Gracilariopsis lemaneiformis (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

1, habit; 2,3, portions of apical branches; 4, cross-section of a thallus; 5, longitudinal section of a thallus; 6, longitudinal section of a cystocarp; 7, longitudinal section of the pericarp of a cystocarp; 8, cross-section of a tetrasporophyte with tetrasporangia; 9, cross-section of a male gametophyte with spermatangial sori of the Chorda-type.

Gracilariopsis lemaneiformis (Bory) E.Y. Dawson, Acleto & Foldvik

Protologue: Beih. Nova Hedw. 13: 59 (as "lemanaeformis") (1964).

Family: Gracilariaceae

Chromosome number: 2n= unknown

Synonyms

• Gigartina lemaneiformis Bory (1828, as "lemanaeformis"),
• Gracilaria lemaneiformis (Bory) Grev. (1830, as "lemanaeformis"),
• Gracilariopsis sjoestedtii (Kylin) E.Y. Dawson (1949).

Origin and geographic distribution

G. lemaneiformis occurs in the tropical to warm-temperate parts of all oceans. In South-East Asia it has been recorded in Thailand, Vietnam, Indonesia and the Philippines.

Uses

G. lemaneiformis is one of the useful marine red algae for agar extraction.

Properties

In Japanese samples the viscosity of 1.5% agar of G. lemaneiformis diminished from 220-380 cP in non-alkali treated material to almost zero after alkali treatment, while mean gelling temperature (about 55 °C) and mean melting temperature (about 90 °C) of 1.5% agar did not change much after alkali treatment. Gel strength for non-alkali treated Japanese samples (1.5% agar) was 440-685 g/cm², rising to 2000-2125 g/cm² after 7-10% alkali treatment. For material from Indonesia and China, both after 5% alkali treatment, gel strength values of 880 and 848-872 respectively have been recorded. Hardness (about 250 g/mm²) of 1.5% agar of Japanese samples of G. lemaneiformis after alkali treatment (7-10% NaOH) is the highest of all commercial Gracilarioid agars that have been tested, while flexibility values of 2.5-9 g/100 mm² have been recorded for these same samples. Agar of G. lemaneiformis is especially interesting because it retains its gel strength with the addition of even 75 g/100 ml of sugar in a 1% agar solution, resulting in a very elastic gel. Most Gracilaria agars are not sugar-reactive.

Description

• Thalli solitary to caespitose, slender, dark green to brownish or red, up to 40 cm tall with distinct main axis and few to several long branches; branching irregular to alternate, mostly from lower portion, many thalli arising from a spreading holdfast; branches simple, cylindrical, long, filiform, slightly constricted at branch bases, 0.5-2.0 mm in diameter; branchlets 2-5, frequently occurring from a single branch apex.
• Fronds in transverse section consisting of medulla of large thin-walled (3-8 μm) cells, 115-700 μm in diameter, with two layers of cells in cortex; transition of cells from medulla to cortex abrupt.
• Tetrasporangia ovoid to ellipsoidal, embedded in slightly modified cortex of anticlinally elongated cells.
• Spermatangia superficial, continuously over the frond surface.
• Cystocarps spherical, 0.7-1 mm in diameter, with or without a short beak, constricted at the base or not, taller than diameter of bearing branch; gonimoblast of small cells, no absorbing filament; pericarp 116-182 μm thick, with undifferentiated cells.

Growth and development

Plants of G. lemaneiformis from warm areas in South-East Asia (the Philippines, Thailand) are not as robust as those from the type locality (Peru) and other countries where surface seawater temperatures are slightly cooler. Moreover, tropical plants frequently have a percurrent, filiform axis with few to many short laterals, short-spinous to elongate. In temperate areas, the laterals may be as elongate and as thick as the axes, with few laterals of the second order, or they may be bushy plants.

Ecology

G. lemaneiformis grows on sand or mud or in sandy-muddy areas of the intertidal zone with clear water and sheltered areas not exposed during low tide. In Thailand, it is found growing on fish cages.

Propagation and planting

Methods of propagation and planting for G. lemaneiformis are the same as those for Gracilaria, thus often by broadcasting in shallow, semi-enclosed ponds, although fixed-bottom monoline cultivation as well as culture on rafts are also practised.

Phycoculture

In China the floating culture method may be suitable for G. lemaneiformis. In Indonesia a study showed that this alga has a better potential for artificial cultivation in pond or field areas than other seaweeds.

Harvesting

Harvesting techniques used for G. lemaneiformis are the same as those for Gracilaria, thus mainly hand-collecting.

Yield

Agar yield for G. lemaneiformis varies from 20-27% of dry weight for non-alkali treated material from Japan, increasing to about 34% after treatment within 2 hours with 7-10% NaOH at 80°C. For material from Indonesia, agar yield of about 10% has been obtained after treatment with 5% NaOH.

Handling after harvest

Post-harvest techniques for G. lemaneiformis are the same as those used for Gracilaria: after washing the seaweed should be dried immediately, packed in bags and stored in a dry place.

Prospects

As a useful source of agar, G. lemaneiformis may have good prospects for phycoculture development.

Literature

• Abbott, I.A., 1994. New records and a reassessment of Gracilaria (Rhodophyta) from the Philippines. In: Abbott, I.A. (Editor): Taxonomy of economic seaweeds 4. pp. 111-118.
• Lewmanomont, K., 1994. The species of Gracilaria from Thailand. In: Abbott, I.A. (Editor): Taxonomy of economic seaweeds 4. pp. 135-148.
• Rebello, J., Ohno, M., Ukeda, H. & Sawamura, M., 1997. Agar quality of commercial agarophytes from different geographical origins: 1. Physical and rheological properties. Journal of Applied Phycology 8: 517-521.

Sources of illustration

Abbott, I.A. & Hollenberg, C.J., 1976. Marine algae of California. Stanford University Press, Stanford, California, United States. Fig. 433, p. 497 (habit, as Gracilaria sjoestedtii); Dawson, E.Y., 1949. Studies of northeast Pacific Gracilariaceae. Allan Hancock Foundation Publications, Occasional Paper 7: plate 16, p. 87 (portions of branches and longitudinal-section of thallus, as Gracilariopsis sjoestedtii), plate 17, p. 89 (spermatangia, as Gracilariopsis sjoestedtii); Xia, B. & Zhang, J., 1999. Flora algarum marinarum sinicarum, vol. 2, Rhodophyta, 5. Academiae Sinicae Edita, Beijing, China. Fig. 34, p. 57 (cross-section of thallus, sections of cystocarps and tetrasporophytes, as Gracilaria lemaneiformis). Redrawn and adapted by P. Verheij-Hayes.

Authors

• K. Lewmanomont & S.-M. Phang