. We propose a new species for this entity, Apophlaea darchinoae sp. nov., which is found on rocks in the high intertidal zone. This species has the typical tetrasporangial conceptacles of Apophlaea and no other reproductive structures were observed, and it consists of filaments that are laterally joined by secondary pit connections. Apophlaea darchinoae can be found in sympatry with A. sinclairii in the north of the North Island. We provide molecular evidence for the distinct nature of A. darchinoae and provide observations of extensive fungal filaments within this new species.

Grateloupia oligoclora (Halymeniaceae, Rhodophyta): a new species from China based on morphological observation, life history and rbcL gene sequence analysis

ABSTRACT A new species of Grateloupia from Wenzhou Nanji Island in Zhejiang province, China, was illustrated based on morphological observation, early development, life history and rbcL gene sequence analysis, and named Grateloupia oligoclora H.W.Wang & Y.Bian sp. nov. The morphological features of this new species can be summarized as upright thalli, solitary or cespitose, dark red in colour, cartilaginous and mucilaginous in texture. The margins of the thalli were smooth, without lateral branches, proliferations, or branched, dichotomously branched or with 3–5 irregular rod-shaped branches. The thalli were consisted of cortex cells (6–9 cell layers) and medulla. The cystocarps were spherical and appeared to be speckled from the surface of the thalli. The carpogonial branch ampullae and auxiliary cell branch were typical Grateloupia-type. During the cruciate dividing of tetrasporangia, some dyads showed asynchronous phenomenon. Type of spore development and life history were typical mediate discal type and isomorphic alternation of generations. Phylogenetic analysis based on rbcL sequence indicated that the new taxon formed an independent clade from other Grateloupia species, and this clade was sister to G. subpectinata Holmes with high interspecific divergence 12 bp (1%), supporting its specific status. Accordingly, G. oligoclora H.W.Wang & Y.Bian sp. nov is proposed as a new species of Grateloupia. This study provides new resource and species diversity of marine Rhodophyta in China.

The morphological, developmental and molecular landscape of Grateloupia qingdaoensis Li et Ding

The rhodophyte marine algal genus Grateloupia (Halymeniaceae, Halymeniales) is distributed worldwide, including in offshore southeastern China. Here, we investigated morphology, carpospore development, ecological habits, and molecular analyses of a rarely studied species, Grateloupia qingdaoensis. The carpogonial branch ampullae and auxiliary cell ampullae were the typical Grateloupia type (6cpb-5auxb type) and the type of spore development was “mediate discal type”. The life history included homotypic gametophytes (haploid), carposporophytes (diploid), and tetrasporophytes (diploid) and showed a typical isomorphic alternation of generations. By using single-factor and orthogonal experiments, we explored the effects of temperature, irradiance and seawater salinity on the early development of G. qingdaoensis. Each ecological factor showed distinct effect on the early development of G. qingdaoensis. Additionally, we found a significant interactive effect between temperature and irradiance on discord crust growth. The optimum conditions for the early growth of discoid crust and upright thalli were 20 °C, 80 μmol photons m−2 s−1 irradiance and 30‰ seawater salinity. To clarify its taxonomical status, we constructed the phylogenetic tree of rbcL gene sequences. Results showed that there was no pairwise divergence between G. qingdaoensis and G. asiatica from China. Our findings indicate that previous records without precise and comprehensive comparison and molecular analyses need to be re-examined to clarify the global distribution of this species.

Seasonal population dynamics of Sargassum fusiforme (Fucales, Phaeophyta), Suo-Oshima Is., Seto Inland Sea, Japan\u2014development processes of a stand characterized by high density and productivity

Seasonal population dynamics of Sargassum fusiforme, one of the most important edible macroalgae in Japan, were studied. Recruits were mainly generated by vegetative reproduction at the margins of filamentous holdfasts. They first appeared in late spring and peaked in summer as upright thalli of the previous generation withered. After producing recruits, holdfasts withered indicating that holdfasts were also annual, the same as upright thalli. All recruits produced main branches and became new upright thalli in early autumn. During this transitional period, the thallus density decreased due to the crowded conditions induced by simultaneous growth initiation. After this early mortality, however, thallus density remained almost constant over much of the growth season. Thallus growth continued during winter and the stand biomass peaked in spring. During this biomass accumulation, development of a thallus size hierarchy was moderate and no size-dependent mortality was observed. Main branch number per thallus was also constant until spring, indicating the main branches also persisted after being produced in early autumn. This lack of severe intraspecific competition both at a thallus and main branch level is supported by the ambient wave condition of the habitat which gives moderate undulation and enables light and nutrients to be supplied to each thallus, and allowed the S. fusiforme stand to maintain its densely-packed feature with a high productivity.

