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Difflugia oblonga

iNaturalist

The ultimate microscopic architect, Difflugia oblonga builds a stunning suit of armor from grains of sand. Explore the hidden world of your backyard pond to find this master of construction.

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Quick Identification

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Size

100–500 micrometers (0.004–0.02 inches) in length

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Colors

Sandy brown, gray, or tan depending on the color of local sediment and mineral particles used in shell construction

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Key Features

Oblong or pear-shaped protective shell (test)
Shell composed of cemented sand grains and mineral debris
Single opening called a pseudostome at the narrow end
Clear, finger-like pseudopodia used for movement and feeding

When You’ll See Them

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Activity pattern Active day and night

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Peak hours Continuous activity throughout the day and night

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Season Year-round, with peak abundance in Spring and Summer

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Diet Omnivorous scavenger and predator; it uses its pseudopodia to engulf green algae, diatoms, bacteria, and decaying organic matter.

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Habitat Freshwater environments including the silty bottom of ponds, lakes, slow-moving streams, and damp aquatic mosses.

public Geographic range

Where Does the Difflugia oblonga Live?

Native to nearly every continent except Antarctica, Difflugia oblonga is a truly cosmopolitan species found in freshwater ecosystems worldwide. It is exceptionally common across North America, Europe, and Asia, thriving in any stable body of water from massive Great Lakes to small, ornamental backyard ponds. Its ability to form a dormant, protective cyst allows it to survive the drying of its habitat and be transported over long distances by wind or on the feet of traveling waterfowl, ensuring its presence in almost any healthy aquatic environment.

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8 Countries

150M km² Range

Least Concern Conservation

US United States CA Canada GB United Kingdom DE Germany CN China JP Japan BR Brazil AU Australia

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iNaturalist / Verified observation data

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Behavior

Difflugia oblonga is a remarkable single-celled organism known for its architectural prowess. Unlike many other amoebae that are soft-bodied, this species constructs a protective shell, known as a 'test,' by meticulously selecting and gathering tiny grains of sand and mineral particles from its environment. It glues these particles together using a specialized organic cement produced within its cell, creating a rugged suit of armor that protects it from microscopic predators.

This species is a slow-moving inhabitant of the 'benthos,' the bottom layer of water bodies. It moves using lobose pseudopodia—blunt, finger-like extensions of its cytoplasm that stretch out from the shell's opening to anchor and pull the organism forward. Despite being a single cell, Difflugia oblonga exhibits complex behavior in its selective preference for certain sizes and shapes of sand grains, ensuring its shell is both sturdy and hydrodynamic.

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Camera Tips

Capturing Difflugia oblonga requires specialized equipment, as they are far too small for standard trail cameras. To discover these microscopic architects in your backyard, you will need a digital microscope or a high-quality macro lens attachment for your smartphone. The best method is to collect a small sample of 'pond squeeze'—take a handful of submerged moss or a scoop of the topmost layer of sediment from your pond and squeeze the liquid into a jar. Place a single drop of this liquid onto a glass slide for observation.

When filming, stability is your best friend. Use a microscope stand or a tripod for your smartphone to avoid shakes at high magnification. For the most dramatic footage, use 'darkfield' or 'oblique' lighting; this causes the sand grains of the shell to sparkle and highlights the translucent, glass-like pseudopodia as they reach out. This lighting technique makes the organism pop against a dark background, making it easier for AI-powered identification tools to recognize the distinct pear-shaped profile.

Because they move slowly, time-lapse photography is an excellent way to showcase their behavior. Set your camera to take a frame every 2-5 seconds over a period of 10 minutes to see the organism 'walk' across the slide. Be mindful of the heat from your microscope light, which can dry out the slide; use a coverslip and occasionally add a drop of pond water to the edge of the slide to keep your subject active and healthy during the shoot.

Similar Species

Species that look similar or are commonly confused with Difflugia oblonga.

Difflugia acuminata

Features a sharp, pointed 'spike' at the end of the shell opposite the opening.

Arcella vulgaris

Has a smooth, brownish, dome-shaped shell made of chitin-like material rather than sand grains.

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Frequently Asked Questions

Difflugia oblonga are active 24 hours a day. Because they live in the dark sediments of ponds or deep within moss, they do not rely on sunlight for activity, though they are often found in higher concentrations where light supports the growth of the algae they eat.

The best way to attract them is to maintain a healthy, chemical-free backyard pond or water feature with a layer of natural sediment and native aquatic plants or mosses. They require 'building materials' like fine sand and silt to construct their shells.

They are omnivorous micro-feeders that primarily eat green algae, diatoms, and bacteria. They use their sticky pseudopodia to grab food particles and pull them into their shell.

Yes, they are extremely common in suburban garden ponds, birdbaths that haven't been cleaned recently, and even damp patches of moss in shaded yards.

Look for the distinct oblong shell made of visible grains of sand. Unlike the genus Arcella, which has a smooth, 'donut-shaped' shell, or common Amoeba proteus, which has no shell at all, Difflugia oblonga always appears like a tiny, moving pear made of stone.

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