Asparagopsis taxiformis (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

1, habit of a female gametophyte; 2, detail of a male gametophyte bearing spermatangial clusters; 3, detail of a female gametophyte bearing a young fertile branch with a trichogyne; 4, detail of mature cystocarp with part of the pericarp removed; 5, detail of mature cystocarp showing section through the ostiole; 6, detail of the tetrasporophyte; 7, tetrasporophyte detail with tetrasporangia, and tetraspores in one of the sporangia starting germination or being released.

Asparagopsis taxiformis (Delile) Trevis.

Protologue: Nomencl. alg.: 45 (1845).

Family: Bonnemaisoniaceae

Chromosome number: 2n= unknown

Synonyms

• Fucus taxiformis Delile (1829),
• Asparagopsis delilei Mont. (1841),
• Falkenbergia hildebrandii (Bornet) Falkenb. (1901).

Vernacular names

• Philippines: bulaklak-bato
• China: haicai
• Japan: kagikenori.

Origin and geographic distribution

A. taxiformis is found in both the tropics and subtropics, and is common in all oceans. In South-East Asia it has been recorded in Burma (Myanmar), the eastern coast of Peninsular Malaysia, the Philippines and Papua New Guinea. Gametophytic plants are not recorded for Indonesia, although tetrasporophytes have occasionally been found there.

Uses

The gametophytic plants of A. taxiformis are used as human food and animal fodder. The alga is considered a delicacy, with penetrating flavour and taste and fragrance of iodine which develops when allowed to stand. It is an excellent source of protein. It is used for controlling goitre. It can also be applied as fertilizer.

Production and international trade

There are no known estimates of production of the gametophytic plants of A. taxiformis, which are used for food and medicine. In Hawaii hand-collected A. taxiformis is sold for prices that makes it one of the most expensive vegetables in the world.

Properties

A. taxiformis produces unique toxins, containing the noxious compound bromoform and many derivates, as well as several halogenated acetones, haloacetaldehydes, haloalcohols, haloketones and haloacetamides. This alga is therefore not usually eaten by herbivorous fish or by sea urchins. Humans should not consume it in large quantities. It has also antibiotic and antibacterial/antimicrobial properties.

Description

• Gametophytic thalli with feathery or plumose erect branches, up to 13 cm tall, greenish to reddish, arising from creeping stolons attached by rhizoids to solid substrates.
• Erect branches with central terete axis giving rise to densely arranged plumose branches at the upper 1/2 to 2/3 portion; plumose branches composed of numerous fine, delicate, branched, determinate branchlets, densely disposed around an axis; main axes consisting of a long central cell with bulbous base and two lateral axial filaments, forming the centre of the branchlets; central cell surrounded by an open space, partly filled with branched, smallcelled filaments; this open cylinder surrounded by 5-6 rows of tightly packed small, roundish cortex cells.
• Life cycle triphasic, diplo-haplontic and heteromorphic.
• Gametophytes dioecious; cystocarps subspherical or ovate, bright red, borne at the apices of short branchlets, surrounded by a pericarp; spermatangia covering more or less completely the summits of special, short, clavate branchlets.
• Tetrasporophytes forming dense clumps or pompons of up to 5 cm in diameter, consisting of irregularly branched thin filaments, attached to other algae by multicellular haptera; filaments polysiphonous, up to 50 μm in diameter, each segment with a narrow central cell and three pericentral cells; segments about as long as they are broad.
• Tetrasporangia globose, one per segment, about 40 μm in diameter and tetrahedrally divided, replacing one of the pericentral cells.

Growth and development

Both gametophytic and tetrasporophytic plants of A. taxiformis grow by means of dividing apical cells. Male and female propagational structures occur only rarely. Tetraspores in tetrasporophytes do not always divide meiotically; when they do they produce tetrasporophytes again. Fragments of tetrasporophytes often break off and can persist to form new plants.

Other botanical information

Tetrasporophytes of A. taxiformis are known as Falkenbergia hildebrandii, as has been proved by culture experiments in Japan. However, these tetrasporophytes cannot be distinguished on the basis of morphological characters from F. rufolanosa (Harv.) F. Schmitz, which is the tetrasporophyte of the temperate species A. armata Harv.

Ecology

Gametophytic plants of A. taxiformis occur on solid substrate on reefs or rocky shores exposed to moderately strong water movement. They often cover parts of upper surfaces of reefs and boulders and are not grazed by herbivores. Tetrasporophytic plants are usally entangled with other algae, both in sheltered and in exposed localities.

Propagation and planting

A. taxiformis is not grown in phycoculture.

Harvesting

A. taxiformis is only hand-collected from natural populations by wading or diving.

Handling after harvest

A. taxiformis should be washed well in cold freshwater, soaked for half an hour or overnight in freshwater, then, using a wooden mallet, salted lightly and the upper branches pounded. Entire plants should be rolled into a ball. They will keep almost indefinitely without refrigeration and small quantities can be used as required.

Prospects

Because of its toxic potential A. taxiformis may be less suitable as food but possibly is of interest as a source of fine chemicals, especially bromine-containing chemicals.

Literature

• Abbott, I.A. & Cheney, D.P., 1982. Commercial uses of algal products: introduction and bibliography. In: Rosowski, J.R. & Parker, B.C. (Editors): Selected papers in phycology II. Phycological Society of America, Lawrence, Kansas, United States. pp. 779-787.
• Burreson, B.J., Moore, R.E. & Roller, P.P., 1976. Volatile halogen compounds in the alga Asparagopsis taxiformis (Rhodophyta). Journal of Agricultural Food Chemistry 24(4): 856-861.
• Chihara, M. & Yoshizaki, M., 1972. Bonnemaisoniaceae: their gonimoblast development, life history and systematics. In: Abbott, I.A. & Kurogi, M. (Editors): Contributions to the systematics of benthic marine algae of the North Pacific. Japanese Society of Phycology, Kobe, Japan. pp. 243-251.
• Fenical, W.H., McConnel, O.J. & Stone, A., 1979. Antibiotics and antiseptic compounds from the family Bonnemaisoniaceae (Florideophyceae). In: Jensen, A. & Stein, J.R. (Editors): Proceedings of the International Seaweed Symposium 9. Science Press, Princeton, United States. pp. 387-400.
• Madlener, J.C., 1977. The seavegetable book. Clarkson N. Potter Publishers, New York, United States. 288 pp.
• McConnel, O.J. & Fenical, W.H., 1979. Antimicrobial agents from marine red algae of the family Bonnemaisoniaceae. In: Hoppe, H.A., Levring, T. & Tanaka, Y. (Editors): Marine algae in pharmaceutical science. Walter de Gruyter, Berlin, Germany. pp. 403-427.
• Moore, R.E., 1977. Volatile compounds from marine algae. Accounts of Chemical Research 10: 40-47.

Sources of illustration

Børgesen, F., 1919. The marine algae of the Danish West Indies. Vol. 2. Rhodophycaceae. Fig. 351-b, p. 335 (cystocarp); Chihara, M., 1961. Life cycle of the Bonnemaisoniaceous algae in Japan (1). Science Reports of Tokyo Kyoiku Daigaku, section B, 10: Fig. 16 f, p. 147 (tetrasporophyte detail with tetrasporangia and tetraspores); Hori, T. (Editor), 1993. An illustrated atlas of the life history of algae. Vol. 2. Brown and red algae. Uchida Rokakuho Publishing Company, Tokyo, Japan. Plate 117, p. 236 (all other parts except 7). Redrawn and adapted by P. Verheij-Hayes.

Authors

• G.C. Trono Jr