Hypnea (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Hypnea spinella - 1, main branch with loosely and irregularly arranged branches and branchlets. H. charoides - 2, detail of an indeterminate branch with branchlets; 5, tetrasporangial nemathecia on branchlets. H. boergesenii - 3, cross-section of a vegetative branch: medullary cells with lenticular thickenings in their cellwalls; 4, cross-section of a spermatangial branchlet with small spermatangia formed from modified outer cortex cells. H. pannosa - 6, tetrasporangial nemathecia on branchlets; 7, cross-section of a tetrasporangial branchlet with tetrasporangia; 8, longitudinal section of a cystocarp with developing carpospores inside a pericarp.

Hypnea J.V. Lamour.

Protologue: Essai Thalassioph.: 131-132 (1813).

Family: Hypneaceae

Chromosome number: x= unknown;H. musciformis: 2n= 10

Major species and synonyms

• Hypnea boergesenii Tak. Tanaka, Sci. Pap. Inst. Algol. Res., Fac. Sci., Hokkaido Imp. Univ. 2: 233-235, figs 6-8, pl. 53, fig. 1 (1941).

• Hypnea cenomyce J. Agardh, Spec. gen. ord. alg. 2 (2): 452-453 (1851) [1851-1863].

• Hypnea charoides J.V. Lamour., Essai Thalassioph.: 132, pl. 4 (= pl. 10), figs 1-3 (1813), synonym: H. divaricata auct. (1848).

• Hypnea cornuta (Kütz.) J. Agardh var. stellulifera J. Agardh, Spec. gen. ord. alg. 2(2): 449 (1851) [1851-1863], synonym: Chondroclonium cornutum Kütz.

• Hypnea musciformis (Wulfen) J.V. Lamour., Essai Thalassioph.: 131 (1813), synonym: Fucus muscoides Wulfen (1791).

• Hypnea pannosa J. Agardh, Öfvers. Förh. K. Sv. Vet. Akad. 4: 14 (1847), synonym: H. nidulans Setch. (1924).

• Hypnea spinella (C. Agardh) Kütz., Bot. Zeitung 5: 23 (1847), synonyms: Sphaerococcus spinellus C. Agardh (1822), Hypnea cervicornis J. Agardh (1851).

• Hypnea valentiae (Turner) Mont., in P. Webb & Berthel. Hist. nat. Iles Canaries 3, part 2, sect. 4: 161 (1841) [1839-1842], synonyms: Fucus valentiae Turner (1808-1809), Hypnea hamulosa (Turner) J.V. Lamour. (1813).

Vernacular names

General:

• Indonesia: paris, bulong jaja (Bali)
• Philippines: culot, sumon-sumon.

H. charoides

• Philippines: anen.

H. spinella

• Indonesia: bulong budur (Madurese), sasangan pasir (Bawean).

H. valentiae

• Philippines: kulot ti pusa, samo.

Origin and geographic distribution

Hypnea occurs in tropical seas all over the world and some species have also been recorded at higher latitudes. Several species occur regularly along the coasts of countries of South-East Asia.

Uses

Most Hypnea can be used as a source of carrageenan. They contain the growth hormone gibberellin. Several species are used in human food as salad, mixed with rice in Thailand, Indonesia and the Philippines, but also in the form of dried noodle-like sheets or as jellies. The instant noodle-like sheets prepared from Hypnea are used in Burma (Myanmar) as a dietary supplement to combat goitre, inhibit the progress of hypertension, ease insomnia, prevent stomach diseases, constipation and internal parasites in digestive tracts, to stimulate greater activity and promote longevity. The dried algae are also used as medicine (in Indonesia as an anthelmintic and also antibiotic, especially antifungal, and as an antitumor compound), as fertilizer and as animal feed. However, studies on antibiotic activity of especially H. musciformis have resulted in contradictory results in different parts of the world. H. musciformis is or has been used as a commercial carrageenan source in Burma (Myanmar), Senegal, Brazil and Florida (United States). In Burma, however, many small-scale factories have been closed because of market problems: the general public in that country prefers agar powder imported from neighbouring countries to the locally produced strips of carrageenan.

