Stramenopiles

Stramenopiles, also known as Heterokonts, are a major line of eukaryotes that include a wide variety of organisms, such as algae, protozoa, and fungi-like organisms. They are characterized by the presence of two distinct types of flagella, one of which is smooth and the other is covered with tripartite tubular hairs, known as mastigonemes.

Characteristics

Stramenopiles are distinguished by their unique flagellar structure. The anterior flagellum is typically covered with tripartite tubular hairs, while the posterior flagellum is smooth. This feature is a key diagnostic trait of the group.

Stramenopiles exhibit a wide range of forms and lifestyles. They can be unicellular or multicellular, autotrophic or heterotrophic, and they inhabit a variety of environments, from marine to freshwater to terrestrial ecosystems.

Major Groups

Diatoms (Bacillariophyceae)

Diatoms are a major group of algae and are among the most common types of phytoplankton. They are unicellular and are known for their intricate silica cell walls, which form a variety of beautiful and complex shapes.

Brown Algae (Phaeophyceae)

Brown algae are a large group of mostly marine multicellular algae, including many seaweeds of colder Northern Hemisphere waters. They are known for their brown color, which results from the presence of the pigment fucoxanthin.

Oomycetes

Oomycetes, also known as water molds, are a group of fungus-like organisms. They are important decomposers in aquatic ecosystems and include some notorious plant pathogens, such as the causative agent of the Irish potato famine, Phytophthora infestans.

Golden Algae (Chrysophyceae)

Golden algae are mostly unicellular, biflagellate algae found in both freshwater and marine environments. They are named for their golden-brown color, which is due to the presence of carotenoid pigments.

Ecological Importance

Stramenopiles play crucial roles in their ecosystems. Diatoms, for example, are primary producers in aquatic environments and contribute significantly to the global carbon cycle. Brown algae, such as kelps, form underwater forests that provide habitat and food for a wide range of marine organisms.

Evolutionary Relationships

Stramenopiles are part of the SAR supergroup, which also includes Alveolata and Rhizaria. Molecular studies have helped clarify the evolutionary relationships within this diverse group, revealing that they share a common ancestor with other SAR lineages.

Also see

• Alveolata
• Rhizaria
• Eukaryota
• Phytoplankton
• Algae