Halimeda (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Halimeda cylindracea - 1, habit; 2, sagittal section through an outer portion of about the middle of a segment to show characteristics of the cortical utricles and the extent of development of the cortex; a portion of the medulla is also included; 3, surface view of the utricles of a mature segment; 4, the same of a basal (old) segment. H. incrassata - 5, habit; 6, sagittal section through a segment; 7, surface view of the utricles of a segment. H. macroloba - 8, habit; 9, sagittal section through a segment; 10, surface view of the utricles of a mature segment; 11, surface view of the utricles of a young segment. H. opuntia - 12, habit; 13, sagittal section through a segment; 14, surface view of the utricles of a segment.

Halimeda J.V. Lamour.

Protologue: Mém. montée: 186 (1812) ("Halimedea").

Family: Halimedaceae

Chromosome number: x= unknown

Major species and synonyms

• Halimeda copiosa Goreau & E.A. Graham, Bull. Mar. Sci. 17: 433, figs 1-10 (1967), synonyms: H. opuntia (L.) J.V. Lamour. f. hederacea E.S. Barton (1901), H. opuntia var. hederacea (E.S. Barton) Hillis-Col. (1959), H. hederacea E.S. (Barton) Colinv. (1959).

• Halimeda cylindracea Dec., Ess. classif. alg. calcif.: 103 (1842), synonym: H. polydactylis J.Agardh (1887); misapplied names: H. incrassata Harv. (1860), H. incrassata f. monilis E.S. Barton (1901).

• Halimeda discoidea Dec., Ess. classif. alg. calcif.: 102 (1842), synonyms: H. cuneata Hering f. digitata E.S. Barton (1901), H. discoidea var. platyloba Børgesen (1911), H. discoidea var. intermedia W.J. Gilbert (1947).

• Halimeda distorta (Yamada) Colinv., J. Phycol. 5: 33 (1968), synonym: H. incrassata f. distorta Yamada (1941).

• Halimeda fragilis W.R. Taylor, Pl. Bikini: 88, pl. 48, fig. 2 (1950).

• Halimeda gigas W.R. Taylor, Pl. Bikini: 84, pl. 44, fig. 2 (1950).

• Halimeda gracilis Harv. ex J.Agardh, Algern. syst.: 82 (1887), synonyms: H. gracilis var. opuntioides Børgesen (1911), H. gracilis f. laxa (E.S. Barton) E.S. Barton (1911), H. gracilis f. elegans Yamada (1941).

• Halimeda incrassata (J. Ellis) J.V. Lamour., Hist. polyp. corall.: 307 (1816), synonyms: Corallina incrassata J. Ellis (1768), Halimeda incrassata f. tridentata Duchass. ex J. Agardh (1887), H. incrassata f. gracilis Børgesen (1913).

• Halimeda macroloba Dec., Ess. classif. alg. calcif.: 118 (1841), synonym: H. macroloba var. ecalcarea Weber Bosse (1926).

• Halimeda macrophysa Askenasy, Forschungsreise Gazelle Bot., Alg.: 14, pl. 4, figs 1-4 (1888).

• Halimeda micronesica Yamada, Kogaku Nanyo 4: 121, fig. 15 (1941), synonyms: H. incrassata f. pusilla Barton (1901), H. orientalis W.J. Gilbert (1947).

• Halimeda opuntia (L.) J.V. Lamour., Hist. polyp. corall.: 308 (1816), synonyms: Corallina opuntia L. (1758), Fucus prolifer M. Blanco (1837), Halimeda cordata J. Agardh (1887).

• Halimeda simulans N. Howe, Bull. Torrey Bot. Cl. 34: 503-504, pl. 29 (1907), synonym: H. incrassata var. simulans Børgesen (1911).

• Halimeda taenicola W.R. Taylor, Pl. Bikini: 86-87, pl. 46, fig. 1 (1950).

• Halimeda tuna (J. Ellis & Sol.) J.V. Lamour., Hist. polyp. coral.: 309 (1816), synonyms: Corallina tuna J. Ellis & Sol. (1786), Halimeda platydisca Dec. (1842), H. tuna f. albertisii Picc. (1879).

• Halimeda velasquezii W.R. Taylor, Bull. Torrey Bot. Cl. 89: 176-177, figs 8-14 (1962), synonym: H. opuntia f. intermedia Yamada (1934).

Vernacular names

• There are many well-known Halimeda in Asia, but none have vernacular names.

Origin and geographic distribution

Most Halimeda are pantropical, and many of them are widespread in South-East Asia.

Uses

Halimeda is used as an antibacterial medicine and against diseases caused by fungi. There are records showing that metabolites from H. cylindracea, H. gigas, H. gracilis, H. incrassata, H. opuntia, H. simulans or H. tuna are active against the bacteria Bacillus subtilus and Staphylococcus aureus, while H. gracilis is also active against the fungus Candida albicans. The extracts of Halimeda are active against P-388 lymphocytic leukaemia and Ehrlich ascites tumour systems in mice. Some Halimeda are used as a vermifuge. The first and possibly only published recipe for Halimeda as food is a 17th Century report that it makes a good dish when mixed with vinegar, salt and oil.

H. tuna is used as animal feed and often forms the food source for the green turtle. H. macroloba is applied as a plant growth regulator. Many Halimeda are used as fertilizer, especially in leached acidic soils.

