STUDIES ON THE LIFE CYCLE OF PORPHYRA DIOICA AND PORPHYRA UMBILICALIS FROM PORTUGAL

Abstract

Pereira, R.1,2, Sousa‐Pinto, I.1,2 & Yarish, C.3 1Centre for Marine and Environmental Research, Rua do Campo Alegre, 823, 4150‐180 Porto, PORTUGAL; 2Botany Dept. of the University of Porto; 3University of Connecticut, Dept. of Ecology and Evolutionary Biology, 1 University Place, Stamford CT 06901‐2315, USAPorphyra is a well known genus, as it is one of the most important maricultured seaweeds. It has an annual retail value of US $1.8 billion principally grown in Japan, Korea and China. In the past 10 years, expanding markets in North America and Europe have put new demands on the import of the red alga. After some attempts trying to grow Asian species, efforts are now centered on domestication of native species, both in North America and Europe. With our current understanding of this genus, we believe that their are at least six Porphyra species along the Portuguese coastline. We have initially identified two species, P. dioica and P. umbilicalis, as potentially promising for aquaculture development. We are studying the life cycles and phenology of these species, with special note on morphological variability and on the environmental control of each phase of the life cycle. Porphyra dioica carpospores germinate best at 15‐20°C and 25‐75 micro mol photons m‐2 s‐1. Best conditions for conchocelis vegetative growth and the development of conchosporangia are at 15° C and 25‐75 micro mol photons m‐2 s‐1. P. dioica conchocelis growth appears to be under temperature controlled, rather than by photoperiod. For P.umbilicalis, 15° C and 25 micro mol photons m‐2 s‐1 are the best conditions to obtain conchocelis and for formation of conchosporangia. At these conditions carpospore survival rate is about 33.4 %. Conchospores are released at 10 and 15° C and at 25‐75 micro mol m‐2 s‐1. For both species, formation of conchosporangia seems to be more related with time and culture conditions, rather than with size or development of the conchocelis.