Table of Contents
What is Red Algae?
The phylum Rhodophyta includes red algae, which is derived from the Greek words rhodon which means “rose” and phyton which means “plant.” They have a red in colour due to the presence of accessory pigments such as phycoerythrobilin, phycocyaniobilin, phycourobilin, and phycobiliviolin in phycobillisomes, as well as the green pigment chlorophyll pigments (often, chlorophyll a).
They save their carbohydrate reserves in the form of Florida starch. They are thought to be among the first eukaryotic algae. With almost 7,000 species identified, the group could be the largest. Over 90% of red algal species are found in marine settings, with the remaining 10% found in freshwater and two species located in coastal caves. Rhodella, Compsopogon, Stylonema, Bangia, Porphyra, Porphyridium cruentum, Hildenbrandia, Nemalion, Corallina officinalis, Ahnfeltia, Gelidium, and other red algae species this are examples.
Red Algae Classification
Protista is one of the taxonomic kingdoms in the previous categorization framework, known as the five kingdom scheme. It’s made up of protozoa that look like animals, algae that look like plants, and slime moulds and water moulds that look like fungi. Protista is separated into multiple phyla as a result.
Euglenophyta, Chrysophyta (diatoms), Pyrrophyta (dinoflagellates), Chlorophyta, Phaeophyta, and Rhodophyta are the phyla that divide the plant-like or algal species. Recent research and findings, on the other hand, may lead to modifications in taxonomic ranks and the development of new classification systems.
Red Algae Characteristic
The presence of phycobilin accessory pigments such as phycoerythrobilin, phycocyanobilin, phycourobilin, and phycobiliviolin concentrated inside the phycobilisomes causes red algae to appear crimson or red in colour, as their name implies.
Chlorophyll a and d, – and -carotene, lutein, and zeaxanthin are among the pigments found. Floridian starch, a 1-4 branched glucose polymer spread throughout the cytoplasm, represents their carbohydrate reserve. The outside layer of their cell wall is made up of agarose and agaropectin, whereas the interior layer is mostly made up of cellulose.
The absence of flagella and centrioles is another distinguishing trait of red algae. They’re also used to make pit connectors and plugs. Following mitosis, the pit connections and pit plugs form during cytokinesis.
Red algae are the only ones with these structures. Cell-to-cell communication and/or symplastic transport are hypothesised to be aided by pit connections. Red algae can reproduce in two ways: sexually and asexually. The merger of gametes is the method of sexual reproduction. The male gamete, on the other hand, is not motile because it lacks a flagellum. It must be carried to the female gamete by a water stream.
Asexual reproduction is usually accomplished through the formation of spores, fragments, and propagules. Similar to other algal groupings, there is a generational cycle. Red algae, on the other hand, goes through three generations in a row. Two sporophyte generations may follow the gametophyte generation.
The first sporophyte is known as the carposporophyte (due to the production of carpospores), and the second sporophyte is known as the tetrasoporophyte (because to the production of tetrasopores). In a nutshell, the life cycle begins with the creation of male and female gametes in the gametophyte.
The merger of two gametes at the end of this phase results in the development of a diploid zygote. The zygote matures into a carposporophyte, which generates carpospores. The carpospore becomes a tetrasporophyte, which then generates spore tetrads. Tetrads become gametophytes when they germinate.
Tetrasporophyte generation can be skipped in some cases when the carposporophyte produces carpospores that germinate directly into thalloid gametophytes. From single-celled to multicellular, the shapes are varied. Many of them are marine species that can be found along the tropical, temperate, and cold-water coasts and continental shelf zones.
Red Algae Evolution
According to the endosymbiotic theory, a photosynthetic prokaryote was absorbed by an early eukaryotic phagotroph. The symbiosis between the two primitive living forms resulted in the prokaryote becoming an organelle within the eukaryotic cell, specifically a plastid. This event is thought to have triggered the evolution of autotrophic clades such as green algae, red algae, and glaucophytes. However, the red algae are thought to have been implicated in two endobiosis outbreaks.
A secondary event between an ancestral red alga and a eukaryotic heterotroph may have resulted in the diversification of algal species, resulting in the emergence of new clades such as Cryptophyta, Haptophyta, Alveolata, and the heterokonts.
Biological Importance of Red Algae
The ecosystem’s limestone-reef builders are red algae. A good example is coralline algae. They secrete calcium carbonate, which aids in the formation of coral reefs. Nori (Porphyra) and dulse (Palmaria palmata) are two species that are used in Asian and European cuisines, respectively. Some red algae (e.g. Gracilaria, Gelidium, Porphyra, Palmaria, and Euchema) are collected for the manufacture of agar and/or carrageenan products due to the cell wall component.
Red Algae Citations
Antitumor potential of carrageenans from marine red algae. Carbohydr Polym . 2020 Oct 15;246:116568.
Lectins from red algae and their biomedical potential. J Appl Phycol . 2018;30(3):1833-1858.
Red Algae-Derived Carrageenan Coatings for Marine Antifouling Applications. Biomacromolecules . 2020 Dec 14;21(12):5086-5092.