Properties

Extracellular deposits of aragonite (a form of CaCo₃) are found in Halimeda. The aragonitic skeletons contain about 1% MgCO₃ and 1.3% SrCO₃. Halimeda can thus be used as a source of carbonate. Extraction of whole thalli yields a crude fibre product containing xylose and glucose residues in a ratio of 10:1. Highly bioactive diterpenoids, including halimedatrial, have been found in many (but not all) Halimeda spp.

Description

• Plants erect, from a few mm to about 1 m long, generally bushy, often arising from a fibrous or bulbous holdfast, branched; branches with linear series of calcified segments; nodes uncalcified, flexible; segments moniliform, cylindrical or discoid, simple or lobed.
• Internal structure filamentous, coenocytic filaments closely parallel and indurated in the joints, loosely branched in the medulla of the segments and there laterally bearing special fascicles of branchlets, with terminal cells forming a continuous cortex; medullary filaments sometimes closed by wall thickening at forkings and at the base of the gametophores.
• Sexual reproduction by biflagellate gametes produced in large dark green globular to pyriform gametangia on stalks which are simple or branched, arising from node, segment or surface.

The above-mentioned 16 Halimeda species can be divided into 3 groups:

Plants commonly grown in sandy locations with distinct bulbous rhizoidal holdfast:

• H. macroloba: segments large, 29 mm × 40 mm, subcuneate to reniform;

• H. simulans: segments small, often imbricate, margins often cuneate or lobed;

• H. incrassata: segments small, lower ones often partly cylindrical;

• H. cylindracea: segments of the upper part of the plant cylindrical.

Plants usually epilithic with several small holdfast areas (less than 1 cm adhering in length), each consisting of a single segment not obscured by sandy particles, laterally spreading, forming large clumps, densely branched, often heavily calcified:

• H. distorta: segments 16 mm × 19 mm, often contorted;

• H. opuntia: smaller segments up to 7 mm × 11 mm, often somewhat contorted;

• H. gracilis: segments up to 9 mm × 15 mm, usually mainly in one plane.

Plants usually epilithic with a single holdfast formed by a single segment not obscured by adhering sandy particles:

• H. micronesica: basal segment flabellate;

• H. gigas: utricles large, more than 120 μm (thus can be seen with the naked eye), segments more than 30 mm long, calcification rather light;

• H. macrophysa: utricles large, more than 120 μm, segments up to 15 mm long, calcification moderate;

• H. copiosa, H. discoidea, H. fragilis, H. taenicola, H. tuna and H. velasquezii: utricles small, segments 6-30 mm long, calcification light to heavy. Microscopical characters are to be used for distinction.

Growth and development

Reproduction in Halimeda is holocarpic, thus the plants die after release of the gametangia.

Other botanical information

The taxonomy of Halimeda is complicated and not yet solved. Most probably, specimens occurring in the Indo-Pacific region belong to species which are different from morphologically similar species in the Atlantic Ocean.

Ecology

Halimeda algae occur from slightly below low tide to 80(-100) m depth. They occur in warm seas with temperatures of 20-25°C, and grow attached to rocks or other hard surfaces, or in sand, mud or other unconsolidated substrate. Some Halimeda such as H. tuna and H. velasquezii grow in regions of strong currents. H. opuntia sometimes covers about 90% of rock surfaces in shallow locations (0.3-0.5 m below low water level). Halimeda spp. are generally considered to be important reef builders, being the producers of large amounts of calcareous sand. The average mature specimen contains 8.5 g of calcium carbonate. H. macroloba is known to occur in brackish water as well as in the Red Sea, which has a salinity of 37-40‰.

Phycoculture

Although it is possible to grow Halimeda in the laboratory, both in seawater or in artificial seawater, Halimeda has not yet been used for aquaculture.

Harvesting

Halimeda is only hand-collected, often from material washed up along the coast.

Prospects

Halimeda, with its antibacterial properties and calcareous contents, can be used both directly as a fertilizer and soil conditioner, especially on acid soils, or as a source of liquid extract for horticulture and agriculture.

Literature

• Fenical, W. & Paul, V.J., 1984. Antimicrobial and cytotoxic terpenoids from tropical green algae of the family Udoteaceae. Hydrobiologia 116/117: 135-140.
• Hillis-Colinvaux, L., 1980. Ecology and taxonomy of Halimeda: primary producer of coral reefs. Advances in Marine Biology 17: 1-327.
• Kooistra, W.H.C.F., Calderón, M. & Hillis, L.W., 1999. Development of the extant diversity in Halimeda is linked to vicariant events. Hydrobiologia 398/399: 39-45.

Sources of illustration

Hillis-Colinvaux, L., 1980. Ecology and taxonomy of Halimeda: primary producer of coral reefs. Advances in Marine Biology 17: fig. 17, p. 38 (all surface views of utricles), fig. 20, p. 50 (all sagittal-sections); Trono, G.C. & Ganzon-Fortes, E.T., 1988. Philippine seaweeds. National Bookstore, Manila, The Philippines. Fig. 30, p. 51 (habit H. cylindracea), fig. 33, p. 55 (habit H. incrassata), fig. 34a, p. 56 (habit H. macroloba), fig. 36, p. 58 (habit H. opuntia). Redrawn and adapted by P. Verheij-Hayes.

Authors

• P.Y. van Aalderen-Zen