Production and international trade

In South-East Asia (except Burma) hand-gathered Hypnea is only used for local consumption, and sold fresh or dried.

Properties

Hypnea contains the amino acids phenylalanine, leucine, tyrosine, valine, alanine, glycine, aspartic acid, glutamic acid, serine, threonine, arginine and histidine. It also contains sulphated galactan and minerals (Ca, Fe, K, Mg, Na and smaller amounts of Cd, Cu, Mn, P, Pb and Zn). Although agar has been often cited as the prominent phycocolloid of Hypnea, it has repeatedly been shown that its cell walls only contain high quantities (15-48% of dry weight) of kappa carrageenan, mixed with some iota-type repeating units. In high concentrations gel strength is much better than that of standard agar and as fine as the best gelatins in the market. Gel strength (in g/cm²) differs considerably according to species and method: H. musciformis 12.5-49.5, H. spinella (as H. cervicornis) 282-530 without KC1 treatment and about 640 with KCL treatment, H. valentiae 600 when measured in a 1% phycocolloid solution treated with a 1% KC1 solution. Usually, addition of an 0.1% KC1 solution considerably increases gel strength in Hypnea.

In India rather high concentrations were measured of proteins, fat (70 mg/100 g dried Hypnea sp.) and vitamin C (8.6 mg/100 mg fresh Hypnea material) and in Pakistan fatty acids, sesquiterpene and sterol compositions have been investigated. Palmitic acid, a saturated fatty acid, was present in the largest quantities, while oleic acid was the major unsaturated fatty acid.

Description

• Thalli bushy, entangled, caespitose or spreading, attached to substrate by primary discoid holdfast, often creeping or descending branches with secondary holdfasts.
• Branches slender, terete or compressed with persistent uniaxial filament, surrounded by pericentral cells, pseudo-parenchymatous cellular medulla and inner and outer cortex layer, often with spinulose branchlets.
• Life cycle triphasic, diplo-haplontic and isomorphic, with dioecious sexual thalli.
• Tetrasporangia zonate, terminal on corticating filaments, forming nemathecia on swollen parts of special short lateral branchlets; carpogonial branches three-celled, laterally on inner cortical cells.
• Cystocarps each enclosed in hemispherical poreless pericarp.
• Spermatangia cut off in chains from outermost cortical cells in slightly or inconspicuously swollen parts of terminal branchlets or proliferations or both.

H. boergesenii.

• Thalli forming dense tufts, composed of somewhat erect branches up to 17 cm tall, brownish-green.
• Main branches percurrent, terete, tapering towards the apices, 410-800 μm in diameter, proliferous in upper portion, densely clothed with short, simple, acuminate lateral branchlets 300-400 μm long, or compound lateral branchlets 570-600 μm long, bifurcate or beset with short spinose projections.
• Axes and branches in cross-section with small central cell surrounded by 5-6 larger pericentral cells, many other large medulla cells (often with lenticular thickenings, also in walls of pericentral cells) and a rather abrupt transition to the much smaller cortex cells.
• Tetrasporangial sori on basal or middle parts of ultimate branchlets; tetrasporangia 50-62.5 μm × 20-25 μm.
• Cystocarps almost spherical, 500-600 μm in diameter, solitary or in small groups on branchlets.
• Spermatangia around basal part of ultimate branchlets, cut off from modified and elongate cortex cells; spermatia about 4 μm in diameter.

H. cenomyce.

• Thalli light to reddish-brown, intricate-caespitose at upper and lower parts, forming densely entangled, cushion-like mass, 5-8 cm tall, 500-1000 μm in diameter.
• Branching irregular in all directions; branches cylindrical, beset with numerous short and long slender spinous branchlets, often with small accessory attachment discs.
• Pericentral cells 4-6; lenticular thickenings in medullary cell wall absent.
• Tetrasporangia borne in nemathecia in lower or middle portion of ultimate branchlets, swollen.
• Cystocarps subcylindrical, 600-1000 μm in diameter, solitary or in small groups on branches and branchlets.

