Gelidium (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Gelidium amansii - 1, portion of an upper branch of a tetrasporic thallus; 2, part of a terminal branch with tetrasporangia; 3, portion of an upper part of a branch of a cystocarpic thallus. G. pusillum var. pacificum - 4, habit; var. pusillum - 5, cross-section of an erect, terete part of a thallus; 6, cross-section of a flattened part of a thallus; 7, apex with apical cell in surface view; 8, cortical cells in surface view. G. crinale - 9, habit.

Gelidium J.V. Lamour.

Protologue: Ann. Mus. Hist. nat. (Paris) 20: 128 (1813) (= Essai Thalassioph.).

Family: Gelidiaceae

Chromosome number: x= 4-5, 2n= 9-10 or 20

Major species and synonyms

• Gelidium amansii (J.V. Lamour.) J.V. Lamour., Ann. Mus. Hist. nat. (Paris) 20: 129 (1813), synonyms: Fucus amansii J.V. Lamour. (1805), Gelidium elegans Kütz. (1868).

• Gelidium australe J. Agardh, Lunds Univ. Årsskrift 8(III, Mat. Nat. 6): 30 (1872).

• Gelidium capense (S.G. Gmelin) P.C. Silva, in P.C. Silva, E.G. Meñez & R.L. Moe, Smithsonian Contr. Mar. Sci. 27: 26 (1987), synonyms (c.q. misapplied names): G. versicolor (S.G. Gmelin) J.V. Lamour. (1813), G. cartilagineum (L.) Gaillon (1828).

• Gelidium crinale (Turner) Gaillon, Dict. Sci. nat. (Cuvier) 53: 362 (1828), synonym: Fucus crinalis Turner (1811-1819).

• Gelidium latifolium Bornet ex Hauck - see separate article (as G. spinosum).

• Gelidium pulchellum (Turner) Kütz., Tab. phycol. 18: 18, Tab. 53, figs e,f (1868), synonym: Fucus corneus Hudson var. pulchellus Turner (1819).

• Gelidium pusillum (Stackh.) Le Jol., Liste alg. mar. Cherbourg: 139 (1863), synonyms: Fucus pusillus Stackh. (1795), Acrocarpus pusillus (Stackh.) Kütz. (1849).

• Gelidium spinosum (S.G. Gmelin) P.C. Silva - see separate article.

Vernacular names

• Indonesia: agar-agar (general), cin-cao (a Chinese term for agar jelly used in Ambon).

Origin and geographic distribution

Several Gelidium are distributed worldwide, and are even found in cold temperate areas as far apart as the Falklands and south-western Norway. G. amansii is recorded in the Indian Ocean (Madagascar, Mauritius, India, Thailand, Peninsular Malaysia and Singapore) and Asian parts of the Pacific (Japan, the Philippines, Indonesia). There is, however, much discussion about the correct naming and identification of this species; especially its occurrence in the Philippines and Indonesia is challenged. Although this alga is often cited as found in South-East Asia, localities are not specified. G. crinale is found in all tropical and subtropical waters including those around Thailand, Malaysia, Vietnam (Nha Trang), the Philippines (Negros: Ilacan, Apo, Cebu) and Indonesia (Kai Besar, Lombok, Timor). G. australe and G. pulchellum are rather limited in distribution. The former species is well known in Australia and New Zealand. The latter has so far, in Asia, only been recorded in Burma (Myanmar), Peninsular Malaysia and Singapore, Vietnam (Nha Trang) and the Philippines (Luzon: Pangasinan, Batangas). G. pusillum is a name widely used for small Gelidium spp. occurring in temperate, subtropical and tropical waters. In South-East Asia it has been recorded in both the Indian Ocean in Burma (Myanmar), Thailand and Indonesia as well as in the South China Sea in Thailand, Malaysia, Vietnam and the Philippines. G. capense is possibly endemic to South Africa, although it has been often recorded (as G. cartilagineum) from many localities in the world, including the Philippines.

Uses

In several subtropical countries especially G. amansii and G. capense (as G. cartilagineum) are extracted to produce high quality agar, a sulphated polysaccharide used widely in the food, pharmaceutical and cosmetic industries. Traditionally Gelidium is consumed as a vegetable and for making agar jelly. Gelidium is frequently eaten raw, but can also be steamed or cooked and mixed with spices before being served.

