Temporal and spatial variation in agar from a population of Pterocladia capillacea (Gelidiales,Rhodophyta) from Brazil

Pterocladia capillacea forms dense intertidal belts in southeastern Brazil, on moderately exposed rocky coasts. The studied population extends along a gradient of water exposure, where slightly different morphotypes can be recognized. Specimens were collected monthly from 3 points along the exposure gradient of its distribution (lower, medium and higher exposure), and analyzed for agar, sulfate and 3,6 anhydrogalactose content. Agar varied from 5–32% of dried seaweed with lower yields in the winter, and higher yields in late spring/early summer. Specimens from the surf side of the distribution had a consistently higher agar content throughout the year. Sulfate varied from 1–5%, and 3,6 AG from 27–48% of dried agar, without a clear variation among the sites.     

Resource biology of Pterocladia capillacea (Gelidiales,Rhodophyta) populations in Brazil

Pterocladia capillacea has been already exploited in Brazil and Uruguay, but exploitation was discontinued due to source depletion. Our attempts to cultivate this species in the sea, or in tanks, gave poor results. In this communication we present some ecological data as a contribution to evaluate the possibility of a production increase in natural beds on the southeast coast of Brazil.Our results show that: (i) the populations are perennial varying from 323 (i.c._0.05 = 51) to 600 (i.c._0.05 = 78) g dry weight throughout the year; (ii) horizontal distribution is affected by irradiance, with higher biomass in shaded areas and by water movement, with higher biomass in intermediate sites; (iii) vertical distribution is limited above by desiccation and below by herbivores — sea urchins removal increases cover by 20–50%; (iv) Sargassum vulgare is the main competitor for space, and its removal on areas of contact between both populations increases coverage of P. capillacea by ca 80%.     

Physiological responses of Pterocladia and Gelidium (Gelidiales,Rhodophyta) from the Azores,Portugal

Manometric studies were conducted on Pterocladia capillacea, Gelidium latifolium and Gelidium spinulosum from the Azores, Portugal to determine optimal values of temperature, light and salinity for growth. Physiological responses were considered in relation to vertical distribution patterns of these species commonly observed throughout the Azores. Optimal parameters for the growth of Pterocladia capillacea, Gelidium latifolium and G. spinulosum were 17 to 25 °C, a photon flux density between 200 and 300 µmol m^–2 s^–1 and salinities of 25 to 35.     

Field and culture studies of species of Gelidium (Gelidiales,Rhodophyta) from their northern limit of distribution in Europe

Two species of Gelidium, provisionally referred to as G. pusillum and G. latifolium, are included in the Scandinavian flora and reach their northern limit of distribution on the Norwegian west coast. Small frond sizes due to adverse growth conditions, extreme phenotypic variability and lack of sexual reproduction make identification of specimens very difficult. Both species were isolated into unialgal culture and were compared with cultured strains referable to G. pusillum from Ireland and France. Temperature and salinity requirements and tolerance ranges were determined and discussed in view of distribution along the Norwegian coast. Little or no growth occurs below 9 °C, corresponding to a northern summer growth limit. On the Norwegian Skagerrak coast, low winter temperature rather than reduced salinity is the limiting factor.     

Spore Adhesion and Cell Wall Formation in Gelidium Floridanum (Rhodophyta, Gelidiales)

The attachment of spores to a substratum is essential for their germination and, therefore, to the completion of the life cycle of the red algae. In most red algae, spores are liberated without a cell wall, within a sheath of mucilage which is responsible for their primary attachment. Utilizing fluorescent-labeled lectins, we identified carbohydrate residues and their locations in the mucilage and cell walls of spores of Gelidium floridanum. Cell wall formation and mucilage composition were studied with calcofluor, toluidine blue (AT-O), alcian blue (AB) and periodic acid-Schiff (PAS). In the mucilage we identified α-D mannose, α-D glucose, β-D-galactose, N-acetyl-glucosamine and N-acetyl-galactosamine. The first two sugar residues were not found in the cell wall of the germ tube but they were present on the rhizoid’s cell wall indicating their importance to substrate adhesion. A cell wall is produced soon after the spore’s attachment, beginning with a polar deposition of cellulose and its gradual spread around the spore as indicated by calcofluor. The cell wall matrix was positive to AB and metachromatic to AT-O, indicating acidic polysaccharides, while cellulose microfibrills were positive to PAS. A polar disorganization of the cell wall triggers the process of germination. As spores are the natural form of propagation of Gelidium, the understanding of the mechanisms of spore attachment may contribute to the cultivation of this valuable seaweed.     

