Caulerpa taxifolia (PROSEA)
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Introduction |
Caulerpa taxifolia (Vahl) C. Agardh
- Protologue: Syn. Alg. Scand.: 22 (1817).
- Family: Caulerpaceae
- Chromosome number: 2n= unknown. However, it has been suggested that inside thalli of C. taxifolia two kinds of nuclei occur: small ones with three distinct chromosomes and larger ones with many chromosomes. These observations suggest that small nuclei are haploid (n= 3) and large nuclei polyploid.
Synonym
Fucus taxifolius Vahl (1802).
Vernacular names
- Indonesia: rumput laut (general)
- Philippines: lukay-lukay.
Origin and geographic distribution
C. taxifolia is widely distributed in the tropical seas of the world and is also found in some subtropical waters, e.g. in south-eastern Queensland (Australia) and in the Mediterranean Sea where it has been introduced and is considered a pest. It is common in South-East Asia, and has been recorded in Burma (Myanmar), Thailand, Vietnam, Peninsular Malaysia, Singapore, Indonesia, the Philippines and Papua New Guinea.
Uses
C. taxifolia can be eaten raw in salad, but it is less in demand than C. racemosa (Forssk.) J. Agardh and C. lentillifera J. Agardh. C. taxifolia is frequently cultivated in aquaria for aesthetic purposes. It is also used as a medicine to lower blood pressure.
Production and international trade
C. taxifolia is only used locally.
Properties
There is much literature about the toxicity of caulerpin and other terpenoids in C. taxifolia, especially of the strains found in the Mediterranean Sea. It is cited as having antibacterial, antifungal, antitubercular and haemagglutinic activities.
Description
- Plant stoloniferous; tubular stolon 0.5-2 mm in diameter; rhizoid-bearing branches (pillars) at the lower part, at irregular intervals.
- Fronds 6-15 cm tall (in the Mediterranean Sea, however, giant specimens 85 cm tall have been found), often on cylindrical stalk (naked sections of the erect axis) 1-3 cm long and 0.3-1 mm in diameter; axis usually somewhat compressed, 1-2 mm wide, simple or only exceptionally irregularly branched; branchlets on very short stalks, pinnately arranged, opposite, closely approximated, mostly not overlapping, with parallel sides and slightly constricted at their bases, compressed, 3-10 mm long (3-10 times as long as broad), 0.5-1.7 mm wide and curved upwards, tapering gradually to acuminate apices, only occasionally bifurcate.
- Thalli holocarpic when fertile.
Growth and development
Plants of C. taxifolia living in shallow water are susceptible to environmental change and have irregular widths and a wavy outline resulting from discontinous growth. Growth is most probably semi-perennial: no single part of the thallus persists for more than a year, but the individual persists by means of indefinite vegetative development. Growth in aquarium culture can be fast, covering all substrates within a week. It is known as an invader in the Mediterranean Sea, where it forms extensive meadows with an extremely thick cover of large fronds. Sexual reproduction is supposed to be monoecious and holocarpic, but it has been suggested that in the Mediterranean Sea only male anisogametes have been observed.
Other botanical information
Morphological variation in C. taxifolia may appear due to differences in ecological conditions. Plants living on exposed to semi-exposed beaches have narrower, shorter and more closely packed branchlets than those living in estuaries and protected beaches. The distance between branchlets in plants living on exposed beaches is closer (sometimes even overlapping) than in the latter. Plants from deeper water (10-30 m) are often longer than those from shallow water, as are many individuals of the strains introduced in the Mediterranean Sea. In some cases specimens may develop short, wide pinnules which approach the morphology found in C. mexicana Sond. ex Kütz. The latter, however, is a separate species, although the mutual taxonomic difference has often been discussed.
Ecology
The favoured place for C. taxifolia in the tropics is shallow water (1-3 m deep) on semi-protected beaches with moderate current. It grows well on both hard substrate and on a sandy bottom, and sometimes occurs as a creeping epiphytic alga on calcareous algae or on living stony corals. Its known vertical distribution reaches to a depth of 30 m, in tropical areas, and as deep as 100 m in the Mediterranean Sea. Endocellular bacteria in the cell lumen of rhizoids of C. taxifolia have been shown to take up inorganic phosphorus and organic carbon and nitrogen from substrates and translocate nutrient products to the photo-assimilatory organs. This rhizoid uptake of nutrients provides an explanation for the successful growth of these large coenocytic organisms in oligotrophic tropical waters as well as in oligotropic situations in the Mediterranean Sea.
Propagation and planting
Propagation of C. taxifolia in aquaria and in the Mediterranean Sea is by vegetative fragmentation. Sexual propagation is known to take place in tropical areas, but its frequency has not yet been studied.
Phycoculture
Caulerpa culture is generally done in ponds. C. taxifolia frequently coexists in C. lentillifera ponds, but no attempt at monoculture has been made. C. taxifolia often develops in marine aquaria from "living stones" imported from tropical countries.
Diseases and pests
Some sacoglossan opisthobranch snails are specialized feeders on Caulerpa spp. Their possible role in biological control on the invasive strain of C. taxifolia in the Mediterranean Sea has been discussed, but the proposed biological control actions with introduced sacoglossan mollusc species have been discouraged.
Harvesting
For daily needs C. taxifolia is collected in the eulittoral zone at low tide. Afterwards the plants are cleaned of sand, mud and other debris. Only the fronds are consumed.
Handling after harvest
C. taxifolia is only used fresh.
Prospects
Because C. taxifolia is less preferred than other Caulerpa spp., its consumption is relatively low and its competitiveness in the market weak. The recent invasive activity of this alga in the Mediterranean Sea has generated much information. If its medicinal potential were better documented, the large biomass available in the Mediterrean Sea may become of use for public health.
Literature
- Anonymous, 1997. Dynamique d'espèces marines invasives: application à l'expansion de Caulerpa taxifolia en Méditerranée [Dynamics of the invasive marine species: application to the expansion of Caulerpa taxifolia in the Mediterranean Sea]. Acte de colloques, Académie des Sciences, Institut de France, Paris.
- Chisholm, J.R.M., Dauga, C., Ageron, E., Grimont, P.A.D. & Jaubert, J.M., 1996. 'Roots' in mixotrophic algae. Nature 381: 382.
- Meinesz, A., Benichou, L., Blanchier, J., Komatsu, T., Lemee, R., Molenaar, H. & Mari, X., 1995. Variations in the structure, morphology and biomass of Caulerpa taxifolia in the Mediterranean Sea. Botanica Marina 38: 499-508.
- Ribera, A., Ballesteros, E., Boudouresque, C.-F., Gómez, A. & Gravez, V. (Editors), 1996. Second International Workshop on Caulerpa taxifolia, Barcelona, Spain, 15-17 December 1994, Universitat de Barcelona. 457 pp.
Sources of illustration
Coppejans, E. & Prud'homme van Reine, W.F., 1992. Seaweeds of the Snellius-II Expedition (E. Indonesia): the genus Caulerpa (Chlorophyta-Caulerpales). Mededelingen van de Zittingen van de Koninklijke (Belgische) Academie voor Overzeese Wetenschappen 37: fig. 6, p. 681 (detail fronds); Hatta, A.M. Original drawing (habit). Redrawn and adapted by P. Verheij-Hayes.
- see also the genus page
Authors
- A.M. Hatta