Production and international trade

Gelidium is harvested in large quantities in subtropical waters such as in Japan, Korea, Spain, Portugal and Morocco. In the world market, the major source of agar comes from gelidioid algae (viz. the Gelidiales Gelidiella Feldmann & Hamel, Gelidium and Pterocladia J. Agardh) and from gracilarioid algae (Gracilariales: Gracilaria Grev. and Gracilariopsis E.Y. Dawson). Quantitative data which reflect the contribution of Gelidium to the agarophyte market reveal that in 1989 47% of the production of agarophytes was from Gelidiales and 53% from Gracilariales. It was stated that Gelidium alone accounted for 44% of all agarophyte production. In 1990 120 000 t (wet weight) of Gelidium were available for agar production, resulting in an estimated world production of 21 500 t (dry weight) of these dried seaweeds. Japan is currently the largest agar producer and exporter in Asia, the average agar export from this country being 713 880 t/year (1984-1986). In 1977 dry Gelidium had a value of US$ 1000-1200 per t. Amongst South-East Asian countries, only Indonesia and the Philippines export some Gelidium. However, that quantity is relatively small, i.e. 62 t from Indonesia and 3 t from the Philippines in 1984, and most probably includes Gelidiella acerosa (Forssk.) Feldmann & Hamel as is the case for the other data on Gelidium production in Indonesia. For 1989 the amount of Gelidium in Indonesia used for agar production was estimated at 1400 t (dry weight), while the total amount of Gelidium in Indonesia that year was estimated at 21 500 t (dry weight). In 1991 Indonesia probably exported a total 59 t of dried "Gelidium" to New Zealand and Italy.

Collection in Indonesia is spread over a wide area; the southern coast of Java yields about 30% of the total, the islands between Java and Timor about 25%, Sumatra about 15%, and the remainder comes from several areas to the North and East of Timor. The total area which could be used to produce Gelidium in Indonesia is 4700 ha, which would be capable of producing 4500 t (dry weight) from natural populations.

Properties

The agar from gelidioid algae is better than that from other tropical agarophytes and the agarose component is dominant. The agar content in the gelidioids is usually low (19-29%). Extraction from G. amansii from Taiwan produces 22-36% agar and G. capense produces 15-20% agar. Gelidium contain water, fat, protein, fibre and minerals. For G. amansii from Japan 100 g dried algae contain: water 14-20 g, fat about 0.4 g, protein 16.1-22.5 g, fibre 10.5-13.5 g and minerals 3.5-8.5 g.

Description

• Plants of moderate to small size, 1-30 cm tall, with erect axis and usually laterally branched; branches firm, cylindrical or flattened, consisting of a central row of cells surrounded by pericentral cell and later paralleled by many other secondary medullary filaments; cortex cells assimilatory, short, compact, arranged in radial rows; rhizines generally present in the inner layers of the cortex or somewhat dispersed.
• Life cycle triphasic, haplo-diplontic, isomorphic and with dioecious gametophytes.
• Tetrasporangia cruciate, in sori in the cortex of tetrasporophytes.
• Spermatangia forming more or less extensive patches on branches of male gametophytes.
• Female gametophytes bearing three-celled carpogonic branches, which, after fertilization, form bilocular cystocarps with median septum embedded in the thallus.

G. amansii.

• Plants forming dense tufts, reddish, rather rigid, cartilaginous, attached by a rhizomatous holdfast; erect thalli 10-30 cm tall, axis 0.5-2 mm wide, linear; branching pinnate or irregularly pinnate, in alternate or opposite manner, 4-5 orders, the upper portion usually with irregular ramification; branches and axes compressed at the lower part, 230-530 μm thick, and (sub)terete towards apices, with sharp and acute apices.
• Cross-section of branches showing a cortex of 1-4 layers of deeply pigmented small cells and a central part with rounded medullary cells; internal rhizines mainly outside the central tissue.
• Tetrasporangia on elongate-ovate or oblong-spatulate, claviform pedicellate branchlets.
• Cystocarps spherical and swollen, located beneath the apex of the branchlets.

