719

15(1): Cryptogams: Algae

Caulerpa lentillifera J. Agardh

Mus. Senckenb. 2: 173 (1837).

CAULERPACEAE

2n = unknown

Caulerpa kilneri J. Agardh (1873), Caulerpa longistipitata (Weber Bosse) Sved. (1906).

Seagrapes, green caviar (En). Indonesia: lelato. Philippines: ararusip, arurusip (Ilocano), lato (Visayan).

Caulerpa lentillifera is widely distributed in tropical areas of the Indian and Pacific Oceans. In South-East Asia it has been recorded in Thailand, Vietnam, Peninsular Malaysia, Singapore, Indonesia, the Philippines and Papua New Guinea.

Caulerpa lentillifera is mainly used in a raw vegetable salad. In the Philippines it is cleaned and washed thoroughly and eaten plain or garnished with sliced tomatoes, onions, sliced green mangoes and fish sauce or the salad is dressed with sweet-sour sauce, vinegar or lemon juice, often with salt or powdered black pepper to taste. Caulerpa lentillifera is a favoured species due to its soft and succulent texture. Specimens packed for export can be salt-preserved. As a medicine it has antibacterial and antifungal properties and is used to lower blood pressure and to treat rheumatism.

Caulerpa lentillifera is cultivated in about 400 ha of ponds in Mactan, Cebu Province (the Philippines) and production is estimated at no less than 4000 t fresh weight per year, with more than 90% being produced during the dry months. No recent statistics on the export of fresh Caulerpa are available; the export of 827 t of Caulerpa lentillifera is registered for 1982. Commercial aquaculture in the Philippines started in the early 1950s on the island of Mactan. In Japan commercial cultivation of Caulerpa lentillifera started in 1986 in the tropical waters of Okinawa Province. A one-year feasibility study has shown that 12—15 t of fresh Caulerpa lentillifera can be produced annually in a one-hectare pond. In the Philippines, the retail price in 1995 was P20/kg. Return on investment has been calculated at 15% during the first year and double this amount for the succeeding years.

Caulerpa lentillifera is a potential source of protein and shows haemagglutinic activity. It usually contains small quantities of terpenoids.

Plant stoloniferous, up to 10 cm tall; stolons branched, terete in cross-section, 1—1.5(—2) mm in diameter. Descending branches (pillars) with tufts of rhizoids arising at irregular intervals from ventral side of stolons. Fronds rather densely set, without stalks or with very short, naked lower section on the upright axis, usually less than 5 mm long and 1—2 mm in diameter, consisting of an irregularly branched or more often unbranched terete axis, completely and usually densely covered by subspherical or more or less clavate branchlets, 1—3 mm in diameter, placed on 5—8 longitudinal rows or more irregularly and imbricately placed, always supported by clearly constricted pedicels. Thalli holocarpic when fertile.

Sexual reproduction of Caulerpa lentillifera is believed to be similar to that of other Caulerpa, but has not yet been observed in South-East Asia. Sexual reproduction of these most probably holocarpic plants would result in empty outer walls that would disintegrate quickly.

Caulerpa lentillifera is generally found growing on sandy to muddy substrates on reef flats not exposed during low tides and where the water is generally calm. It may form extensive beds or meadows in exceptionally good habitats. The alga is stenohaline and cannot thrive in areas where salinity is less than 25l. Salinities lower than 30l already result in a loss of crop. Growth of natural stocks in habitats where water becomes brackish during the rainy season, or those cultured in ponds, is highly seasonal.

Caulerpa lentillifera is cultivated in the Philippines in ponds and open lagoons which are protected from strong waves. Initial stocking rate is 100 g/m² or 1000 kg/ha; the seedstock is planted on the pond bottom uniformly by burying one end of a handful of seedstock at approximately one metre intervals, using string as a guide. Broadcasting may also be used to seed the ponds. However, the seedstock is then not anchored to the bottom and may easily be carried away by waves, becoming concentrated in one part of the pond which results in patchy or uneven growth. Planting is therefore the more efficient method. When cultivated in open lagoons, the site should be shallow (0.3—0.5 m at lowest tide) with free-flowing water and the substrate must be muddy-loam. The area must first be cleared of seagrasses and other marine organisms. Branches are half-buried into the muddy substrate at 0.5 m intervals. In the wild Caulerpa lentillifera is highly seasonal, with peak production during the sunny dry months of the year. All year round production is, however, possible if a flow-through system is installed in the culture ponds to fully control their salinity level during the rainy season. In the ponds multiplication mainly takes place by fragmentation of thalli. Cage cultivation of Caulerpa lentillifera is undertaken in Okinawa (Japan). Multistage cylindrical cages are used for cultivation in the tropical waters of Yamaha Bay. Small bundles of thalli are tied to the middle of the floor of each stage of the cages, which are then hung in the sea. If the cultivation ground is too shallow for the cages to hang, mosquito nets with bundles of cut pieces tied at intervals of 0.5—1 m are laid on the bottom parallel to the currents.
The maintenance of good water quality, which can only be achieved through proper pond management, is dependent on the ponds being appropriately designed and constructed. The following are factors considered in the selection of farm sites: proximity to a source of unpolluted seawater supply, far from freshwater sources such as rivers and creeks, the level of the pond being at, or just a little above the low-tide level, protected from the direct effects of wind-driven waves which can easily erode and destroy the dikes; the substrate should be muddy-loam; very soft and deep muddy bottoms should be avoided; abandoned or non-productive fish ponds fulfilling the above criteria are preferred after some modifications. The pond should be divided into 0.5—1 ha areas. The smaller units should be laid out in such a way that a 'flow-through system' can easily be incorporated. Newly built ponds are usually acidic and require the addition of hydrated lime while old ponds usually require 0.5—1 t agricultural lime per hectare each year. The ponds are first drained to a depth of 0.3 m to facilitate planting.