Growth of gametophytes and sporophytes of Grateloupia subpectinata (Rhodophyta) in culture

Comparison of growing thalli in alternating haploid and diploid phases of Grateloupia subpectinata (Rhodophyta) was studied. Fertile thalli from gametophyte and tetrasporophyte of G. subpectinata were collected from Yangyang, on the eastern coast of Korea. The size of the released tetraspores and carpospores was measured; the spores were then incubated at the temperature of 20°C, irradiance of 40 μmol photon m-2s-1 and photoperiod of 12L and 12D. Carpospores were also cultivated in the same conditions as the tetraspores culture. The crusts were subsequently transferred to a tank culture after six months. The specific growth rate (SGR) was measured by observing 50 crusts and 30 thalli. The released carpospores had a larger diameter (9.98 μm) than the tetraspores (9.38 μm). The crusts from the carpospores also show a higher specific growth rate (14.04% d-1) than tetraspores (13.39% d-1). After being transferred and cultured in a tank, the upright thalli grew slowly in May-June (13–15°C) and rapidly in July–September (17–22°C). The length of growing thalli of sporophyte from carpospores also revealed a higher specific growth rate (2.83% d-1) than gametophytic thalli (2.38% d-1). The specific growth rate of crusts and thalli developed from carpospores was higher than that of the crusts developed from tetraspores. This result suggests that the cultivation of sporophytes may be more profitable than gametophytes because harvesting can be done more efficiently.

Developmental pattern of crust into upright thalli of Grateloupia asiatica (Halymeniaceae, Rhodophyta)

Grateloupia asiatica is an edible seaweed and source of carrageenan in Korea. Considering the economic importance of this edible seaweed, mass culturing methods from spores have been conducted. Moreover, it helps prevent natural population depletion. Spores germinate to form crusts, filaments and spherical structures that subsequently differentiate and develop into thalli. The objective of our research was to study the developmental pattern of crust into upright thalli. Vegetative cells of crust divided circularly to expand and coalescence with other crusts, while those cells that divide vertically increase the thickness of the crust. The specific growth rate of the crusts was optimal at 20 °C (8.6 % day−1) and 42 μmol photons m−2 s−1 (10.8 % day−1). At optimum condition, they grew in regularity that forming pattern of zonation and circular mounds onto the crusts subsequently produce upright thalli. Thalli would be generated if the crusts, generally composed of six cells in thickness, will start to produce cortical and medulla cells to support and generate upright thalli. In the tank culture, the upright thalli grew rapidly during July to October and reached a maximum length of around ±5.2 cm. The thalli matured and contained many carposporangia in the branches after 150 culture days.

Early development of grateloupia turuturu (Halymeniaceae, Rhodophyta)

Grateloupia turuturu is a commercial red alga with potential value in nutraceuticals and pharmaceuticals. To supplement information on its life history and verify whether carpospores can be used for seedling culture, early development of G. turuturu was investigated under culture conditions (27°C, 10–13 μol/(m2·s) in irradiance, photoperiod 10:14 h L:D). Three physiological stages were recognized by continuous microscopic observation: division stage, discoid crust stage, and juvenile seedling stage. At the beginning of the division stage, the carpospores developed germ tubes into which the carpospore protoplasm was evacuated, and then the carpospore protoplasm in the germ tubes began to divide continuously until discoid crusts formed. Finally, upright thalli appeared on the discoid crusts and developed into juvenile seedlings. It took about 60 days for carpospores to develop into juvenile seedlings. The growth parameters, including germination rate for carpospores and discoid crust diameter, were recorded. These results contribute more information on the life cycle, and at the same time are of great significance in the scaling-up of artificial seedling cultures of G. turuturu.

Nutrient content of macroalgae with differing morphologies may indicate sources of nutrients for tropical marine systems

