FAMILY: Bangiaceae
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NAME: Porphyra - Seaweed |
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Data provided courtesy of Aquaculture/Fisheries Center, University of Arkansas at Pine Bluff - (Dr. Peter Perschbacher) |
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DISTRIBUTION:
Porphyra is a sizeable genus of blade-forming red seaweeds. Its species appear on rocky shorelines throughout the world, although there are few species in the tropics or at the poles. The greatest diversity is found in cold-temperate and boreal regions. Most species are found in nature as winter or summer annuals, and many live in the highest, driest reaches of the intertidal zone. HABITS: Porphyra thalli appear in nature as free-living, easily visible thin blades (the phase that is harvested for nori) and as tiny, microscopic filaments that bore into calcium carbonate substrate. Porphyra blades may be anywhere from circular to linear in outline, and from a few centimeters to over a meter in length. The color is also variable, from rose-pink in species that live entirely species that live entirely submerged, to variously mottled reds, yellows, browns and greens in intertidal species. The actual size and color of any given specimen depends on the species, the position of the specimen in the intertidal or subtidal zones, the season, the prevailing weather, and other factors. Hence, blade size and color are poor taxonomic indicators. SPAWNING: The Porphyra life history is complex. To grow Porphyra (known in the trade by its Japanese common name, "nori") commercially (there are nori aquaculture industries in many places, especially Japan, Korea and China but also in the USA), one needs to know and be able to control this life history. The conchocelis phase is diploid. Under specific conditions of light quantity, light quality, daylength and temperature (the permissive conditions differ between species, and sometimes between strains of a species), the filaments form swollen branches ("conchosporangia") in which the cells, though still diploid, develop the plastid features of blade-phase cells (stellate plastid with conspicuous pyrenoid). These branches protrude from the substrate and eventually release their contents as individual wallless cells ("conchospores"). In some species, different environmental conditions will stimulate the asexual reproduction of theconchocelis via naked "monospores" produced at the tips of normal-width branches. Meiosis takes place in each conchospore after wall secretion and during initial rhizoid production, and usually the four meiotic products survive. Hence, the blades are haploid and chimeric. In some species, monospores produced at thallus margins reproduce the blades asexually. Blades arising from monospores are, of course, not chimeric. Specific conditions of light quality and quantity, daylength and temperature stimulate the production of gametes. Male gametes ("spermatia") are produced in packets at the blade margins and are released by dissolution of the margin. Female gametes ("carpogonia") are formed some ways back from the margin. A receptive surface ("trichogyne") protrudes from each carpogonium and through the surrounding matrix, to which spermatia attach and effect fertilization. The zygote then divides to form a packet of diploid cells (the "carposporangium"). Diploid "carpospores" are released from the carposporangium by dissolution of the blade margin. Germination of carpospores, to form diploid conchocelis filaments, is not dependent on the presence of solid calcium carbonate, but in nature, apparently, only those carpospores that do germinate on, and subsequently penetrate, this substrate avoid getting eaten by snails and other small marine grazers. GROWTH: Blades may reach 3 ft. in length and 1 foot long in about 7 - 8 months. USES: Certain species are edible - the reddish-black wrapping around sushi rolls consists of washed, chopped, pressed, dried and toasted Porphyra blades. These species are known variously as "laver" (England), "nori" (Japan, North America), "kim" (Korea), "sluckum" (First Peoples of the North American Pacific Northwest) and "karengo" (New Zealand). Porphyra is the focus of a billion-dollar aquaculture industry in Japan, Korea and the People's Republic of China. CULTURE: Erdschreiber medium (Mary Parke, pers. comm.): modified from the original Plymouth seawater recipe; general purpose marine medium for xenic cultures [for bacteria-free cultures see reprints in Rosowski & Parker (1971)]. Preparation: Prepare separate tubes to contain 0.2 g NaNO3/10 ml H2O and 0.03 g Na2HPO4.7H2O/10 ml H2O. Autoclave and store at 10 ° C. Erdschreiber solution: to 1000 ml of pasteurized, filtered seawater, add the following:NaNO3 stock solution 1 tube Na2HPO4.7H2O stock solution 1 tube vitamin B12 (15 x 10-6 g/100 ml H2O) 1 ml PIV metal solution 12 ml soilwater (GR+) supernatant 50 ml For marine algae that require salinities less than 30 ppt, the basic erdschreiber medium is combined with glass-distilled water prior to inoculating the new culture, such that 1/2-erdschreiber combines erdschreiber medium and distilled water 1:1; 2/3-erdschreiber combines erdschreiber medium and distilled water 2:1, etc.REFERENCES: Prentice-Hall. Broadwater ST, Scott JL, Garbary DJ. 1992. Cytoskeleton and mitotic spindle in red algae. In: Cytoskeleton of the Algae (Menzel D, ed.) p. 93. CRC Press.Butterfield NJ, Knoll AH, Swett K. 1990. A bangiophyte red alga from the Proterozoic of arctic Canada. Science 250: 104.
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