After planting, the depth of the water should be adjusted to 0.5—0.8 m. Flooding should be done slowly, so that newly planted seedstock is not uprooted by the water currents. A practical guideline for maintaining the proper water depth in ponds, as practised by farmers, is to adjust the depth to a level so that the plants can be seen from the surface. Ideally, the pond water must be changed at least every other day to maintain adequate levels of nutrients. At the start of the growing period, however, the pond water should be changed every 3—4 days, avoiding strong currents which may dislodge the algae. The frequency of changes should be increased at about the third week.
A newly planted pond with Caulerpa lentillifera should be inspected after a few days and bare areas replanted to ensure uniform growth of the crop. Fertilizers may be applied when the stocks appear unhealthy, e.g. light green to yellowish. In open lagoons the Caulerpa plots are monitored regularly and the seaweeds and seagrasses are cropped to allow a lead-time for the Caulerpa to grow and successfully establish in the area.
Cages and nets require periodic cleaning. Since Caulerpa lentillifera is affected by salinity levels lower than 30l, the cages should be lowered to some depth below the surface (about 0.5 m) when a decline in surface salinity is expected, such as after heavy rainfall. Other seaweeds in the ponds or nearby area compete with Caulerpa lentillifera for nutrients, space and light, and should be weeded out. Bleaching of Caulerpa spp., seen as the occurrence of white empty husks of these algae, might be the result of reproduction, as all contents are used in the production of motile reproductive cells.

Bacterial contamination through domestic and industrial pollution can become problematic. Pesticides should only be applied during the seasons that no Caulerpa is cultured in the ponds, since otherwise the Caulerpa may become contaminated and unsafe to eat.

Harvesting of Caulerpa lentillifera may be undertaken two months (or more) after planting, depending on the growth rate of the crop. Harvesting takes place when the bottom of the pond is uniformly covered with Caulerpa. About 20—25% of the original crop should be left more or less uniformly spread or spaced on the pond bottom to serve as seedstock for the next crop. Depending on the amount of seedstock left and the growth rate of the plants, the succeeding harvests may be reaped at intervals of about two weeks or longer. Harvesting is done by uprooting the plants from the mud. These are placed in a wooden dugout or banca and are washed thoroughly in clean seawater to remove the mud, silt and other dirt. Partial harvesting is also practised in open lagoon cultivation so that enough stock is left for the next crop.

Caulerpa lentillifera harvested two months after planting is of high market quality, light grass-green, soft and succulent. Older crop, although higher in biomass, is of lower quality, tougher and with pale or colourless basal portions.

Harvested Caulerpa lentillifera is placed in baskets or clean polythene sheets for sorting to remove any remaining dirt and other material (epiphytes), washed thoroughly in clean seawater and all excess water is allowed to drip off prior to packing.
In Japan, fresh fronds of Caulerpa lentillifera are packed in 100—200 g packages. These will stay fresh for about 7 days if kept chilled and moist. If refrigerated (5—10°C) in bottles or tubular polythene bags with seawater it will remain fresh for about 3 months. Brine-cured or salted and dehydrated samples, when soaked in freshwater, swell rapidly and recover their original shape within several minutes. Therefore, when distributed in ready-to-eat packets, these seaweeds and their dressing should be packed separately.

The sustained local demand for Caulerpa lentillifera and the growing popularity of health foods in restaurants both locally and abroad have resulted in an increasing demand for this sea vegetable. Evidence for this increasing popularity is shown by the Japanese who used to import Caulerpa from the Philippines. They now have developed their own farming technology for Caulerpa lentillifera in Okinawa to meet the high demand in Japan. Local farmers will benefit more from this industry if they are also able to produce this seaweed during the rainy season.

Pérez, R., Kaas, R., Campello, F., Arbaut, S. & Barbaroux, O. (Editors), 1992. La culture des algues marines dans le monde [The culture of marine algae in the world]. Infremer, Plouzane, France. 614 pp.
Trono Jr, G.C., 1989. The pond culture of Caulerpa and its use as food. Applied Phycology 6: 1—3.
Trono Jr, G.C. & Ganzon-Fortes, E.T., 1988. The methodologies and economics of Caulerpa pond culture. In: Trono Jr, G.C. & Ganzon-Fortes, E.T. (Editors): Philippine seaweeds. Annex 6. National Book Store, Metro Manilla, The Philippines. pp. 311—321.
Trono Jr, G.C., & Toma, T., 1993. Cultivation of the green alga, Caulerpa lentillifera. In: Ohno, M. & Critchley, A.T. (Editors): Seaweed cultivation and marine ranching. Japan International Cooperation Agency, Yokosuka, Japan. pp. 17—23.

G.C. Trono Jr

Trono Jr, G.C., 2001. Caulerpa lentillifera J. Agardh. In: Prud'homme van Reine, W.F. and Trono Jr, G.C. (Editors): Plant Resources of South-East Asia No 15(1): Cryptogams: Algae. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea