Morphology, seasonal phenology and observations on some aspects of the life history in culture of Porphyra dioica (Bangiales, Rhodophyta) from Devon, UK

Abstract

A seasonal study of the blade phase of Porphyra dioica at its type locality, Sidmouth, Devon, UK, undertaken between June 1999 and May 2000 revealed that individuals were present in the middle and lower littoral zones all year. Field-collected specimens were vegetative (8%), or possessed male (40%) or female (47%) reproductive structures, or had both on the same blade (6%) but totally segregated by a distinct line. Mean wet mass of individuals was greatest in June and least in February. There were no significant differences between the wet mass of individuals with male or female gametangia. Mean frond length was greatest in June and least in February. Mean frond width was greatest in May and least in February. Reproductive sori were marginal and pale straw-yellow for male gametangia, cream to pale green in unfertilized female gametangia, and bright red to dark red-brown once fertilization had taken place. Male gametangia were found in packets of 64 [2 X 4 in surface view (SV)]. Individuals with female reproductive structures were distinguished by one or more of the following: gametangial mother cells, trichogynes, spindle-shaped cells or divided zygotosporangia in packets of 16 (2 X 2 in SV). The ratio of male to female reproductive structures on individual thalli throughout the 12 months was approximately 1:1. In culture, spores were released from blades with female reproductive structures in every month tested. Of those individuals that released spores, the percentage that germinated into a conchocelis phase ranged from 15 % in August to 78 % in April. Conchosporangia or neutral conchosporangia formed at 5°C short days (SD = 8:16 h light-dark cycle), 5°C long days (LD = 16:8 h light-dark cycle), 10°C SD, 10°C LD, 12°C day neutral (DN = 12:12 h light-dark cycle), 15°C SD, 15°C LD, 20°C DN, and 20°C LD, but the completion of the life history was not observed.