CHLAMYDOMONAS: CHARACTERISTICS, TAXONOMY, STRUCTURE, HABITAT - BIOLOGY - 2025

Chlamydomonas is a genus of biflagellate unicellular green algae, 10 microns (mm) in diameter, frequently found in ponds, wet soils, and drainage ditches.

The green coloration is due to the presence of chlorophyll in its structure, and its colonies can be so abundant as to color clear water green. Despite being a unicellular organism, it has quite complex structures that enable it to carry out all the basic processes for living.

Chlamydomona

The cells of Chlamydomonas species are regularly oval, sometimes pyriform; its movement being characteristic due to the presence of two polar flagella.

These microscopic algae have the ability to photosynthesize; additionally, they absorb nutrients from the medium through the cell membrane. When environmental conditions are favorable, they reproduce asexually (zoospores) and sexually (gametes).

Thanks to its motor capacity, it is one of the most studied microscopic organisms in biological research. It has been examined as a model for deciphering basic aspects of life: mobility of flagella, evolution of chloroplasts, responses to light stimuli, and genome sequencing.

characteristics

Chlamydomonas are unicellular organisms, characterized by the presence of two apical flagella. For their feeding, depending on the conditions of the environment, they are forced photoautotrophs or optional heterotrophs.

These species have a photosynthetic system similar to that of plants. Indeed, they have the ability to produce hydrogen using light as an energy source, carbon dioxide from the environment, and water as an electron donor.

On the other hand, they have ion channels that are activated by direct exposure to sunlight, as well as a photosensitive red pigment that guides mobility in the aqueous medium.

Taxonomy

Of the genus Chlamydomonas, around 150 species have been described. Chlamydiae belong to the Chlamydomonadaceae family, Order Volvocales, Class Chlorophyceae, Division Chlorophyta, of the kingdom Plantae.

The main species of the genus Chlamydomonas are C. reginae, C. reinhardtii, C. coccoides, C. braunii, C. caudata, C. pulsatilla, C. euryale, C. isabeliensis, C. parkeae, C. plethora, C. pulsatila, C. concordia, C. hedleyi, C. provasolii, C. epiphytica, C. globosa, C. gloeopara, C. gloeophila, C. mucicola, C. minuta, C. quadrilobata, C. noctigama and C. nivalis.

Structure

The cellular structure of Chlamydomonas is covered by a cell wall and a plasma membrane, composed of cellulose, mucilage and calcium carbonate deposits.

Chlamydomonas have a nucleus within a cup-shaped chloroplast. Inside it a solitary pyrenoid is located where the starch resulting from the photosynthetic process is produced.

In these species the presence of two flagella originating from a basal grain located in the cytoplasm is common. Towards the apical area, a red pigment (stigma) is observed, which is sensitive to light, which fulfills the function of guiding motility.

It has a chloroplast surrounded by a pair of membranes, inside which are arranged the thylakoids stacked in scarlet. Like two contractile vacuoles, located near the flagella, responsible for respiration and excretion.

Habitat

The various species of Chlamydomonas live in continental environments, mainly in natural ponds of fresh or brackish water, and in humid soils or epiphytes on other plants.

One of the characteristics of this alga is the diversity of the environment where it develops, from the underwater hot springs to the Antarctic ice sheet.

These algae thrive in extreme conditions, such as the absence of oxygen. In fact, they have the ability to break down the water molecule into oxygen and hydrogen, using oxygen for respiration and releasing hydrogen.

Indeed, these algae are adaptable in nature. Achieving development in the total absence of light, using organic salts as alternative sources of carbon.

Photorespiration

Photorespiration is a process that occurs in unicellular species such as green algae of the genus Chlamydomonas. In this process, oxygen (O) is used and carbon dioxide (CO ₂) is produced. In fact, it is a process similar to breathing.

Because it happens in the presence of light and the balance is similar to that of breath, it receives this name. Unlike respiration, in which energy is produced; In photorespiration, energy is not generated, but consumed.

Chlamydomonas have a photosynthetic system similar to that of plants, so they are able to produce hydrogen using carbon dioxide, sunlight as an energy source and water as an electron donor.

The photorespiration process is regulated by various factors such as environmental conditions and the development of microalgae colonies. Hence, it is directly related to the intensity of sunlight, the pH and the temperature of the medium.

Reproduction

Reproduction is a characteristic of living beings, and Chlamydomonas are characterized by having two reproduction cycles: one sexual and the other asexual.

In some unicellular organisms, sexual reproduction is not usual, since they live in favorable conditions, and it is enough for them to maintain the continuity of the species through asexual reproduction.

On the contrary, when conditions are adverse, they turn to sexual reproduction. In this way, the new genetic recombinations will guarantee them to successfully cope with the new environmental conditions.

Reproduction

Chlamydomonas are haploid single-celled organisms for most of their lives. During the sexual cycle, fertilization occurs through the union of two fertile cells of different strains, giving rise to a diploid zygote.

During the maturation process of the zygote, a thick covering is generated that allows it to remain dormant when conditions are adverse. Subsequently, the zygote divides by meiosis, forming four new flagellate gametes.

Reproduction

In asexual reproduction, mating does not occur, but a duplication of individuals by various mechanisms. The offspring of the species is guaranteed from a part of its body, which separates and grows until it reaches the particular size and shape.

The asexual reproduction cycle of Chlamydomonas derives from binary fission or bipartition. The protoplast breaks down to form two, four, and eight daughter zoospores, similar to the mother cell. Each new zoospore is endowed with a nucleus, cytoplasm, and flagella.

References

1. Chlamydomonas Algae (2016) Notes on Botany and Agronomy. National Polytechnic Institute. National Polytechnic Institute. Recovered at: docsity.com
2. Chlamydomonas (2017) Encyclopedia Britannica, Inc. The Editors of Encyclopaedia Britannica. Recovered at: britannica.com
3. Chlorophyta (2015) Biodiversity and Taxonomy of Cryptogamic Plants. Biological Sciences Faculty. Complutense University of Madrid. Recovered at: escala.bio.ucm.es
4. Cubas Paloma (2008) Chloropythas - Green Algae. Recovered in: aulares.net
5. López Amenedo, I. (2014). Alterations in the cellular physiology of "Chlamydomonas reinhardtii" exposed to heat stress.
6. Scott F. Gilbert (2003) Developmental Biology. 7th edition. Editorial Panamericana. ISBN 950-06-0869-3
7. Taxonomy for Chlamydomonas (2018) Biodiversity Information System. Recovered at: sib.gob.ar