G. australe.

• Plants forming expanded tufts, purplish-red, attached on substrate by prostrate rhizoidal branches; erect thalli up to 8 cm tall, main axis 0.7-2 mm wide near the base, 0.4-0.7(-1) mm wide above; branching pinnate; branches terete below and rather compressed toward the apices, not attenuate at the base, apex pointed; ultimate branchlets becoming gradually shorter on secondary axes so giving a pyramidal outline to frond.
• Cross-section of the axis showing rhizines profusely in inner cortex layers and rarely in the medulla.
• Tetrasporangia covering special clavate to tapering stichidia with a short to medium stalk.
• Cystocarps in terminal swollen portions of branchlets.

G. capense.

• Plants robust, bushy, up to 40 cm tall, several axes arising from a compact stoloniferous holdfast; dark brownish-red, texture tough cartilaginous.
• Axes several times pinnately branched, laterals opposite or alternate, not notably constricted at the base, especially when young markedly geniculate, inserted at relatively short intervals and overlapping each other.
• Axes compressed, up to 1.5 mm wide and about half as thick.
• Rhizines abundant, in younger branches in the central medulla, in older axes mainly concentrated in a subcortical layer.
• Tetrasporangial sori in slightly widened spatulate branch tips.

G. crinale.

• Plants forming expanded tufts, purple to yellowish-brown, attached to substrate by widely-branching rhizome; erect thalli cartilaginous, 2-7.5 cm tall; branching irregularly alternate to pinnate; branches terete or cylindrical below, less than 300 μm in diameter, and tapering upwards towards the apices.
• Rhizines usually aggregated in the inner part of the cortex.
• Tetrasporangia in flattened and spatulate branchlets.
• Cystocarps in enlargements of branchlets, usually solitary.

G. pulchellum.

• Plants forming dark red tufts, attached by clusters of branched rhizoids; erect thalli 2-10 cm tall, axes and branches terete, compressed or flat, the main branches broader than the laterals; branchlets often regularly or irregularly opposite.
• Tetrasporangia on flattened and elongated branchlets.
• Cystocarps in the central part of fusiform fertile branchlets, often with mucronate outgrowths.

G. pusillum.

• Plants small, solitary or forming extended mats, reddish-violet, prostrate axes cylindrical, attached on substrate by small peg-like haptera; erect thalli 0.5-2.4 cm tall, terete below and flattened above, 0.5-0.8 mm wide, sparsely proliferating; branching simple or irregular; internal rhizines congested between innermost cortical cells and outermost medulla cells.
• Tetrasporangia irregularly arranged in spatulate terminal ramuli.
• Carpogonia in terminal part of branches.

Growth and development

Growth of Gelidium in the wild has only occasionally been studied. In Indonesia, the growth of Gelidium in the wild seems relatively slow and heavily influenced by the season. The vegetative plants occur only in the period coinciding with the start of the rainy season. The success of vegetative growth is closely correlated with the success of their sexual reproduction and asexual propagation. The triphasic reproduction cycle of Gelidium is apparently similar to that of other red algae.

Ecology

Species diversity in Gelidium is generally higher in tropical latitudes than in temperate ones. In temperate latitudes the sizes of the fronds are larger, the species are ecologically dominant and often commercially viable. Typically, Gelidium spp. occur on rocky substrate, often on coralline crusts, associated with rapid water movement and arranged in successive belts that can extend down to 25 m depth. The general absence of commercial crops in tropical waters has not yet been explained (Indonesia and India are exceptions). There is still no comprehensive understanding of the many roles of water movement in the biology of these algae. In tropical waters, G. crinale and G. pusillum often inhabit the rocky intertidal zone, frequently extending into the subtidal waters. G. pusillum can occupy substrates under various ecological conditions and occurs also on sandy and muddy stony bottoms. A mat of small G. pusillum is often found on the roots of mangroves. It also occurs mixed with other small algae in rock spaces in the upper tidal zone. Most Gelidium including G. australe, G. capense and G. pulchellum, however, need rather strong currents, clear water and high salinity.

Phycoculture

Culture of Gelidium in tropical Asian countries has not been recorded, and at present all commercial crops of Gelidiales are presently from wild populations. Attempts to improve the natural production of Gelidium have been conducted on a small scale by spraying spores on rocks or artificial substrates, by settling spores on shells of molluscs, and by transplanting the plants. But so far the results have not been fully satisfactory and in field trials the Gelidium spp. are usually superseded by faster-growing seaweeds like Ectocarpus, Enteromorpha and Ulva spp. The same occurs with sporelings, which generally grow very slowly. These often also have to compete for space with sedentary animals, especially barnacles.

