The red algae (Rhodophyta) are richly represented in marine environments from the tropics to the polar regions. They are readily distinguished by their color, the result of a unique combination of photosynthetic pigments, and by the universal absence of flagellated cells, an apparently ancestral condition. Most species are capable of sexual reproduction. The life cycle typically involves three generations or phases: a haploid sexual phase, a diploid phase that grows in a semi-parasitic fashion directly on the female plant, and a free-living diploid phase. It has been suggested that the triphasic life cycle and complex patterns of sexual reproduction and spore development that characterize nearly every family of red algae evolved as compensation for an inefficient fertilization mechanism in the absence of motile sperm. Some of the most elaborate reproductive structures are found in the Gigartinales, a large order currently containing about 40 families. The Gigartinales, like most red algae, are composed entirely of branched filaments in which the cells are linked by special structures called pit connections. These cellular connections can be specially stained and observed by light microscopy, and the stages of vegetative and reproductive growth thus followed cell by cell, event by event. Dr. Max Hommersand of the University of North Carolina is making comparative studies of growth and reproductive development in several problematic groups of Gigartinales, to determine consistent patterns that reflect taxonomic relationships. The morphological evidence obtained will be used to test hypotheses about the multiple origins of auxiliary cells and connecting filaments in relation to other taxonomic characters. Results obtained in this study will be used in revising the classification of these red algae and to determine evolutionary lineages among them.
