Brachionus urceolaris

 

Brachionus urceolaris: Brachionus urceolaris is a widespread freshwater rotifer found in the littoral zones of ponds and lakes, often associated with macrophytes and algae, and can tolerate a broad range of pH (6-8). It is a generalist suspension feeder and reproduces via parthenogenesis, a form of asexual reproduction where embryos develop from unfertilized eggs.

Characteristics

• Morphology: This rotifer has a characteristic urn-shaped shell (lorica) that is somewhat granulated.
• Size: The lorica length typically ranges between 168-228 um, while width ranges from 105-154 um.
• Distinguishing Features: It is recognized by having a gentle curve between antero-median and antero-intermediate spines and lacking posterior spines.
• Habitat: It is found in freshwater habitats.

Habitat and Ecology

• Environment: Typically inhabits freshwater, though also found in inland saline waters.
• Littoral Zone: Prefers sheltered littoral microhabitats, including among Eichhornia (water hyacinth) roots, aquatic plants (Myriophyllum, Potamogeton), and on mud surfaces.
• Distribution: Occurs in both littoral and open water (pelagic) zones, often associated with filamentous green algae.
• Environmental Tolerances: While it tolerates a broad pH range (5–10), its optimal growth occurs between pH (6-8). It has been associated with higher temperatures, particularly in summer months.

Population Dynamics and Behaviour

• Reproduction: Reproduces parthenogenetically, allowing for rapid colonization of suitable habitats.
• Predator Resistance: B. urceolaris exhibits an effective defence against predation. Its eggs can survive being eaten and remain viable after passing through the predator's digestive system, a strategy that helps maintain population density.
• Movement: The foot is long, transversely wrinkled, and retractile, allowing for both movement and attachment to substrates.

Position in Ecosystem

• Role: Acts as a consumer of bacteria and phytoplankton, forming a critical link in the aquatic food web.
• Generalist: It acts as a generalist species in aquatic systems, often found alongside other planktonic species, in warmer, alkaline conditions.