Seasonal agar yield and quality inGelidium canariensis (Grunow) Seoane-Camba (Gelidiales,Rhodophyta) from Gran Canaria,Spain

The seasonal effects on yield and gel properties ofGelidium canariensis agar were investigated at two intertidal populations at the northern coast of Gran Canaria. Physical and rheological properties were measured in 1.5% w/v solutions after treatment with alkali. No significant differences were found on agar characteristics between the two sites studied. The highest yields were obtained during summer with a maximum in June (27.8%) and minimum during late autumn and winter (18–18.6%). Overall quality was highest in winter (November–January), when gel strength peaked above 850 g cm^–2. The results showed an agar of industrial quality.     

Protoplasts of Gelidium robustum (Rhodophyta)

Viable protoplasts were isolated from apices of the agarophyte Gelidium robustum (Gardn.) Hollenb. & Abb. using a combination of commercial cell-wall degrading enzymes and extracellular wall-degrading enzymes isolated from a marine bacterium. The protoplasts were approximately 8–15 µm in diameter, liberated mainly from the surface cell layers and from cells at the distal ends of medullary filaments. The bacterial enzyme alone was not sufficient to liberate significant numbers of protoplasts. Maximum yield was 9 × 10⁵ protoplasts/g tissue (wet wt.). Optimum osmolality occurred between 1750–1950 mOs kg^–1; yield and viability were severely diminished at osmolalities less than 1350 mOs kg^–1. Viability, as determined by flurorescein diacetate staining and Evans Blue exclusion 1 hr after removal from the enzyme solution, was approximately 80–95%. Roughly 80% of the cells did not show Calcofluor fluorescence, while 40% stained positively for the presence of sulfated polysaccharides. Cell wall regeneration was observed with inconsistent reproducibility, and no cell division was observed when the protoplasts were placed in culture medium.Dedicated to the memory of Professor Michael Neushul.     

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.     

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.     

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.     

Spray system for re-attachment of Gelidium sesquipedale (Clem.) Born. et Thur. (Gelidiales: Rhodophyta)

A system is described for rapid re-attachment of the rhodophycean alga Gelidium sesquipedale (Clem.) Born. et Thur. on artificial or natural substrata. This method is applicable to industrial cultivation of this species. The function of rhizoidal clusters and the origin of germlings from the apical portion of the thalli are analyzed in relation to the re-attachment process. The role that re-attachment might play in the maintenance and spreading of natural populations and in the observed anomalies of the life-history of this species is discussed.     

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.     

Spatial and temporal variation in distribution of Gelidium canariensis (Rhodophyta) from natural populations of the Canary Islands

This study was designed to investigate spatial and temporal variation in Gelidium canariensis populations at two shores in northern Gran Canaria during two years. Spatial scales ranged from some hundred meters (distance between shores), 10 to 30 m (distance between plots) to less than 3 m (distance between quadrats). Gelidium individuals were defined as distinct Gelidium clumps. The results show a significant difference in size of clumps between shores, but not on the smaller spatial scales. No significant temporal variation was found. There was no significant temporal or spatial variation in standing crop or density (counts made in quadrats where Gelidium was present, rather than counts for the total shore). Sporophytic and gametophytic clumps were also distinguished by identifying reproductive structures in the field. The total proportion of sporophytes was larger than the proportion of gametophytes, but at a smaller scale there could be a shift in dominance. The survival rate of clumps was similar between shores with a mean survival rate of 85%, but there was a significant difference in recruitment between shores. The results indicate a stable population structure. This revised version was published online in June 2006 with corrections to the Cover Date.     

Physiological basis for the cultivation of the Gelidiaceae

An understanding of the physiological factors important to growth and agar production of the Gelidiales would be useful for successful mariculture of these commercially valuable plants. Several environmental factors, including light, nitrogen, carbon, temperature and water motion, have been shown to have potential significance for growth rates, reproduction and carbon partitioning in defining optimal conditions for cultivation. Limiting and optimal growth conditions, where known, are presented, and evaluation of data reported in the literature is addressed.     

A study of the phycocolloids from Gelidium madagascariense and Eucheuma denticulatum (Rhodophyta) collected on the south coasts of Madagascar

Several species of red algae known to contain agar or carrageenan are abundant on the southeast and southwest coasts of Madagascar. The agarophyte Gelidium madagascariense, collected in the Fort Dauphin area, has been exported on a small scale to Japan for several years. FT-IR and GLC analysis show that it contains an agar polymer, of which the methylated fraction contains predominantly 6-O-methyl galactose and traces of 4-O-methyl galactose. Eucheuma denticulatum grows profusely on the coral reefs in the Tulear area. FT-IR and GLC analysis show that it contains iota-carrageenan, with no methyl-derivative contaminants. The 3,6-anhydro-galactose content was found to be rather low, suggesting a possible contamination with deviant iota. The economic potential of other sources of phycocolloids, as well as the possibility of farming different species of Eucheuma in the Tulear area, is discussed.     