H. charoides.

• Thalli brownish to pale red, caespitose, loosely intricate in lower parts, 10-14 cm tall.
• Branching alternate; branches subcylindrical, 450-600 μm in diameter, principal axes percurrent, beset with short, spinous branchlets.
• Transverse sections of main axes and branches not always with distinct central cell.
• Medulla cells (with few lenticular thickenings) not much larger than inner cortex cells, thus cell transition gradual; outer cortex cells much smaller.
• Tetrasporangial nemathecia on ultimate branchlets, swollen.

H. cornuta var. stellulifera.

• Plant dark red to pale red, erect to caespitose, 5-16 cm tall, with or without percurrent axes.
• Branching freely alternate, lateral branch axes percurrent, tapering to the extremities, ultimate branchlets long or short; small stellate spinous processes of 3-6 rays, abundant, peltately attached and easily detached.
• Transverse-sections of axes and branches with small central cell surrounded by 4-5 much larger medullary cells and many other medullary cells, all without lenticular thickenings; cell transition to much smaller cortex cells abrupt.
• Tetrasporangia 50-57 μm × 21.5-28.5 μm, with small nemathecial swellings, encircling basal and middle parts of branchlets.

H. musciformis.

• Thalli very bushy, often entangled, texture somewhat fragile, fleshy, dull purplish-red or bleached.
• Erect branches 10-20(-50) cm tall, about 1-2 mm in diameter; main branches dividing several times, beset by numerous, short, divaricate ultimate branchlets 1-5(-10) mm long; tips of branches often elongate, naked, usually swollen, hooked (crozier-like), bearing a row of small ultimate branchlets on abaxial side; tetrasporic branchlets usually spindle-shaped, rostrate; cystocarpic branchlets divaricate.
• Cystocarps swollen.

H. pannosa.

• Thalli caespitose, greenish to purple, submerged living plants with brilliant blue iridescence; structure cartilaginous but brittle when alive, forming thick mats of intricating branches on rocky substrates.
• Branching irregularly, alternate-spirally to alternate-opposite, forming wide angles and rounded axils, without percurrent axis; branches terete to slightly compressed, 1.0-3.0 mm broad, dividing into short stubby spines at terminal portions of thallus.
• In transverse-sections of branches rather large central cell surrounded by 5-6 pericentral medullary cells and other medullary cells, all of about the same dimensions and without lenticular thickenings in cell walls; cell transition to the much smaller cortex cells rather abrupt.
• Tetrasporangia 30-58 μm × 12-26 μm, in saddle-shaped nemathecia at middle side of ultimate branchlets, at first on one side, later encircling the fertile part.
• Fertile branchlets 700-3000 μm × 400-650 μm.

H. spinella.

• Thalli soft to subcartilagenous in texture, light red to scarlet, forming small, 1.5-3 cm tall, compact tufts on rocks, without percurrent axes.
• Branching irregular in all directions; branches spreading, 300-500 μm thick, smaller branches spinelike, slender ones variable in length, commonly anastomosing, proliferations usually present, not abundant. "H. cervicornis" is a growth form, with longer (up to 7 cm tall), less entangled and no anastomosing branches.
• In transverse-sections of main axes and branches, distinct central cell surrounded by 5-6 large, irregularly ovoid cells with rather thick walls (up to 5 μm thick) and lenticular thickenings; cell transition to much smaller cells rather gradual.
• Enlarged tetrasporangial nemathecia borne at middle or tip of determinate branchlets, 150-1500 μm × 100-200 μm; tetrasporangia 28-44 μm × 12-22 μm.
• Cystocarps spherical, solitary or in small groups at base of terminal branchlets, 580-1075 μm in diameter.

