Desmids

Desmids are unicellular, photosynthetic green algae belonging to the order Desmidiales, characterized by their striking symmetry and ornate shapes.​

Structure and Morphology

Most desmids consist of two semicells joined by a narrow bridge (isthmus) where the nucleus is located.​

Their cell wall is often highly ornamented, with patterns of granules, spines, or tubercles, and consists of two distinct layers.​

Each semicell contains a large, often complex chloroplast, frequently with pyrenoids for carbohydrate storage.​

Desmids display a wide variety of symmetrical, attractive forms—elongated, star-shaped, or rotund—making them distinguishable under the microscope.​

Habitat and Ecology

Desmids are most common in fresh, acidic, nutrient-poor waters, such as bogs and lakes, but can also be found in eutrophic and moderately saline environments.​

Their presence and species diversity are used as indicators of water quality and ecological status, due to their sensitivity to environmental changes.​

Movement and Metabolism

Desmids secrete mucilage from cell wall pores, forming a protective layer and enabling slow gliding movements toward or away from light sources.​

They have no flagella and rely on mucilage and environmental currents for movement.​

Reproduction

Desmids reproduce asexually by division at the isthmus; each semicell forms a new semicell creating two new individuals.​​

Sexual reproduction occurs via conjugation: two cells join, exchange nuclear material, and form a zygote which develops into a new desmid.​

Desmids are ecologically significant as primary producers in freshwater habitats and are noted for their beautiful, symmetrical microscopic forms.