Cultured Aquatic Species Information Programme - Porphyra spp

Biological featuresPorphyraspp. appears on rocky shorelines throughout the world, including a few species in thetropics or at the poles. The greatest diversity is found in cold-temperate and boreal regions.Most species appear as winter or summer annuals.Porphyracan bear desiccation, so can live inthe highest, driest reaches of the intertidal zone.Porphyrathalli appear in nature as free-livingorganisms, and their microscopic filaments bore into calcium carbonate substrates such asoyster shells.Porphyrablades may be from circular to linear in outline, and from a fewcentimetres to over a metre in length. Their colour is also variable, from rose-pink in speciesthat live entirely submerged, to variously mottled reds, yellows, browns and greens inintertidal species. The life history ofPorphyrais complex. Its microscopic stage is diploid andcalled the conchocelis, which consists of filamentous branches. Under specific conditions thefilaments form swollen branches called conchosporangia that extrude their contents asindividual cells without walls - conchospores. Meiosis takes place in each conchospore, whichwill develop intoPorphyrathalli. In some species, monospores produced at thallus marginsreproduce the blades asexually. Spermatia and carpogonia are formed in packets at the blademargins. Spermatia attach and effect fertilization. The zygote then divides to form a packet ofdiploid cells, carposporangium. Diploid carpospores are released from the carposporangiumand form diploid conchocelis filaments again for over-summering.