H. valentiae.

• Thalli erect, up to 12 cm tall (outside South-East Asia larger, up to 50 cm tall), greenish-brown or purple, laxly alternate-spirally branched, often with distinct (percurrent) axis extending throughout entire thallus length.
• Branches terete, 680-2500 μm in diameter, loosely entangled at basal part, somewhat membranous in living condition; ultimate branchlets lateral, filiform, occasionally forked with acute tips, and oriented at right angles to main axis, short proliferations abundantly formed on axes and branches.
• In transverse-sections of main axes and branches distinct central cell surrounded by 6-8 large cells with lenticular thickenings in cell walls; cell transition to the much smaller cortex cells rather gradual.
• Nemathecia in the form of swollen bands, borne at middle, near base, or rarely near tip of ultimate branchlets and proliferations.
• Tetrasporangia 32-70 μm × 14-32 μm. Spermatangial sori 250-1500 μm × 150-450 μm; spermatia 2.5 μm in diameter.
• Cystocarps globose, 700-1300 μm in diameter.

Growth and development

There is no reliable information on seasonality and reproduction of Hypnea in South-East Asia, but in India, vegetative growth of H. musciformis increases from October-November, reaching a maximum in February. In Hawaii H. spinella (as H. cervicornis) needs just 3 months to grow to its adult size of about 7 cm. Growth rates of about 20%/day occurred regularly in artificial culture of H. musciformis in warm seawater. Hypnea spp. have been found in the Philippines with tetraspores in December and January and with cystocarps in February. Growth rates of several Hypnea spp. increase considerably when nitrate is added, but only when grown in bright light. In H. musciformis addition of nitrate and phosphate in bright light increases growth rates but the content of phycocolloids decreases (from 44.3-27.7% in some cases).

Other botanical information

H. cenomyce includes var. tenuis Weber Bosse and H. musciformis includes the varieties esperi J. Agardh and hippuroides (Kütz.) Weber Bosse. H. esperi Bory is probably different from the variety of the same name under H. musciformis. Recently, H. charoides and H. valentiae have been treated together as a H. charoides-valentiae complex because these two species cannot be differentiated. The occurrence of H. musciformis in South-East Asia is not well documented. In Japan most specimens formerly included under this name are now considered to belong to H. japonica Tan. Tanaka, because the numerous short proliferations, characteristic for H. musciformis, are lacking in these specimens.

Ecology

Most Hypnea spp. grow in shallow water near the shore in areas somewhat exposed to waves and surf. H. pannosa grows well on rocky, slightly wave-exposed areas at or near the margin of the reef. It forms luminescent clumps when seen underwater, usually lodged between coral rocks or in depressions.

Propagation and planting

Hypnea is not known in phycoculture, and thus is gathered from natural stocks. Cultivation of Hypnea from spores can be considered: both tetraspores and carpospores are potential "seeding" material. Cultivation with vegetative fragments on lines is also possible. Mixed farming with Eucheuma J. Agardh has been tested. Seasonality of the Hypnea specimens in these mixed cultures is coincident with poor growth of the Eucheuma thalli.

Phycoculture

In phycoculture experiments with Hypnea, attached thalli grow much better than free-floating ones. The differences in production between these two methods can be as large as 60-200%.

Diseases and pests

In Hawaii the introduced H. musciformis has become a pest, and is the host of the symbiotic red alga Hypneocolax stellaris Børgesen, which is able to reduce the growth rate of the Hypnea thalli by 40% (and in laboratory cultures even by 70%). The host alga is also grazed by amphipods (Gammarids) and sea-hares (Aplysia spp.). Sea urchins avoid grazing on H. cornuta.

Harvesting

The best harvest of Hypnea can be expected during the dry season.

Yield

The carrageenan content of Hypnea plants can be maximized by maturing for two weeks in tanks without additional nutrients. Usually, peak levels in carrageenan occur shortly after periods of rapid growth. The phycocolloid content of H. muscoides in Veravalk (India) increases gradually from October-November, reaches a maximum in March, then declines, showing rapid decomposition. No data are available for South-East Asia.

