Ulva (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Ulva fasciata - 1, habit; 2, surface view of cells in upper part of the blade; 3, cross-section of the upper part of a blade; 4, longitudinal section of a basal part of a thallus. U. lactuca - 5, habit. U. pertusa - 6, habit; 7, cross-section of a fertile thallus with zoosporangia or gametangia (diagrammatic); 8, quadriflagellate meiozoospores; 9. female gametes; 10, male gametes.

Ulva L.

Protologue: Sp. pl.: 1163 (1753).

Family: Ulvaceae

Chromosome number: x= unknown; U. fasciata,U. pertusa: 2n= 18

Major species and synonyms

• Ulva fasciata Delile, Descr. Egypte, Hist. nat.: 297, pl. 58: fig. 5 (1813) [1813-1826].

• Ulva lactuca L., Sp. pl.: 1163 (1753).

• Ulva latissima auct. non L., Harv., J. Bot. (Hooker) 1: 155 (1834), synonyms: Ulva lactuca var. latissima sensu C. Krauss (1846), possibly also U. indica Roth (1806).

• Ulva pertusa Kjellm., Bih. Kongl. Svenska Vetensk.-Akad. Handl. (ser. 4) 33(1): 4-7, pl. 1, pl. 3: figs 1-8 (1897). Accepted name is now (2016): Ulva australis Areschoug (1854).

• Ulva reticulata Forssk., Fl. aegypt.-arab.: 187 (1775).

Vernacular names

• Sea lettuce (En)
• Indonesia: bulung lengas (Bali)
• Philippines: lumot, gamgamet, lablabig.

Origin and geographic distribution

Ulva comprises 30 species and is widely distributed in most regions of the world. In South-East Asia all Ulva spp. are known to occur in Singapore, Indonesia and the Philippines, while U. lactuca and U. reticulata have been recorded from almost all countries in this region, although rarely mentioned from Papua New Guinea.

Uses

Ulva is occasionally used in Indonesia (Bali) for animal feed. In Makassar (Sulawesi, Indonesia), however, the frequently occurring Ulva bloom is not used at all. In Malaysia and the Philippines these algae are used as human food (rich in vitamin E), medicine and as a vermifuge. In the Philippines they are also used as feed for fish and for stray pigs. These algae are also applied as an antimicrobial agent, an antipyretic and cooler (refreshing liquid), and for treatment of sunstroke. They are also applied as packing material to cover baskets of Caulerpa spp. during shipping and transport to market places and also by fish vendors to cover fish in shallow round baskets used for hawking. In coconut plantations it can be used as manure.

In Chinese herbal medicine Ulva "lactuca" is known as a treatment for urinary diseases and dropsy, as well as a treatment for boils.

Production and international trade

Ulva algae are not commercially grown. Occasionally they are collected from wild populations or washed up on beaches.

Properties

Ulva species in general contain (in g per 100 g fresh weight): water 18.7, protein 15-26, fat 0.1-0.7, carbohydrates 46-51, fibre 2-5 and ash 16-23. They also contain vitamins B1, B2, B12, C and E. U. fasciata contains (in g per 100 g fresh weight): water 15.5, protein 6, fat 1.1, carbohydrates 30.2, fibre 12 and ash 35.2. Cu and Pb contents (mg/g) are 8.2 and 8.3 respectively. Ash content in U. lactuca is recorded as 29.1% (dry weight). The high protein level and good digestibility of the carbohydrates make them an attractive source of fish feed, while their rapid growth makes them attractive for studies on biomass production. Comparative studies on bioconversion indicate that these algae are more readily digested and give a higher methane yield than Gracilaria spp. In experiments done in India a lipophilic fraction of the ethanolic extract of U. fasciata showed significant antiviral activity against Japanese Encephalitis Virus (JEV). The active compound was identified as erythro-sphinga-4,8-dienine-N-palmitate. The same alga has been shown to contain an active significant inhibitor of Semiliki Forest Virus (SFV), as well as other active antivirus compounds.

Description

• Plants first subfiliform, later expanding with marginally attached or substipitate blades.
• Blades plane or crispate, orbicular to elongate laciniate, consisting of two cell layers separated by gelatinous cell walls thickened both internally and externally.
• Cells with single chromatophores with one or more pyrenoids; nuclei solitary, becoming multinucleate at cell extension of elongate holdfast.
• Life cycle diplo-haplontic and isomorphic.
• Gametes and spores are formed in undifferentiated vegetative cells.

U. fasciata.

• Blades flat, often twisted, dark green, 5-30 cm × 1-10 cm, attached by a small holdfast; base of blade entire, irregularly lobed or divided from base into branching linear segments; segment margins undulate, ruffled, crenulate.

U. lactuca.

• Plants foliose, bright green or grass green; blades lanceolate to rounded, often with somewhat lobed and undulate margins, to 60 cm long or more, with glossy broad sheets, attached by a small disciform holdfast; membrane thick near base, with marginal portions somewhat thinner; cells polyhedral in surface view, arranged in linear rows.

