What is Spirogyra?
One of the most common forms of free-floating freshwater algae is the spirogyra algae. One can find it on the surface of ponds, lakes, pools and other stagnant water sources. The word Spirogyra has been derived from two Greek words – Speria (meaning coil) and gyras (meaning twisted).
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Description
Spirogyra (genus Spirogyra) is a genus of over 400 species of free-floating green algae (division Chlorophyta) that can be found in freshwater habitats all over the world. Spirogyras are filamentous algae typically composed of slender unbranched chains of cylindrical cells and are recognized for their attractive spiral chloroplasts.
Before learning more about its shape and characteristics, let us take a look at its classification, which is crucial in understanding some of its traits which are mentioned later.
Spirogyra Classification
Now that you know more about the classification of spirogyra, learn about some of the primary traits shown by such algae.
Spirogyra Characteristics
Following are some of the Spirogyra Characteristics–
Ranging between two and ten, spiral-shaped ribbon-like chloroplasts exist inside them. Each chloroplast houses several pyrenoids.
Their bodies are characterized by multicellular filaments, which are present underneath a mucilaginous sheath.
Pectin and cellulose can be found on the cell walls of such algae.
Spirogyra Reproduction occurs asexually, sexually and vegetatively.
Spirogyra mostly exists in slow-running water bodies, such as ponds, pools and smaller lakes. One can identify it through the silky sheen that it gives off on the water’s surface.
Vegetative reproduction only occurs at lower temperatures. In all other conditions, sexual reproduction is the preferred method for fertilisation.
Before learning about its structure, check out this spirogyra diagram, where one cell has been magnified to point out its various parts.
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Image: Spirogyra Structure
Vegetative Structure of Spirogyra
Refer to the points below to assess the structure of spirogyra algae in its vegetative state.
Cells are green-coloured, un-branched filamentous and cylindrical shaped.
Basal differentiation is absent in free-floating species.
In sedentary species, basal differentiation may occur in the form of an attachment organ, called holdfast or haptera.
The cell walls have three distinct layers, and they are striated.
The outer layer is composed of pectose, while the other two cell wall layers are made out of cellulose.
Some species may show an additional yearly growth of cellulose in the cross wall, leading to the formation of replicate walls.
A granular, vacuolated protoplast exists as a thin lining inside cell walls. This layer is also known as the primordial utricle.
A tonoplast separates a vacuole from the cytoplasm surrounding it. This tonoplast is a semi-permeable membrane.
Before proceeding further, let us see how much you learned till now.
Spirogyra Reproduction
As stated previously, spirogyra undergo the process of reproduction via three process, namely, vegetative, asexual and sexual.
1. Vegetative Reproduction of Spirogyra
Fragmentation is responsible for the vegetative reproduction in such algae. The cell walls of two adjoining cells weaken and form fragments, which turn into filaments through their cellular division. In some cases, this filament breaks due to external injuries to the cell as well.
2. Asexual Reproduction of Spirogyra
It is present in only a few Spirogyra species. Asexual reproduction occurs when azygospores, akinetes, or aplanospores arise.
Aplanospores develop in the presence of unfavourable circumstances. The protoplast contracts and builds a protective wall around itself. Aplanospores are formed as a result of this.
Akinetes are nearly identical, but do have a stronger cellulose and pectin cell wall.
Akinetes and aplanospores are non-motile spores that, just after parent filament decays, grow into a new filament within ideal conditions.
Parthenospores are another name for azygospores. These are the gametes that did not fuse during sexual reproduction and grew asexually into a new filament.
3. Sexual Reproduction of Spirogyra
In sexual reproduction, conjugation occurs between two morphologically identical gametes.
Each of these gametes is known as gametangium. One of them is motile, while the other is non-motile.
Sexual reproduction occurs through one of two types of conjugation – scalariform or lateral conjugation.
What is Scalariform Conjugation?
In scalariform conjugation, two filaments come together and subsequently lie together. You can compare the resulting structure to that of a ladder. Some characteristics of such Spirogyra Reproduction include–
Male and female gametes fuse together, leaving one of them empty and the other full of zygotes.
The fusion occurs through conjugation canals formed between the two cells lying next to each other during this reproduction.
Zygotes escape from the parent filament after the latter decays. After escaping, these zygotes germinate when conditions are favorable.
What is Lateral Conjugation?
In lateral conjugation of Spirogyra, neighboring cells act as male and female gametes, with conjugation tubes forming between cells of the same filament. There are two types of lateral conjugation:
Direct lateral conjugation, where a passage is formed between adjacent cells allowing male and female gametes to fuse.
Indirect lateral conjugation, where a conjugation canal is formed between cells containing male and female gametes.
The protoplast of Spirogyra acts as a gamete called aplanogametes, which are formed in gametangia at the end of the growing season. Zygospores, formed by the fusion of male and female gametes, are diploid and have a thick cell wall comprising three layers: exosporium, mesosporium, and endosporium.
Zygospores remain dormant until favorable conditions arise, upon which they undergo meiosis to produce four haploid nuclei, with only one surviving and the others disintegrating. The developing zygospore bursts open to form a germ tube, which then divides repeatedly by transverse division to develop into a new haploid filament of Spirogyra.