Handling after harvest

Hypnea is used fresh or dried and bleached.

Prospects

The high growth rate of Hypnea, its high content of kappa carrageenan and the quality of its gels make Hypnea feature prominently as one of the most promising carrageenan sources in the tropics, coming only second to "Eucheuma" in commercial significance. Hypnea can also be used as fertilizer, as antitumor medicine as well as an antibiotic, a muscle relaxant or as a source of peptides which can agglutinate animal and human erythrocysts. The prospects of farming the seaweed commercially seem promising, although optimum phycoculture methods have to be developed for reliable future supplies.

Literature

• Berchez, F.A.S., Pereira, R.T.L. & Kamiya, N.F., 1993. Culture of Hypnea musciformis (Rhodophyta, Gigartinales) on artificial substrates attached to linear ropes. Hydrobiologia 260/261: 415-420.
• Cheng, Y.-M., 1997. Species of Hypnea Lamouroux (Gigartinales, Rhodophyta) from Taiwan. In: Abbott, I.A. (Editor): Taxonomy of economic seaweeds 6. pp. 163-177.
• Dawes, C.J., 1987. The biology of commercially important tropical marine algae. In: Bird, K.T. & Benson, P.H. (Editors): Seaweed cultivation for renewable resources. Elsevier, Amsterdam, The Netherlands. pp. 155-218.
• Kapraun, D.F., Bailey, J.C. & Dutcher, J.A., 1994. Nuclear genome characterization of the carrageenophyte Hypnea musciformis (Rhodophyta). Journal of Applied Phycology 6: 7-12.
• Lewmanomont, K., 1997. Species of Hypnea from Thailand. In: Abbott, I.A. (Editor): Taxonomy of economic seaweeds 6. pp. 179-191.
• Masuda, M., Yamagushi, Y., Chiang, Y.M., Lewmanomont, K. & Xia, B., 1997. Overview of Hypnea (Rhodophyta, Hypneaceae). In: Abbott, I.A. (Editor): Taxonomy of economic seaweeds 6. pp. 127-133.
• Melo, V.M.M., Medeiros, D.A., Rios, F.J.B., Castelar, L.I.M. & Carvalho, A. de F.F.U., 1997. Antifungal properties of proteins (agglutinins) from the red alga Hypnea musciformis (Wulfen) Lamouroux. Botanica Marina 40: 281-284.
• Mshigeni, K.E. & Chapman, D.J., 1994. Hypnea (Gigartinales, Rhodophyta). In: Akatsuka, I. (Editor): Biology of economic algae. SPB Academic Publishing bv, The Hague, The Netherlands. pp. 245-281.
• Soe-Htun, U., 1998. The seaweed resources of Myanmar. In: Critchley, A.T. & Ohno, M. (Editors): Seaweed resources of the world. Japan International Cooperation Agency, Yokosuka, Japan. pp. 99-105.
• Xia, B. & Wang, Y., 1997. Some species of the genus Hypnea (Gigartinales, Rhodophyta) from China. In: Abbott, I.A. (Editor): Taxonomy of economic seaweeds 6. pp. 193-206.

Sources of illustration

Xia, B. & Wang, Y., 1997. Some species in the genus Hypnea (Gigartinales, Rhodophyta) from China. In: Abbott, I.A. (Editor): Taxonomy of economic seaweeds with reference to some Pacific and Caribbean species. Vol. 6. California Sea Grant College Program, La Jolla, United States. Figs. 4 & 5, p. 195 (H. boergesenii), fig. 7, p. 196 (H. spinella, as H. cervicornis J. Agardh), figs. 12 & 13, p. 198 (H. charoides), figs. 36, 37 & 38, p. 203 (H. pannosa). Redrawn and adapted by P. Verheij-Hayes.

Authors

• G.C. Trono Jr & P. Gronier