Protozoa Active day and night

Arcella vulgaris

iNaturalist Wikipedia

The microscopic architect of your backyard pond, Arcella vulgaris builds a stunning golden-brown dome to navigate the underwater world.

0 Sightings

0 Habitats

Quick Identification

straighten

Size

Diameter of 30–150 μm (0.001–0.006 inches) and a height of 25–70 μm

palette

Colors

Translucent light yellow in juveniles, maturing to a deep golden-brown or amber in adults

visibility

Key Features

Hemispherical or dome-shaped organic shell
Central circular opening (aperture) on the underside
Lobed, finger-like pseudopods
Smooth, radially symmetrical test (shell)

When You’ll See Them

schedule

Activity pattern Active day and night

brightness_5

Peak hours 24 hours a day

calendar_month

Season Year-round, with population peaks in late spring and summer

restaurant

Diet Consumes bacteria, green algae, diatoms, and small protozoans by engulfing them with its pseudopodia (phagocytosis).

park

Habitat Freshwater environments including garden ponds, birdbaths, moist moss, peat bogs, and damp soil.

public Geographic range

Where Does the Arcella vulgaris Live?

This microscopic traveler is a cosmopolitan species found across nearly every continent, thriving wherever freshwater and organic decay are present. From the suburban backyard ponds of North America and Europe to the tropical wetlands of South America and Southeast Asia, Arcella vulgaris is a ubiquitous inhabitant of the microbial world. Because it can be easily transported by wind or on the feet of migratory birds while in its cyst stage, it has successfully colonized almost every suitable freshwater niche on Earth.

Basemap © OpenStreetMap contributors

8 Countries

140M km² Range

Least Concern Conservation

US United States CA Canada GB United Kingdom DE Germany BR Brazil IN India AU Australia JP Japan

eco

iNaturalist / Verified observation data

View on iNaturalist open_in_new

Explore more Protozoa arrow_forward

Behavior

Arcella vulgaris is a master of microscopic architecture, living its life within a self-secreted, proteinaceous shell known as a test. This shell is remarkably symmetrical and features a single opening on the underside through which the amoeba extends its lobopodia—clear, finger-like projections used for both locomotion and capturing food. Unlike many other single-celled organisms that drift aimlessly, Arcella moves with purpose, creeping along the surfaces of aquatic plants or debris like a tiny, armored dome.

One of the most fascinating behaviors of Arcella vulgaris is its ability to regulate buoyancy. By producing internal carbon dioxide bubbles, the amoeba can lift itself off the substrate and float through the water column to reach new feeding grounds. While they are solitary hunters, they are incredibly resilient; when conditions become unfavorable, such as during a drought, they can retract entirely into their shells and form a dormant cyst, waiting months or even years for moisture to return.

photo_camera EverydayEarth exclusive

Camera Tips

Capturing Arcella vulgaris requires a departure from standard trail camera setups, moving instead into the realm of digital microscopy or extreme macro photography. To find them, collect a sample of 'pond scum' or the brown flocculent material from the bottom of a birdbath. Place a few drops on a concave slide. Use a microscope camera with at least 100x to 400x magnification to see the intricate honeycomb-like pattern on the surface of their shells.

For the best visual results, utilize 'oblique' or 'darkfield' lighting techniques. Because the shell is translucent to semi-opaque, lighting from the side or bottom will highlight the golden-brown color and the glass-like quality of the extending pseudopods. If your camera setup allows for video, keep the stage still; these amoebae move slowly, and a time-lapse of 5-10 minutes will beautifully demonstrate their 'walking' motion across the slide.

If you are trying to capture them in a more naturalistic 'tank' setup, use a high-magnification macro lens (like a 5:1 probe lens) focused on the biofilm of a submerged leaf. Look for the distinct dome shape among the debris. Avoid high-intensity lights that generate heat, as this can stress the organism and cause it to retract its pseudopods. Instead, use cool-burning LEDs to keep the specimen active for long-duration observations.

Similar Species

Species that look similar or are commonly confused with Arcella vulgaris.

Arcella discoides

Much flatter and more disc-like than A. vulgaris, with a wider diameter-to-height ratio.

Browse all Protozoa arrow_forward

Frequently Asked Questions

Arcella vulgaris are active 24 hours a day. Because they are microscopic and do not rely on sight, their movement and feeding habits are not dictated by the day-night cycle, though they may be more active in warmer water temperatures during the day.

You don't need to do much! Any permanent or semi-permanent water source like a pond, birdbath, or even a consistently damp patch of moss will naturally host these amoebae. Adding aquatic plants will provide the surfaces they love to climb on.

They are omnivorous microscopic predators that eat bacteria, tiny algae (like diatoms), and other small protists. They use their 'false feet' to surround and digest their prey.

Yes, they are incredibly common. They are one of the most successful microscopic organisms and can be found in almost any suburban garden that has moisture and organic matter.

Look for the shell (test). Most common amoebae are 'naked' and change shape constantly, but Arcella vulgaris has a fixed, dome-shaped shell that looks like a tiny brown muffin or watch-glass.

Record Arcella vulgaris at your habitat

Connect a camera to start building your own species record — AI identifies every visitor automatically.

Join free Identify a photo