Diseases and pests

Gelidium plants are usually regularly grazed by fish and invertebrates, and are often heavily covered by epiphytes. A genus of parasitic red algae (Gelidiocolax N.L. Gardner) is specialized to grow in Gelidium spp.

Harvesting

Gelidium is harvested by hand, by cutting and scraping the alga from the substrate. Divers are often sent out to collect subtidal specimens. There are indications that scraping results in the destruction of creeping axes and may cause low recruitment and low regrowth. Cutting the seaweed, without damaging the holdfast, is considered to be necessary to retain harvestable populations. Gelidium that was washed up on the shore can also be collected, but the results are less predictable than from harvesting natural populations. Scientifically-based resource management programmes are needed to maintain maximum sustainable yields.

Yield

In Indonesia in 1989 6.5% of all Gelidium was harvested.

Handling after harvest

Gelidium seaweed collected for agar production must be dried as soon as possible to a moisture content of about 20%. The agar quality of dried Gelidium stays fairly stable during dry storage, even at tropical temperatures. To make traditional agar jelly, clean and fresh Gelidium is boiled in plenty of water for about an hour until all algal material has dissolved and a viscous colloid remains. Still, the colloid is sieved using fine-meshed textile. Sugar, flavouring (vanilla) and colour may be added to the colloid to improve taste. The last step is to let the colloid cool in containers at room temperature and form a firm gel. The gel is then cut into slices using metal wire, and sun-dried.

Prospects

The prospects for Gelidium are bright, but supplies are too dependent on natural stocks. While the culture techniques for Gelidium remain undeveloped, it is very difficult to compete with (often cultivated) Gracilaria as an agar resource.

Literature

• Akatsuka, I., 1986. Japanese Gelidiales (Rhodophyta), especially Gelidium. Oceanography and Marine Biology. Annual Review 24: 171-263.
• Hatta, M.A. & Prud’homme van Reine, W.F., 1991. A taxonomic revision of Indonesian Gelidiales (Rhodophyta). Blumea 35: 347-380.
• McHugh, D.J., 1991. Worldwide distribution of commercial resources of seaweeds including Gelidium. Hydrobiologia 221: 19-29.
• McHugh, D.J., 1996. Seaweed production and markets. FAO Globefish Research Programme 48. 73 pp.
• Melo, R.A., 1998. Gelidium commercial exploitation: natural resources and cultivation. Journal of Applied Phycology 10: 310-314.
• Santelices, B., 1991. Production ecology of Gelidium. Hydrobiologia 221: 31-44.
• Santelices, B., 1994. A reassessment of the taxonomic status of Gelidium amansii (Lamouroux) Lamouroux. In: Abbott, I.A. (Editor): Taxonomy of economic seaweeds 4. pp. 35-53.

Sources of illustration

Hatta, M.A. & Prud'homme van Reine, W.F., 1991. A taxonomic revision of Indonesian Gelidiales (Rhodophyta). Blumea 35: Fig. 8, p. 365 (details of G. pusillum var. pusillum); Santelices, B., 1988. Taxonomic studies on Chinese Gelidiales (Rhodophyta). In: Abbott, I.A. (Editor): Taxonomy of economic seaweeds with reference to some Pacific and Caribbean species. Vol. 2. California Sea Grant College Program, La Jolla, United States. Fig. 3, p. 95 (cystocarpic G. amansii), Fig. 5, p. 97 (habit G. crinale), Fig. 9, p. 102 (habit G. pusillum); Santelices, B., 1994. A reassessment of the taxonomic status of Gelidium amansii (Lamouroux) Lamouroux. In: Abbott, I.A. (Editor): Taxonomy of economic seaweeds with reference to some Pacific and Caribbean species. Vol. 4. California Sea Grant College Program, La Jolla, United States. Fig. 6, p. 42 (tetrasporic thallus of G. amansii). Redrawn and adapted by P. Verheij-Hayes.

Authors

• A.M. Hatta & R. Dardjat