Bowl amoeba
Arcella spp.
The genus Arcella consists of testate amoebae that produce a rigid, often circular or hemispherical shell (test) made of a chitin-like organic material. The shell features a central aperture on the ventral side through which the amoeba extends its finger-like pseudopodia for locomotion and feeding. Due to its characteristic shape, which resembles an inverted bowl or watch glass, it is sometimes colloquially referred to in German contexts as the urinal bowl amoeba.
Details
Identification
Hemispherical to bowl-shaped shell, central pylome (opening), usually brownish coloration due to iron deposits, finger-like pseudopodia.
Social behavior
Solitary living single-celled organisms.
Diet
Feeds on bacteria, algae (especially diatoms), and other small protists.
Hunting strategy
Engulfing prey with pseudopodia followed by enclosure in food vacuoles (phagocytosis).
Overwintering
Formation of resting stages (cysts) during unfavorable environmental conditions.
Ecology
Ecological role
Important component of the microbial food web; regulates bacterial populations and serves as food for small metazoans.
Natural predators
Rotifers, small crustaceans, and predatory protists.
Competitor species
Other testate amoebae such as Difflugia or Centropyxis.
Ecosystem service
Involvement in nutrient cycling within aquatic and terrestrial microhabitats.
Threats
Destruction of wetlands, extreme water pollution, and drainage of peatlands.
Scientific profile
Profile
Habitat
Ubiquitous in freshwater habitats; prefers stagnant waters, ponds, bogs (especially Sphagnum mosses), and aquatic vegetation. Also detectable in moist soils and mosses.
Reproduction
Asexual reproduction via binary fission, where a new shell (daughter test) is constructed opposite the aperture of the parent shell prior to cell division.
Ecological role
Important primary consumer and decomposer in the microbial food web; regulates bacterial populations and serves as prey for higher trophic levels.