Red algae are also known as Rhodophyta. They are basically marine in their habitat and are autotrophic. They do not have motile stage. They can be unicellular, filamentous or ribbon shape. Some of them are macroscopic. They are known as red algae due to their red color. Red color is provided by formation of Phycoerythrin. It absorbs mainly blue green wavelength which can reach deep in the water. Their cell wall is made up of phycocolloids which are made up of cellulose and pectic compounds mainly. Agar and funori are important phycocolloids. A few of the red algae have calcium carbonate crust over their wall and they give the appearance of coral. Chromatophores are the photosynthetic organelle. Their photosynthetic pigments are chlorophyll, carotenoids and phycobilins. The later are water soluble and can be of red or blue color. These are known as Phycoerythrin and Phycocyanin respectively. They store their food in the form of floridean starch. Reproduction occurs by sexual, asexual and vegetative methods. Vegetative reproduction involves fragmentation and regeneration. Asexual reproduction occurs by formation of variety of spores. In sexual reproduction the male sex organ known as antheridium gives rise to non flagellate male gamete referred as spermatium. The female sex organ is known as carpogonium which has receptive part known as trichogyne. Spermatia are carried to trichogyne by water current.
They are edible and provide food to domestic animals. Some of the species has antibacterial action and can coagulate blood. They also act as a source of bromine. The phycocolloid agar is used in making culture media. It is also used as a thickening agent. It is obtained from gelidium. Another phycocolloid funori is used as an adhesive. A phycocolloid called carrageenin is used as clearing agent and emulsifier.
