The Red Algae is the oldest type of the eukaryotic algae. Its scientific name is Rhodophyta and it belongs to the class Rhodophyceae. There are more than 7,000 species that are recognized in one of the largest phyla of algae, Rhodophyta. The algae get its name owing to the presence of a water-soluble red pigment which is known phycoerythrin. This pigment is present sufficiently to mask the chlorophyll, giving it a red color. However, despite their name, not all rhodophytes are red. The ones that have very little of this pigment are greenish or bluish in color. These come in various shapes including coral-like, crustlike, leathery, and some more.
- Habitat: Almost 50 species of red algae can be found in freshwater whereas the rest of them occur mostly in tropical marine environments. Numerous species are found 210-260 meters underneath the surface of the sea. The phycoerythrin enables the red algae to photosynthesize at these depths by absorbing the blue light which can penetrate the water. About 15% of red algae are parasites that transfer their nuclei into host cells and change them. Other Rhodophyta is extremophiles, for example, Cyanidium that lives in acidic hot springs at 55 degrees Celsius. Some marine species have adopted a parasitic lifestyle while some may be found on closely or more distantly related red algal hosts.
- Diversity: Red Algae can be classified into two classes – Florideophyceae and Bangiophyceae. Florideophyceae algae have numerous small chloroplasts and a complex life cycle whereas Bangiophyceae algae have lesser complex life cycles and have a single central chloroplast. Some examples of the species of Florideophyceae include Batrachospermum, Chondrus, and Corallina. Some examples of the species of Bangiophyceae include Porphyra, Bangia, and Cyanidium.
- Evolutionary History: Red algae has a complex life history that involves three stages of independent organisms to complete their life cycle. Most of the Rhodophycean members either show biphasic or triphasic life cycle patterns. It was discovered that when the species begin to release gametes, and when it was fused together upon the female it leads to release of spores. These spores then germinate into a smaller alga which is described as a separate genus because of its different appearance and ecology.
- Structure and Properties: Most of the coralline red algae contain calcium carbonate. These play a major role in building coral reefs. In light of their capacity to discharge calcium carbonate, red algae do not decay and have a superior preserved fossil record than numerous other algae. Fossils of red algae have been found in rocks as old as 500 million years. The plant body may be unicellular or multicellular. The cell wall comprises of external pectic and inward cellulosic layer. In multicellular structures, the cells have wall pits, through which cytoplasmic associations are kept up.
- Reproduction: Reproduction in red algae takes place in three different ways – vegetative, sexual and asexual. Vegetative reproduction takes place only in unicellular form. Sexual reproduction is of advanced oogamous types. Asexual reproduction takes place by monospore, neutral spore, bispore, carpospore, and tetraspore. Male and female gametophytes are often separate. The male gametophytes produce spermatia whereas the female gametophytes produce the carpogonial branch that further produces a terminal carpogonium. The contact between spermatia and carpogonia is made possible with the help of water movements or water currents. This is because of the fact that red algae lack motile sperm.
- Fossil Record: Sometime between 2006 and 2011, two kinds of fossil were discovered in the sedimentary rocks in Chitrakoot, central India. The presumed red algae lie implanted in fossil mats of cyanobacteria, called stromatolites, in 1.6 billion-year-old Indian phosphorite, which made them the oldest plant-like fossils ever found by about 400 million years. The earliest coralline algae also called the solenopores, are believed to exist from the Cambrian period.
- Uses: Red algae has many uses. Let’s take a look at some of them:
- It is the natural food for fish and other aquatic animals.
- Red Alga is the most significant commercial food in Japan. It is used as a chief ingredient (as a wrap) in the preparation of the famous dish, Sushi.
- Agar or agar-agar which is a jelly-like substance used in puddings and other dishes is derived from red algae.
- Red algae are a rich source of vitamins, minerals, calcium, magnesium, and anti-oxidants.
- Red algae are also helpful in regulation of blood sugar levels, lowering bad cholesterol, and promoting healthy circulation of blood in the body.
- Red algae are also known to provide the right nutrients to your body and make your skin glow, boost your immune system, and contribute to bone health.
Carrageenan that is derived from red algae is used in the manufacture of toothpaste, cosmetics, and other food items such as ice creams and chocolate milk.