U. latissima.

• As in U. lactuca, but blades shorter than broad, much expanded at maturity.

U. pertusa.

• Blades solitary, dark green, shiny, somewhat crisp in texture when fresh, attached by small disciform holdfast from which a thickened and decurrent base arises, commonly irregularly perforated, lobed to deeply cut in segments; transverse-sections at base of blade about 165 μm thick, but much thicker immediately above the base; cells in cross-section with distinctly thickened outer walls, with cell lumen 60-65 μm long and 3-4 times its width; chloroplasts limited to inner ends of cells; sections towards middle of blade thinner, about 100 μm thick, with cell lumina 40-43 μm long, about twice as long as wide.

U. reticulata.

• Blades flat, light to dark green, reticulate, with holes of various sizes, about 65 μm thick; in surface view cells rounded; cell lumina ovate, about 20 μm long; chloroplasts concentrated close to surface of blades.

Growth and development

Gametes and spores of Ulva are formed in undifferentiated vegetative cells. Ulva is known to have an isomorphic alteration of generations with meiosis just before formation of zoospores by the sporophytic generation. Gametophytes produce biflagellate gametes and the sporophyte produces quadriflagellate zoospores. Most Ulva species are isogamous but some are known to be anisogamous. Sexual reproduction is through dioecious biflagellate gametes, while asexual reproduction is by quadriflagellate zoospores. In some species cells in the centre of the blade produce reproductive spores/gametes, which after release of the zoids create distinctive holes or reticulations. In other species gametes and spores are formed in cells along the margins of the blades, resulting in whitish margins when the zoids have been released. Ulva spp. may also multiply vegetatively by growth of fragments accidentally detached from a thallus.

Growth rates of Ulva decline markedly during periods of nutrient limitation and during zoospore formation. The rapid growth rate is well explained by its favourable morphology for the uptake of nutrients and use of light.

Other botanical information

Most species of the genus Ulva are exclusively marine.

Ecology

Ulva spp. grow in a wide range of habitats, on rocks, especially on dead coral fragments in the intertidal or subtidal zones. Their size and form vary with changes in environmental factors. They can grow luxuriantly in water enriched by organic wastes. There is even a correlation between sewage pollution in coastal waters and abundant Ulva growth. These algae often become a problem for seaweed farmers because as an epiphyte they grow fast on rope or even on top of cultured plants.

Propagation and planting

Some Ulva spp. have successfully been propagated by tissue culture from fragments and protoplasts. Growth experiments in the laboratory and greenhouse cultures have resulted in selected strains for special research projects.

Phycoculture

In culture experiments Ulva has been used to study biomass yield, biodetectors and bioaccumulators.

Harvesting

Small quantities of Ulva are hand-collected by local people, mainly for animal feed.

Handling after harvest

Ulva is mostly consumed fresh or sun-dried.

Breeding

Culturing of Ulva is still in the experimental stage using natural "seeds" or selected strains.

Prospects

Future utilization of Ulva will be for human food and for pharmaceutical purposes, especially as antiviral agents.

Literature

• Kamat, S.Y., Wahidulla, S., d'Souza, L., Naik, C.G., Ambiye, V., Bhakuni, D.S., Goel, A.K., Garg, H.S. & Srimal, R.C., 1992. Bioactivity of marine organisms. VI. Antiviral evaluation of marine algal extracts from the Indian coast. Botanica Marina 35: 161-164.
• Polne-Fuller, M. & Gibor, A., 1987. Tissue culture of seaweeds. In: Bird, K.T. & Benson, P.H. (Editors): Seaweed cultivation for renewable resources. Developments in Aquaculture and Fisheries Science 16(9): 219-239.
• Sharma, M., Garg, H.S. & Chandra, K., 1996. Erythro-sphinga-4,8-dienine-N-palmitate: an antiviral agent from the green alga Ulva fasciata. Botanica Marina 39: 213-215.

Sources of illustration

Stegenga, H., Bolton, J.J. & Anderson, R.J., 1997. Seaweeds of the South African west coast. Contributions from the Bolus Herbarium 18: Plate 15, p. 94 (U. fasciata); Tatewaki, M., 1994. Ulva pertusa Kjellman. In: Hori, T. (Editor), 1994. An illustrated atlas of the life history of algae. Vol. 1. Green algae. Uchida Rokakuho Publishing Company, Tokyo, Japan. Plate 96, p. 194 (U. pertusa); Trono, G.C., 1986. Philippine seaweeds. In: Guide to Philippine flora and fauna. Vol. 1. Natural Resources Management Center, Ministry of Natural Resources and University of the Philippines. Goodwill Bookstore, Manila, The Philippines. Fig. 3, p. 210 (habit U. lactuca). Redrawn and adapted by P. Verheij-Hayes.

Authors

• W.S. Atmadja