Life Cycle of Spirogyra
Spirogyra has three types of life cycles, the most prevalent of which are vegetative and sexual. However, the asexual cycle happens infrequently. Spirogyra does have a haploid life cycle, with haploid vegetative filaments representing a long gametophyte generation and diploid zygospores representing the short sporophyte phase. The thalloid vegetative filaments multiply through vegetative and sexual reproductions, while asexual reproduction occurs extremely rarely in the life cycle.
Conclusion
Spirogyra stands as a fascinating organism within the realm of biology, characterized by its unique classification, structural features, and reproductive strategies. Its classification as a filamentous green algae places it among the diverse organisms inhabiting aquatic environments worldwide. The distinctive spiral arrangement of chloroplasts within its cells is a hallmark characteristic, facilitating photosynthesis and contributing to its ecological significance. Understanding Spirogyra Reproduction, including its methods of sexual reproduction through conjugation and the formation of zygospores, provides insight into its life cycle and adaptation to changing environmental conditions. Overall, delving into the Spirogyra Information in this article enriches our understanding of the intricate dynamics of biological systems in aquatic ecosystems.
FAQs on Spirogyra
1. What is the Size of Spirogyra?
Spirogyra can range between 10-100 µm in width. They can go up to several centimetres in length.
2. Why is Spirogyra Considered Autotrophic?
Spirogyra contains chlorophyll, which they can utilise to conduct photosynthesis. Therefore, the ability of spirogyra to produce their own food is what classifies them as autotrophic.
3. What is the Primary Difference Between Lateral and Scalariform Conjugation?
Scalariform conjugation occurs between two filaments of cells lying side by side, while the lateral conjugation occurs between two adjoining cells. Additionally, scalariform conjugation is also known as a ladder conjugation since it forms a structure resembling a ladder. Lateral conjugation, on the other hand, forms a chain.
4. What is the Specific Condition for the Occurrence of Vegetative Reproduction in Spirogyra?
Vegetative reproduction primarily occurs only when temperatures fall. However, under normal or higher temperature conditions, spirogyra primarily follows a sexual reproductive system.
5. What is the role of Spirogyra in the ecosystem?
The role of Spirogyra in the ecosystem includes oxygen production, serving as a food source for aquatic organisms, providing habitat and shelter, nutrient cycling, and oxygenating water bodies.
6. Does Spirogyra grow in water?
Yes, Spirogyra grows in water, particularly in freshwater environments such as ponds, lakes, and slow-moving streams.
7. What does Spirogyra use for movement?
Spirogyra does not exhibit active movement but may gently drift with water currents due to its filamentous structure.
8. What is Spirogyra in real life?
In real life, Spirogyra is a genus of filamentous green algae commonly found in freshwater habitats worldwide.
9. Is Spirogyra helpful or harmful?
Spirogyra is generally considered helpful in aquatic ecosystems as it contributes to oxygen production, nutrient cycling, and biodiversity. However, excessive growth of Spirogyra, known as algal blooms, can sometimes lead to water quality issues and ecological imbalances.
10. Is Spirogyra a fungus or bacteria?
Spirogyra is neither a fungus nor a bacteria. It is a type of green algae belonging to the division Chlorophyta.
11. What is the scientific name of Spirogyra?
The scientific name of Spirogyra is itself, Spirogyra. It's a genus within the order Zygnematales, named for the characteristic spiral arrangement of its chloroplasts.
12. Is Spirogyra a colony?
Spirogyra typically forms dense mats or colonies composed of interconnected filaments, but it is not considered a true colonial organism.
13. Can Spirogyra live on land?
Spirogyra is primarily found in freshwater environments and requires water to survive. It cannot live on land as it depends on water for various physiological processes, including reproduction and nutrient uptake.
14. What is Spirogyra Reproduction?
Spirogyra primarily reproduces through conjugation, a process involving the exchange of genetic material between adjacent filaments. Specialized cells called gametangia develop at the filament tips, producing haploid gametes—small, flagellated male gametes (antherozoids) and larger, non-motile female gametes (oogonia). Conjugation occurs as conjugation tubes form between filaments, facilitating the transfer of male gametes to female gametes for fertilization. This results in the formation of zygospores, thick-walled structures containing diploid zygotes formed by gamete fusion. Zygospores remain dormant until favorable conditions trigger germination, leading to the development of new Spirogyra filaments through meiosis and cell division. This reproductive cycle ensures the perpetuation of Spirogyra populations in freshwater environments.
15. Write 5 Spirogyra Characteristics?
Unicellular Filaments: Spirogyra is a type of green algae characterized by long, unbranched, multicellular filaments composed of cylindrical, uninucleate cells.
Presence of Spiral Chloroplasts: The cells of Spirogyra contain spiral-shaped chloroplasts, which are responsible for photosynthesis. These chloroplasts impart a characteristic green color to the algae.
Freshwater Habitat: Spirogyra predominantly inhabits freshwater environments such as ponds, lakes, and slow-moving streams. It thrives in clean, nutrient-rich water bodies with abundant sunlight.
Reproduction by Conjugation: Spirogyra reproduces sexually through a process called conjugation, wherein adjacent filaments exchange genetic material through conjugation tubes, leading to the formation of zygospores.
Ecological Importance: Spirogyra plays a vital role in aquatic ecosystems by serving as a primary producer, contributing to oxygen production through photosynthesis, and providing food and habitat for various aquatic organisms.
