Chaetomorpha (PROSEA)

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Plant Resources of South-East Asia Introduction

List of species

Chaetomorpha Kütz.

Protologue: Phycol. germ.: 203 (1845).

Family: Cladophoraceae

Chromosome number: x= unknown; C. antennina, C. linum: 2n= 36?, C. aerea: 2n= 12, 18

Major species and synonyms

• Chaetomorpha aerea (Dillwyn) Kütz., Sp. alg.: 379 (1849), synonym: Conferva aerea Dillwyn (1806).

• Chaetomorpha antennina (Bory) Kütz., Bot. Ztg. 5: 166 (1847), synonyms: Conferva antennina Bory (1804), Chaetomorpha media (C. Agardh) Kütz. (1849).

• Chaetomorpha crassa (C. Agardh) Kütz., Phycol. germ.: 204 (1845), synonym: Conferva crassa C. Agardh (1824).

• Chaetomorpha javanica Kütz., Flora 30: 773 (1847).

• Chaetomorpha linum (O.F. Müll.) Kütz., Phycol. germ.: 204 (1845), synonym: Conferva linum O.F. Müll. (1778).

Vernacular names

General:

• Philippines: ripripies, ririppus.

C. aerea

• Philippines: lumot.

C. crassa

• Philippines: cawat-cawat, kawat-kawat, kauat-kauat.

C. javanica

• Indonesia: lumut laut, sayur lompan, lumut kehur.

Origin and geographic distribution

Chaetomorpha is widely distributed both in seas and in brackish water all over the world. In South-East Asia C. aerea has been recorded in Malaysia, Indonesia and the Philippines (Luzon, Negros); C. antennina in Burma (Myanmar), Pacific coasts of Thailand, Malaysia and the Philippines (Luzon); C. crassa in the same countries, where it is more common. In Thailand C. crassa is common on both coasts, and it occurs also in Singapore, Indonesia, in many locations in the Philippines and Papua New Guinea. C. javanica has been recorded in Vietnam, Sabah (Malaysia) and Java and Ambon (Indonesia). Outside the area it is only found on Christmas Island and the Maldives. C. linum has been recorded in Thailand, the western coast of Peninsular Malaysia, Singapore, Indonesia (not common) and the Philippines (Luzon, Visayas).

Uses

C. aerea is used for human food and as feed for milkfish.

C. antennina is eaten as a salad in Malaysia, and also used as feed for milkfish. C. crassa can be used to make a gelatine-like sweetmeat. It is eaten raw as a salad in Sabah (Malaysia) and in the Philippines. It is also used as fish bait and as feed for milkfish.

These three Chaetomorpha spp. form important constituents of the thick mats of mixed filamentous green and blue-green algae, covered by many periphyton algae found in fish ponds. These algal mats are known as "lab-lab" in the Philippines, and as "kelekap" in Indonesia. Growth of these thick algal mats is a necessary condition for successful traditional milkfish cultivation. In most cases the milkfish mainly feed on periphyton algae, by grazing the epiphytes from the hosts; only mature fish also eat the green filaments. Slow growth rates of young milkfish might be the result of inhibition of the necessary alkaline protease trypsin in milkfish by a tryptic inhibitor from a Chaetomorpha sp. The Chaetomorpha species blamed for forming this tryptic inhibitor is stated to be C. brachygona Harv., one of the most common filamentous algae in milkfish ponds. The filaments of the unattached species have the same dimensions as those of the attached C. javanica.

C. javanica is collected by the Chinese in Ambon (Indonesia) during the dry season (August and September). After being soaked overnight in freshwater it is boiled and eaten with bacon. In Sabah (Malaysia) it is eaten dried or boiled. C. linum is used in the same way as C. aerea.

Production and international trade

In the Philippines both C. antennina and C. crassa are successfully grown in culture, usually in connection with milkfish cultivation.

Properties

Seasonal variation in the soluble polysaccharide content has been demonstrated in C. aerea. The polysaccharides mainly consist of D-galactose, L-arabinose and D-xylose and its ester sulphates. The cell walls of Chaetomorpha contain 5-10% protein, especially in the outermost layers. The "higher plant" sterol β-sitosterol is the major sterol in C. linum; this is peculiar because it does not occur in some organisms that are considered ancestral to higher plants. The major sterol in C. crassa is cholesterol. C. antennina contains antibacterial and antifungal compounds.

Description

• Plants filamentous, unbranched, unattached or attached by a cylindrical basal holdfast cell; all cells large and highly multinucleate, usually with firm lamellose walls.
• Life cycle haplontic or isomorphic diplo-haplontic and dioecious.
• Asexual quadriflagellate zoospores and sexual biflagellate isogametes formed in separate slightly enlarged cells in the filaments.

