Bostrychia radicans (PROSEA)
Introduction |
Bostrychia radicans (Mont.) Mont.
- Protologue: Orb., Dict. univ. hist. nat. 2: 661 (1842).
- Family: Rhodomelaceae
- Chromosome number: 2n= unknown
Origin and geographic distribution
B. radicans is widely distributed in tropical and warm temperate waters, throughout the Atlantic Ocean, the Indian Ocean and the Pacific Ocean. In South-East Asia it has been recorded in Burma (Myanmar), Thailand (all coasts), Peninsular Malaysia, Singapore, Indonesia, Brunei, the Philippines, and northern Papua New Guinea.
Uses
References to the use of B. radicans as a food are scattered in the literature and may refer to this or other Bostrychia spp., but particularly to B. tenella (J.V. Lamour.) J. Agardh. Although B. tenella has been described recently as important for human consumption there are no detailed data to support this statement. Early references to both B. radicans and B. tenella (as B. binderi Harv.), being eaten either raw or boiled, noted that it was found intermixed with thalli of Catenella spp. and other algae associated with mangrove. Samples consisted mainly of Catenella spp., with other algae regarded as contaminants.
Production and international trade
No data on the production of B. radicans are available, but quantities growing in the wild would be insufficient to allow for major harvesting.
Properties
Members of the genus Bostrychia Harv. synthesize the sugar alcohols dulcitol and sorbitol, which act as compatible solutes (osmolites), allowing the algae to exist in regions of fluctuating and wide-ranging salinity. Although these compounds can be extracted, the process would not be commercially viable.
Description
- Thalli filamentous, prostrate with suberect branches, forming a low turf on the substrate, purple to brown; main axis indeterminate, 120-200 μm in diameter, up to 2 cm long, bearing determinate lateral branches 2-3 cm long with 1-2(-3) orders of alternate branching.
- Thalli attached by special holdfasts (cladohaptera), composed of rhizoids arising at the end of vegetative branches; main axis consisting of a polysiphonous axis with 2 tiers of pericentral cells per axial cell, (5-)7-9 pericentral cells per tier, in fertile laterals only 5 pericentrals per tier, not corticated.
- Life cycle triphasic, diplo-haplontic and isomorphic.
- Tetrasporangial stichidia subapical, on ultimate lateral branches, 800-1200 μm long, 120-140 μm in diameter, with 4-5 pericentral cells per tier, each forming a tetrahedrally dividing tetrasporangium of 50-80 μm in diameter and 2 cover cells.
- Gametophytes dioecious; cystocarps subapical, ovoid to globular, 300-500 μm long and 250-450 μm in diameter, with ostiole 35-50 μm in diameter; carpospores 100-125 μm long, 65-75 μm in diameter; spermatangial branches 200-500 μm long, 65-75 μm in diameter, with 4-5 pericentral cells per tier covered by small spermatogenous cells.
Growth and development
Tetrasporophytes of B. radicans are much more common than gametophytes. Growth of all Bostrychia spp. is by division of apical cells. The pericentral cells are separated later and each Bostrychia species has its own characteristic further division.
Other botanical information
The information on distribution, uses and properties is also largely applicable to B. tenella (synonym: B. binderi, a name that has long been considered to belong to a species that can be separated from B. tenella). The B. tenella/binderi complex differs clearly from B. radicans in its way of attachment. In B. radicans holdfasts (cladohaptera) are formed at the end of specialized vegetative branches, while in B. tenella the haptera are peripherohaptera, formed directly from peripheral and cortical cells on the ventral side of prostrate indeterminate axes.
Ecology
B. radicans is a tropical alga associated with mangrove vegetation, where it grows on the modified roots and bases of mangrove plants. In these habitats it grows in a characteristic mixed community with other species of Bostrychia and with Caloglossa J. Agardh, Catenella Grev. and Stictosiphonia Hook.f. & Harv. This community is characteristic of mangrove habitats and is generally referred to as the Bostrychia-Caloglossa association. The algae of this association do not appear to be heavily grazed and the algal production is assumed to enter the food web through detrital food chains. The relative contribution of algae to the overall productivity of the mangrove community is unknown. Many fish and crustaceans feed among the mangroves and this has implications for the drainage and the so-called "reclamation" of mangrove swamps in tropical regions, especially where there is a heavy reliance on inshore fisheries.
Propagation and planting
B. radicans is not grown in phycoculture.
Harvesting
B. radicans is only hand-collected from natural populations.
Handling after harvest
B. radicans is sold either for direct consumption, or dried and then used in salads after boiling water has been poured on to it.
Genetic resources and breeding
Crossing experiments with specimens from different localities but morphologically all belonging to B. radicans have shown that crossing barriers occur in some areas, but not in other regions.
Prospects
The medical application of B. tenella in reducing blood cholesterol levels may also be possible for B. radicans.
Literature
- Karsten, U., King, R.J. & Kirst, C.O., 1990. The distribution of D-sorbitol and D-dulcitol in the red algal genera Bostrychia and Stictosiphonia (Rhodomelaceae, Rhodophyta) - a -reevaluation. British Phycological Journal 25: 363-366.
- King, R.J. & Puttock, C.F., 1989. Morphology and taxonomy of Bostrychia and Stictosiphonia (Rhodomelaceae, Rhodophyta). Australian Systematic Botany 2: 1-73.
- Post, R., 1938. Zur Ökonomie des Bostrychietum [On the economy of the Bostrychietum]. Planta 28: 743-744.
- Tjon Sie Fat, L.A., 1976. Bostrychietum, plantengeografisch onderzoek over de Bostrychia-Caloglossa-gemeenschap, de algenformatie van de mangrovebossen [Bostrychietum, a plant-geographical study on the Bostrychia-Caloglossa association, the algal formation of the mangrove forests]. MSc. Thesis, Rijksherbarium, Leiden University, The Netherlands. 115 pp.
- Tseng, C.K. & Chang, C.F., 1984. Chinese seaweeds in herbal medicine. Hydrobiologia 116/117: 152-154.
- Zuccarello, G.C. & West, J.A., 1995. Hybridization studies in Bostrychia. 1: B. radicans (Rhodomelaceae, Rhodophyta) from Pacific and Atlantic North America. Phycological Research 43: 233-240.
Sources of illustration
Bostrychia radicans: Joly, A.B., 1965. Flora marinha do litoral norte do Estado de São Paulo e regiões circunvizinhas [Sea flora of the northern littoral of the State of São Paulo and neighbouring regions]. Boletim de Faculdade de Filosofia, Ciências e Letras, Universidade de São Paulo, Botânica 21: Fig. 626, plate 52 (without page numbers) (transverse-section of branch), Fig. 640, plate 53 (without page numbers) (plant with cystocarps); Tjon Sie Fat, L.A., 1976. Bostrychietum, plantengeografisch onderzoek over de Bostrychia-Caloglossa-gemeenschap, de algenformatie van de mangrovebossen [Bostrychietum, a plantgeographical study on the Bostrychia-Caloglossa association, the algae-formation of the mangrove forests]. Msc Thesis, Rijksherbarium, Leiden University, The Netherlands. Fig. 2, p. 14 (habit), Fig. 5, p. 17 (holdfast); Ugadim, Y., 1976. Ceramiales (Rhodophyta) from Paraná and southern part of São Paulo State (Brazil). Boletim de Botânica, Universidade de São Paulo 4: Fig. 62, p. 161 (tetrasporangial stichidium), Fig. 79, p. 165 (spermatangial branches). Redrawn and adapted by P. Verheij-Hayes.
Authors
- R.J. King