Advances in cultivation of Gelidiales

Currently, Gelidium and Pterocladia (Gelidiales) are collected or harvested only from the sea. Despite several attempts to develop a cultivation technology for Gelidium, no successful methodology has yet been developed. Initial steps towards developmental efforts in Portugal, Spain, South Africa and Israel have been published. More developments have probably been performed but have not been published. Two different technological concepts have been tested for Gelidium cultivation: (1) the attachment of Gelidium fragments to concrete cylinders floating in the sea, and (2) free-floating pond cultivation technology. These vegetative cultivation technologies might be partially optimized by controlling physical, chemical and biological growth factors. The pond cultivation technology is the much more controllable option. The effects of all factors are discussed in detail in this review. It seems that the main difficulty with cultivation of Gelidium is its low growth rate. The claimed yields of the two technologies are far from being economically attractive at this stage of their development. It seems that in order to introduce Gelidium into commercial cultivation, major efforts in genetic improvement through selection or genetic engineering will be required. Only high yield strains will have the potential to compete economically with the present harvesting tradition. However, accumulated experience with genetic improvement of other useful seaweed species suggests that this is possible.     

Agars from Gelidium rex (Gelidiales,Rhodophyta)

Gelidium rex grows in the rocky intertidal of central Chile. Extraction of vegetative G. rex with water at 95 °C yielded 17.9% of agar with a gel strength value of 590 g cm^–2. The gel strength increased up to 1272 g cm^–2 when the alga was treated with alkali prior to extraction. Cystocarpic and tetrasporic thalli of G. rex were extracted with distilled water at 95 °C, affording soluble polysaccharides in 36.0% and 15.7% yield respectively. Polysaccharides of both life history phases were fractionated by chromatography on DEAE Sephadex. Elution with distilled water gave fractions devoid of sulfate; the fraction from cystocarpic plants contained 45.5% of 3,6-anhydrogalactose whereas the neutral fraction from tetrasporic plants contained 40.0% of 3,6-anhydrogalactose. Further elution with 0.1, 0.4, 0.8 and 1.5 molar aqueous solutions of KCl afforded four fractions for each polysaccharide. Chemical analysis of these fractions showed that the agars from cystocarpic and tetrasporic Gelidium rex are mixtures of related polysaccharides that range from neutral polymers to highly sulfated galactans.     

Vegetative propagation by fragmentation of Gelidium sclerophyllum (Gelidiales,Rhodophyta)

Results of the first phase of production of "seed" for a project of marine culture of species of Gelidiales are presented. Vegetative fragments of different sizes and from different parts of the thallus of Gelidium sclerophyllum from the Mexican tropical Pacific coast were cultured under nine treatments with different N and P concentrations. In treatments without N all fragments died; good vegetative growth was present in all remaining treatments. Growth in length and branch production were favored in medial fragments, and rhizoid production was favored in apices. Growth in length and biomass increase were stimulated by high N concentrations (2–3 mM), and branch and rhizoid production were stimulated by high P concentrations (100–150 µM).     

Fecundity,spore recruitment and size in Gelidium sesquipedale (Gelidiales,Rhodophyta)

Gelidium sesquipedale fecundity was quantified by counting tetrasporangial sori and cystocarps per meter squared and by estimating the number of spores contained inside them. These were obtained by regression on a size metric of reproductive structures. Tetrasporangial sori length and cystocarp thickness were the best estimators of spore number. To assess spore recruitment, 12 pottery tiles were fixed to the bottom, and the appearance of small fronds was monitored.No clear seasonal pattern of reproduction was found. Tetraspore production peaked in March 1990 with 10.4 × 10⁶ spores m^–2, whereas the carpospore peak was lower, 4.9 × 10⁵ spores m^–2 in July 1989. Recruitment followed tetraspore peaks. The probability of a G. sesquipedale tetraspore making the transition to a recruit was 4.7 × 10^–5. Frond length was significantly related to tetrasporangial sori number, while cystocarp number was only related to frond branching order. Minimum size for reproduction was 6.9 cm for gametophytes and 5.4 cm for tetrasporophytes; very rarely were cystocarpic fronds smaller than 9 cm, while tetrasporic fronds were often longer than 15 cm. Cystocarpic fronds were significantly shorter and had more branches than tetrasporic fronds.     

The effect of phosphate concentration on growth and agar content of Gelidium robustum (Gelidiaceae,Rhodophyta) in culture

Phosphate concentration of the growth medium was found to affect the growth rate and agar yield of a clone of Gelidium robustum grown in the laboratory. To study differences in growth we used phosphate concentrations from 0 to 200 µM. To determine the effect of phosphate on agar yield and its properties we used concentrations from 0 to 20 µM. Growth rates generally increased with increasing phosphate concentration, with the highest growth rate (21% d^–1) obtained at 150 µM. Agar yield as percentage of fresh weight was highest (10%) in the algae grown with low phosphate concentrations, but agar yield as percentage of dry weight was highest(43%) at 20 µM of phosphate. Gel strength increased with phosphate concentration with a maximum of 160 g m^–2 for 0.75% gels for the cultures at 20 µM. Melting and gelling temperatures of the gels were also affected by phosphate concentration of the growth medium. Starch yield was highest in algae grown in low phosphate concentrations.     