To investigate whether tissue N and P content of morphologically distinct macroalgae reflect different processes controlling nutrient availability, we measured water column nutrients and collected 5 species of algae for tissue N and P analysis from 18 stations along the southwestern coast of Puerto Rico. Nutrient content of sediments was also determined for a subset of stations. South- western Puerto Rico was chosen because the literature suggests that gradients in sediment type and organic matter content, advection, and terrestrial influence occur in this region. Stations were either inshore or offshore areas with 3 stations per area chosen a priori as High Nutrient Stations (HNS). Water column and sediment nutrient concentrations were elevated inshore and in HNS. Species were of 3 morphological forms: upright thalli with open branches, densely packed mats, and rhizophytic thalli. In the first category, Acanthophora spicifera had higher N content inshore compared to off- shore while both A. spicifera and Hypnea musciformis had higher tissue N and P contents in HNS. In contrast, mat-forming algae (Dictyota dichotoma and D. cervicornis) had higher tissue N and P con- tents offshore compared to inshore. Although these species had high nutrients in many of the HNS, samples from some offshore reefs were equally high. Halimeda incrassata, a rhizophytic form, had greater tissue N content inshore than offshore. H. incrassata tissue nutrients were also elevated in some HNS, but not others. There were significant correlations between water column and sediment nutrients and the tissue N and P content of A. spicifera and H. incrassata, but not for either Dictyota. These results suggest algae with upright thalli and open-branching patterns may have a more direct relationship between tissue nutrient content and water column nutrient concentration than other forms. In contrast, mat-forming species may deplete nutrients within the mat, relying on strong cur- rents found offshore to penetrate dense mats and replenish nutrients. Rhizophytic algae have access to both water column and sediment nutrients, and higher inshore tissue contents and at some HNS may reflect enhanced nutrient supplies from these sources. Our findings suggest that if other envi- ronmental factors are carefully taken into consideration, the tissue N and P content of macroalgae may prove to be an effective indicator of different nutrient sources in tropical systems.

Leeward bank margin Halimeda meadows and draperies and their sedimentary importance on the western Great Bahama Bank slope

Bryopsidalean algal meadows in water depths of 20–40 m on the leeward side of western Great Bahama Bank (WGBB) lie between non-skeletal-dominated sand flats on the bank top to the east and a cemented steep escarpment to the west. The meadows contain dense populations of rhipsalian Halimeda species, as well as Udotea and Rhipocephalus. Extensive populations of other Halimeda species (opuntioids) occur at greater depths on the cemented rocky escarpment, growing as drapes or vines rather than as upright thalli. These meadows and draperies are important sources of coarse-grained carbonate sediments. This is shown by (1) deeper bank-edge sediments (30–60 m) containing considerably more Halimeda fragments than do the bank top, non-skeletal sands, and (2) the coarser fraction of slope sediments (down to 200 m) dominated by Halimeda plates, partly or extensively altered and internally cemented by magnesian calcite and aragonite. A transect across the bank margin from bank top (<10 m) to lower slope (300 m) provides a useful comparison for the locus of sediment production and accumulation. The production of Halimeda in these bank-edge habitats approximates that in the Great Barrier Reef or off Indonesia and Nicaragua in similar water depths. The apparent lack of thick sediment accumulation in WGBB compared to that seen elsewhere may reflect the high rates of downslope transport off Great Bahama Bank.

Seasonal growth and photoinhibition in Plocamium cartilagineum (Rhodophyta) off the Isle of Man

Abstract Length frequency determinations in subtidal populations of Plocamium cartilagineum provided information on growth of upright thalli in relation to season and depth. At 2 m below lowest astronomical tide (LAT), under the laminarian canopy, growth started in March and was exponential until June, with a relative growth rate in weight of 0.026 per day. Under wave exposed conditions few mature uprights survived into the following winter. In deeper water, under the laminarian canopy, growth was slower and deeper still (13–17 m) mature uprights survived throughout the year. Clearance of the phaeophycean canopy allowed faster growth over an 8 m depth range but in early summer appeared to reduce the growth at 1 m below LAT. Uprights held on blocks at 0.5 m below LAT and in tanks exposed to reduced mid-summer daylight grew more slowly than uprights receiving less irradiance. It seemed that 0.5 mmol m−2 S−1 was inhibitory. These data agree with the concept of the species as ‘shade loving’, with a maximum re...

Observations on the life histories of Punctaria plantaginea (Roth) Greville and Punctaria orbiculata Jao (Punctariaceae, Phaeophyta)

Abstract The life histories of P. plantaginea (Roth) Greville and P. orbiculata Jao are described from laboratory culture. Both showed an apparently asexual, ‘direct’ life history. In P. plantaginea from Newfoundland, Canada, plants bear only unilocular sporangia. Unispores gave rise to two successive culture generations of unilocular sporangium-bearing plants. In P. orbiculata from the type locality for the species on San Juan Island, Washington, plurispores produced successive culture generations of plants which formed first plurilocular and then unilocular sporangia. A similar sequence was apparent in the field. No sexual reproduction was observed, although the fate of unispores was not followed. There is some evidence to suggest that the rate of formation of upright thalli and sporangia are environmentally influenced.