Watch-glass amoeba
Arcella
The watch-glass amoeba (Arcella) is a single-celled organism that secretes a bowl-shaped shell made of organic material. This test protects the cell and features a central opening on the ventral side through which pseudopodia are extended. They are found worldwide in freshwater habitats, bogs, and moist mosses, serving as an important component of the microbenthos.
Details
Identification
Watch-glass or bowl-shaped test; often yellowish to dark brown; fine hexagonal surface structure; central circular opening (pylome).
Social behavior
Solitary living, does not form colonies.
Diet
Feeds heterotrophically on bacteria, diatoms, green algae, and other small protozoa.
Hunting strategy
Phagocytosis by engulfing food particles with lobopodia (pseudopodia).
Overwintering
Formation of resting stages (cysts) under unfavorable environmental conditions.
Ecology
Ecological role
Important consumer in the microbial loop; regulates bacterial populations.
Natural predators
Rotifers, small aquatic invertebrates, and predatory protozoa.
Competitor species
Other testate amoebae genera such as Difflugia or Centropyxis.
Ecosystem service
Contribution to nutrient recycling and the biological self-purification of water bodies.
Threats
Water pollution, habitat loss due to drainage of bogs, extreme pH fluctuations.
Scientific profile
Profile
Habitat
Freshwater habitats, particularly stagnant waters, peat bogs (Sphagnum mosses), damp mosses, and aquatic vegetation. Commonly found in nutrient-rich as well as acidic environments (bog sites).
Reproduction
Asexual reproduction by binary fission. Prior to division, a new test (daughter shell) is secreted opposite the mother shell, followed by the division of the protoplast.
Ecological role
Important consumer in the microbial loop; regulates bacterial populations and serves as a link in the food chain for larger zooplankton.