• C. aerea. Plant gregarious, 10-30 cm tall, light or dark green, attached by slender, subclavate basal cell with disk-like base, lobed or fimbriate at the margins; basal cell at the top, 7.5-10.5 mm long, and 2.5-4.2 times as long as the suprabasal cell, 130-150 μm in diameter; filaments slender towards the base, more than 150-300(-500) μm in diameter, stiff, the cells 1-2 mm long, slightly constricted at the septa. Zoospores in the upper cells of filaments, cask-shaped to subglobose, 600-700 μm in diameter.

• C. antennina. Tuft up to 7 cm tall, attached; each basal cell up to 5 mm long, about 0.1 mm in diameter, with annulate base and attached to the substrate by branched rhizoidal filaments; vegetative cells with thick striated walls, 400-600 μm long and 200-350 μm in diameter.

• C. crassa. Plant entangled; filaments (300-)500-550(-700) μm in diameter, dark green; cells about as long as broad, but occasionally up to 2 mm long, with thick walls.

• C. javanica. Strand-like tuft, attached; each basal cell rhizoidal, clavate, about 250 μm long, 37-70 μm in diameter; upper cells 30-125 μm long, 55-100 μm in diameter, walls thick and lamellate.

• C. linum. Plant composed of loosely entangled, unattached filaments, yellowish-green, somewhat stiff and curled, cylindrical or the cells slightly swollen, (0.75-)1-2(-5.0) mm long, 100-375 μm in diameter.

Growth and development

The unbranched filaments of Chaetomorpha grow quite quickly by intercalary growth. The largest upper cells, however, usually soon form spores or gametes and disintegrate rapidly. The sexual biflagellate isogametes normally fuse to form a zygote, but they can also function as zoospores and germinate to form new haploid filaments.

Other botanical information

All cells of Chaetomorpha filaments are coenocytic, thus each compartment contains many nuclei.

Ecology

Chaetomorpha spp. are free-living organisms as well as epiphytes and they also often grow on rocks, boulders, corals and (fragments of) shells. C. aerea grows attached to rocks, especially under ledges, in exposed, even surf-beaten locations. This alga is fairly resistant to environmental stress, such as high temperatures, extreme fluctuations in salinity (euryhaline) and desiccation due to lowering of water level. C. antennina occurs attached to rocks and shell fragments in the lower intertidal to upper subtidal areas, often in shallow rock pools and lagoons, C. crassa in exposed as well as sheltered conditions in intertidal and shallow subtidal areas, and is often entangled with other seaweeds or seagrasses. C. javanica forms tufts on rocks, walls and dead coral, while C. linum forms entangled masses with other macroalgae in shallow water.

Dense accumulations (mats) of Chaetomorpha reduce the oxygen level in water overlying sediments. This reduced condition induces the release of phosphorus from the sediments, which may result in higher productivity of algal mats in fish ponds. Chaetomorpha does not grow well on acidic sulphate-enriched soils.

Propagation and planting

Optimal growth of Chaetomorpha mats in artificial fish ponds can be promoted by careful reclamation of the ponds. It is especially important to reclaim and ameliorate the acidic sulphateenriched soils in mangrove areas to avoid iron, aluminium and manganese toxicity. With proper reclamation P-fertilization might make the production of the algal mats much higher than that in less well reclaimed ponds.

Phycoculture

Chaetomorpha is only grown as part of algal mats in milkfish cultivation.

Harvesting

Chaetomorpha is grazed by milkfish. It is hand-collected for use as a salad.

Handling after harvest

Chaetomorpha is mainly used fresh.

Prospects

Chaetomorpha will probably be a lasting component of the natural algal mats in traditional fish ponds. The role of the different Chaetomorpha in trypsin deficiency in young milkfish has to be studied in more detail. This may result in experiments to manipulate the species composition of the natural algal mats.

Literature

• Benitez, L.V., 1984. Milkfish nutrition. In: Juario, J.V., Ferraris, R.P. & Benitez, L.V. (Editors): Advances in milkfish biology and culture. Island Publishing House Inc., Metro Manila, The Philippines. pp. 133-143.
• Lavery, P.S. & McComb, A.J., 1991. The nutritional eco-physiology of Chaetomorpha linum and Ulva rigida in Peel Inlet, Western Australia. Botanica Marina 34: 251-260.
• Singh, V.P. & Poernomo, A.T., 1984. Acid sulfate soils and their management for brackish water fishponds. In: Juario, J.V., Ferraris, R.P. & Benitez, L.V. (Editors): Advances in milkfish biology and culture. Island Publishing House Inc., Metro Manila, The Philippines. pp. 121-132.

Authors

• P.Y. van Aalderen-Zen