Taxonomic review of the species of Pterocladia (Gelidiales, Rhodophyta)

Segregating Pterocladiella from Pterocladia stimulated new taxonomic studies of the species originally assigned to Pterocladia. A total of 28 species are ascribed to the genus, one of them with doubts. Thirteen of the 27 names are synonyms. Three of the remaining 14 species belong with Gelidium, including G. americanum, G. mcnabbianum (Dawson) comb. nov. and G. musciformis. Seven other species belong with Pterocladiella, including P. bartlettii (Taylor) comb. nov., P. bulbosa, P. caerulescens, P. caespitosa (Kylin) comb. nov., P. caloglossoides (Howe) comb. nov., P. capillacea and P. melanoidea. Two species are retained in Pterocladia, the type P. lucida and P. rectangularis. Two others, P. heteroplatos and P. media are placed in incertae sedis as additional studies of fertile materials are needed to determine their generic status. The genus Pterocladia now appears to include two large-sized species restricted to Australia-New Zealand. Pterocladiella has 8 small-sized species (including P. minima), mainly inhabiting tropical and subtropical waters. Future research documenting sexual reproduction in Gelidiella and solving the presently recognized heterogeneity in Gelidium will help to trace the relationships between Pterocladiella and these two genera. This revised version was published online in June 2006 with corrections to the Cover Date.     

Studies on Chinese species of Gelidiella and Pterocladiella (Gelidiales,Rhodophyta)

A previously unknown species of anostracan is presented and described herein as Eubranchipus stegosusn. sp. This species is unique in that the male bears large, sub-quadrate, transverse, dorsal thoracic projections. Eubranchipus stegosus n. sp. is most closely related to E. moorei and E. holmani and may be endemic to southwestern Georgia. However, anostracans are poorly sampled throughout the southeastern United States, and additional surveys should be conducted to better understand this species' distribution and degree of rarity.     

First report of Gelidiella ligulata (Gelidiales, Rhodophyta) in Japan

A gelidialean red alga that was newly found in Japanese waters is referred to as Gelidiella ligulata Dawson. It is characterized by erect lanceolate blades developing from a creeping axis that are relatively large in the genus Gelidiella. Among the 22 species currently recognized in the genus, Gelidiella indica Sreenivasa Rao is most similar to G. ligulata and a further comparative study is needed to elucidate the status of G. indica. Gelidiella ligulata and the type species of the genus, Gelidiella acerosa (Forsskal) Feldmann et Hamel, have the unicellular independent attachments that are common to the members of Gelidiella investigated to date. This type of attachment is unique in the Gehdiales and this feature may be a useful taxonomic criterion in distinguishing Gelidiella from other genera.     

Reassessment of the taxonomic status of Gelidium subfastigiatum (Gelidiales, Rhodophyta)

The taxonomic relationship between Gelidium elegans Kützing and Gelidium subfastigiatum Okamura, two morphologically similar species of the red algal genus Gelidium (Gelidiaceae) growing in the north‐western Pacific, was critically re‐examined. Gelidium subfastigiatum has been distinguished from G. elegans by its more robust thalli, which have antrorse tooth‐like branches, although their distinction has been said to be often difficult or impossible. We determined the nuclear encoded internal transcribed spacer 1 (ITS1) for 14 samples from eight populations of this G. elegans/ G. subfastigiatum complex, and two types of ITS1 sequences were found. Analysis of seasonal variations of subterminal portions of major branches revealed that this complex includes two groups: one possessing the type 1 ITS1 sequence and antrorse tooth‐like branches that are subterminally thickened and widened during only colder months, and another possessing the type 2 ITS1 sequence and thin and narrow branches throughout the year. These groups should be recognized as separate species; the former is assigned to G. subfastigiatum and the latter to G. elegans.     

Annual variations of the biochemical composition of Gelidium latifolium (Greville) Thuret et Bornet

Agar, floridean starch, protein, ash and water content in Gelidium latifolium from nature were followed monthly over one year. Comparison of variations in these contents, algal growth and cytological observations enable us to establish a cycle for agar synthesis. In autumn, after reproduction of alga, there is an active algal growth period with agar synthesis and utilization of floridean starch. In winter, synthesis is shifted toward protein accumulation while there is a partial agar hydrolysis. In spring another active growth period of the alga occurs with accumulation of floridean starch and synthesis of agar. In summer and during reproduction, there is a depletion of thalli nitrogen content while the agar synthesis pauses.     

Phylogenetic Diversity of New Zealand Gelidiales as Revealed by rbcL Sequence Data

Diversity and phylogenetic relationships of New Zealand representatives of the red algal order Gelidiales have been examined using rbcL sequence data. Extensive field collections have been made from throughout the New Zealand region. Six genera have been reported previously from New Zealand (Capreolia, Gelidium, Pterocladia, Pterocladiella, Pterocladiastrum, Ptilophora). This research has revealed species with very restricted local distributions, as well as the discovery of several undescribed, cryptic taxa. The common and widespread Gelidium caulacantheum is confirmed to be more closely related to Capreolia than to other species of Gelidium. The generic concept of Capreolia, based on life history characters, will need to be modified to accommodate additional species possessing “Gelidium” life histories. A species endemic to New Zealand, Gelidium ceramoides, has been found to differ significantly from all other members of the Gelidiales and requires reclassification in another genus and order. Examination of field collections and herbarium specimens in addition to molecular sequence data have led us to conclude that specimens previously placed in the genera Ptilophora and Pterocladiastrum belong within Pterocladia lucida.