Artificial sporeling and field cultivation of Gelidium in China

The supply of Gelidium resources is dependent on collection from natural habitats. As these resources are very limited, one possible means of augmenting production is by implementation of artificial cultivation as has been done with Laminaria, Porphyra and Eucheuma. Chinese phycologists have conducted research on sporeling and field cultivation of Gelidium for many years. Trials have been made using: (1) raft cultivation based on vegetative propogation of thallus fragments, (2) cultivation based on spore-collecting and land-based tank culture to provide seedstock, (3) cultivation based on regeneration from small thallus fragments to provide seedstock. Some of these results have been promising, but development remains at the experimental stage and methods of cultivation need to be improved. This paper is an updated review of the research and development on artificial sporeling production and field cultivation of Gelidium in China.     

Field studies and growth experiments on Gelidium latifolium from Asturias (northern Spain)

Seasonal cycles of environmental factors (temperature, day-length, nutrient concentration) and changes in Gelidium latifolium biomass, percentage reproduction and size are given, and non-parametric correlation is used to quantify possible relationships. The results are compared with growth experiments, testing effects of total light dosage, agitation, temperature and Photon Flux Density (PFD). Results of total light dosage × agitation growth experiment show that maximum growth is obtained when plants are cultured at a long photoperiod (16 : 8 L/D) with agitation. Results of temperature × PFD experiment show that maximum growth is obtained at PFD values higher than 50 µE m^–2 s^–1 at temperatures between 20–25 °C. Possible applications of field studies and culture experiments in management of wild resources and industrial cultivation are proposed.     

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.     

Effect of a cationic cellulosic polymer on gametophytes of Laminaria digitata (Laminariaceae, Phaeophyta): Improvement of dispersed `free-living' cultures

As filament aggregation is responsible for heterogeneity of Laminariales gametophyte cultures, a project was conducted to obtain stable homogeneous `free-living' cultures of Laminaria digitatagametophytes. The alga was cultivated at 15 ^° Cunder low light and in the presence of a cationic cellulosic polymer, JR125. With 0.1%polymer in the culture medium, the filaments were dispersed and did not adhere to the culture vessel. The absence of any effect of the closely related, but uncharged, polymer LR-250 Natrasol on filament aggregation indicated that the cationic nature of the JR125 molecule was involved in gametophyte dissociation. In the presence of JR125, the gametophytes showed active vegetative growth; the doubling time, measured as chlorophyll concentration, was 5 days. The outer surface of the cell wall was clearly modified by the polymer treatment, as observed by transmission electron microscopy, while neither the inner cell wall or cell organelles were affected. Physiological studies indicated that JR125 treatment did not disturb cell physiology, there being no effecton respiration, photosynthetic activity, sensitivity to high-light stress or modification of pigment or fluorescence characteristics. We have therefore established the conditions for maintaining a stable culture of mixed male and female Laminaria digitata gametophytes in active vegetative growth. The presence of JR 125 in the medium yields a homogeneous culture without cell physiology becoming modified. This revised version was published online in August 2006 with corrections to the Cover Date.     

Factors affecting protoplast yield of the carrageenophyte Solieria filiformis (Gigartinales,Rhodophyta)

Summary The effect of age, pH of the culture medium, pre-treatment of tissues, enzymes sources and enzymatic adaptability of phycophages fed with a monospecific diet were analyzed on the protoplast yields of the red seaweed Solieria filiformis (Kützing) Gabrielson. New apices from fast growing plants showed the highest protoplast yields. The protoplast yield decreased when the pH of the culture medium increased from 6.0 to 9.0. Crude extracts from the abalone Haliotis coccinea canariensis Nordsieck, fed with Solieria filiformis thalli for three months in combination with cellulysin, released the highest number of viable cells and protoplasts. Yields ranged from 1.0 to 8.5 x 10⁶ protoplasts per gram of fresh weight.Abbreviations AAP abalone acetone powder - Bis-Tris Bis(2hydroxyethyl)imino-tris(hydroxymethyl)methane - CMC carboxymethyl cellulose - EDTA ethylenediaminetetraacetic acid - EGTA ethylene glycol-bis(ß-aminoethyl ether) NNNN-tetraacetic acid - FDA fluorescein diacetate - FW fresh weight - Hepes N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - Tris Tris(hydroxymethyl)aminomethane     

Architectural models for apical patterns in Gelidium (Gelidiales, Rhodophyta): hypothesis of growth

The great morphological variation in the apical region of main axes and branches in species of Gelidium and Pterocladia suggests different patterns of growth. Those patterns have been reconstructed from the ontogenetic sequence of morphological stages and regeneration of the apex. Using the architectural approach, models for four species of Gelidium from the Pacific coast of central Chile and the Pacific coast of Mexico's tropical region, were constructed based on the following criteria: growth pattern, specialization of laterals, symmetry, apical dominance and rhythm of apical and lateral growth. Those models allow for a formal evaluation of apical differences between species.     

Growth and reproductive characteristics in artificially formed clonal gametophytes ofDryopteris filix-mas (Dryopteridaceae)

Artificially formed clonal gametophytes ofDryopteris filix-mas (L.)Schott were able to grow and reproduce, although growth rates, proportions of hermaphrodites and reproductive efforts were low. Variable density and nutrient levels appeared to affect gametophytic life histories and they continued to influence the viability of the developing sporophyte generation. Differences between populations and sporophytes were discovered in life histories. Hermaphroditic gametophytes were considerably larger and possessed higher viability than did males. Clear differences between clones in the level of phenotypic plasticity in gametophyte size were observed. No neighbor effect on gametophyte sex expression was detected with the densities and nutrient levels used.