Rhodophyceae

The members of Rhodophyceae are the red algae. Their name comes from the red pigment r-phycoerythrin, which is so abundant in the body that it masks the other colours and gives the group its characteristic red hue.

Habitat

Most red algae are marine, and they are especially plentiful in warmer parts of the sea. They are remarkable for the range of depths they tolerate: some grow in the well-lit waters just below the surface, while others thrive at great depths in the oceans where very little light manages to reach.

Body organisation

The red thalli of most red algae are multicellular, and some of them have a decidedly complex body organisation.

Food storage

Red algae store their reserve food as floridean starch, a substance whose structure is very similar to that of amylopectin and glycogen.

Reproduction

• Vegetative reproduction usually happens by fragmentation.
• Asexual reproduction is by non-motile spores.
• Sexual reproduction is carried out by non-motile gametes and is oogamous. It is followed by complicated post-fertilisation developments.

Comparing the three classes of algae

The three classes of algae can be set side by side by their pigments, stored food, cell wall, flagella and habitat: