Ulothrix

Ulothrix, classified within the kingdom Plantae, is a genus of filamentous green algae commonly found in freshwater habitats worldwide. This article delves into its definition, uses, ecological role, species diversity, and its significance within the algae kingdom.

Ulothrix: Definition and Characteristics

Ulothrix is a genus of green algae characterized by its filamentous structure, typically forming long strands or mats in aquatic environments. These algae are known for their green coloration, stemming from chlorophyll and other pigments that facilitate photosynthesis.

Uses of Ulothrix

In aquatic ecosystems, Ulothrix plays a crucial role as a primary producer, contributing to the food web by providing sustenance for herbivorous organisms. Additionally, some species of Ulothrix are studied for their potential industrial applications, such as biofuel production due to their high lipid content.

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Ulothrix in Algae Communities

Within the realm of algae taxonomy, Ulothrix belongs to the class Chlorophyceae, characterized by its chlorophyll-rich cells and a lack of flagella during vegetative growth. This classification places Ulothrix among a diverse group of green algae that thrive in various aquatic environments, from ponds to rivers.

Species of Ulothrix

The genus Ulothrix encompasses several species, each adapted to specific ecological niches and exhibiting variations in morphology and reproductive strategies. Common species include Ulothrix zonata, Ulothrix flacca, and Ulothrix implexa, each contributing uniquely to freshwater ecosystems.

Kingdom of Ulothrix

Taxonomically, Ulothrix is classified within the kingdom Plantae, indicating its phylogenetic relationship with other green plants. As such, it shares fundamental characteristics with terrestrial plants, such as photosynthetic capability and cellular structure.

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Ulothrix Habitat 

It is a green filamentous algae found in running fresh water. Ulothrix comprises about 30 species. The common species U. zonata occurs in cold water whereas U. flacca is marine. U. implexa occurs in esturies (where river meats the sea) as lithophytes. It is an autotrophic alga and the reserve food is starch. 

Ulothrix Structure

An unbranched filament, consisting of numerous cylindrical cells joined end to end. The filaments remain attached to some substratum by means of rhizoidal cell, i.e. showing distinction in base and apex. The basal cell is elongated and colourless known as holdfast while the uppermost cell is rounded. Every green cell is squarish or rectangular and consists of cell wall sorrounding the protoplast.

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Cell wall consists of two layers. Inner layer is made up of cellulose and outer layer is mostly made up of protopectin which is insoluble in water.

Due to presence of protopectin, Ulothrix filaments appear as wet threads.  In the centre of the cell is a nucleus and a girdle or ring shaped (U. zonata) or collar shaped chloroplast. One (U. rorida) or more pyrenoids are present in the chloroplast. A vacuole is present, surrounding it is a thin layer of cytoplasm (primordial utricle).

Ulothrix Reproduction 

The Ulothrix reproduces vegetatively, asexually as well as sexually. 

1. Vegetative reproduction : It takes place by fragmentation. In this process a filament divides into small parts. These smaller fragments grow and give rise to new filaments of Ulothrix.
2. Asexual reproduction : It takes place by the production of zoospores, aplanospores, hypnospores, akinetes and palmella stage.

• Zoospore formation : In favourable conditions, each cell produces zoospores except holdfast. Cytoplasm collects in the centre and divides into 2,4,8,16 or sometimes 32 segments. Each segment develops into biflagellate or quadriflagellate zoospores. Each zoospore is uninucleate, pear-shaped with thin cell membrane (zoospores not having cell wall). The zoospores are of 3 types :

Quadriflagellate macrozoospores : Usually 4 per cell.

Quadriflagellate microzoospores : Usually 8 per cell.

Biflagellate microzoospores : Usually 16-32 per cell. 

Read More: Sexual Reproduction

The zoospores come out into a vesicle, later on the wall disintegrates (forming a pore in lateral wall) and macro and microzoospores are liberated free and float in water. Microzoospores attach to substrate by their anterior ends while macrozoospores attach by their posterior narrow ends. After some time zoospores give rise to new individuals.

• Aplanospores : Sometimes contents of a cell separate from the cell wall to form one or more rounded aplanospore instead of zoospores. Their wall is thin and they are nonciliated. After liberation, they germinate to produce new plants. 
• Hypnospores : Under unfavourable conditions, the protoplasm is separated from cell wall and develops into a thick- walled structure, the hypnospore. On approach of favourable conditions, the hypnospore gives rise to new individual.
• Akinetes : During unfavourable cells of the filament develop into thick walled structures known as akinete. Under favourable conditions they give rise to new plants.
• Palmella stage : When there is shortage of water, filament lies on the moist soil, each cell divides and redivides with the result that some small rounded cells form a colony which is surrounded by mucilaginous substance which protects it from unfavourable conditions and does not allow it to dry. On the approach of favourable conditions, this mucilaginous substance dissolves and these cells either directly or through zoospores develop into new plants.

3. Sexual reporduction : It occurs at the end of growing season. Ulothrix is heterothallic. Sexual reproduction is of isogamous type. The gametes are motile and biflagellate. Except holdfast each cell of the filament can give rise to 64 to 128 gametes. These gametes are smaller than zoospores. On dehiscence of gametangium, the gametes come out in a bag like structure and float on water. When two gametes of (+) and (–) strain come together, they fuse and a quadriflagellate zygospore is formed which after floating for sometime on water, rests on the bottom of the pond. At this time, its four flagella disintegrate and a wall is formed surrounding it from all sides. After taking a rest for long period it divides meiotically and gives rise to 16 aplanospores or zoospores. These come out of the sac and give rise to a new plant of Ulothrix.