Uploaded April 2026 | Updated September 2026, 2 weeks ago
Arcella is a testate amoeba: an organism that builds its own shell and extends pseudopodia through a single opening called the aperture. That bright point visible inside the shell is a gas vacuole — a membrane-bound pocket of mostly metabolic CO₂. When it grows large enough, it migrates through the aperture and snaps free. It looks like an explosion, but it's really buoyancy control.
In this video, we explore what testate amoebae are, how they build their shells (tests), and how they use their built-in gas ballast system to move that shell around and position it during reproduction. This is Part 2 of the Amoeboid Life series.
⏱️ Key moments in the video:
00:00 Something Unexpected—Take Cover!
00:35 What Are Testate Amoebae?
01:12 Arcella: A Shell Built From Within
02:01 Difflugia: A Shell Collected, Not Manufactured
03:38 The Explosion . . . Explained
04:10 Arcella's Built-In Ballast System
06:00 This Wasn't a Freak Event
06:21 The Gas Bubble Solves Reproduction
07:35 Watching Division in Real Time
09:00 A Newborn Arcella Shell
09:26 Conclusion
🔗 More from this pond:
Thai Microhabitats: Fishing Pond (Bangkok) → youtu.be/Xi0Ip3EiUf4
📺 Amoeboid Life series:
Part 1 – Shape-shifting Cells → youtu.be/mMcMpGc256o
Full playlist → youtube.com/playlist?list=PLIUT4XCrG6v6-XezEyD4SBePW9gPrpgrR
If this kind of biology interests you, there's more from the same pond in the link above — and plenty more on the channel.
Sources:
⸻
Ogden, C.G. (1991). Gas Vacuoles and Flotation in the Testate Amoeba Arcella discoides. Journal of Protozoology 38(4). onlinelibrary.wiley.com/doi/abs/10.1111/j.1550-7408.1991.tb04441.x
⸻
Gas vacuoles and flotation in Difflugia mitriformis Wallich. ResearchGate. researchgate.net/publication/262477706
⸻
Boyce, A.J. et al. (2025). Mineral composition and grain distribution of Difflugia. Minerals 15(1). mdpi.com/2075-163X/15/1/1
⸻
Eckert & McGee-Russell (1974). Shell structure in Difflugia lobostoma. ScienceDirect. sciencedirect.com/science/article/abs/pii/0040816674900494
⸻
Psi Wavefunction (2012). Dividing Arcella (test construction in progress). Ocelloid / Scientific American.
#TestateAmoeba #GasVacuole #Arcella #Amoebozoa #DarkfieldMicroscopy #Microscopy #ThaiMicrocosmos
Arcella is a testate amoeba: an organism that builds its own shell and extends pseudopodia through a single opening called the aperture. That bright point visible inside the shell is a gas vacuole — a membrane-bound pocket of mostly metabolic CO₂. When it grows large enough, it migrates through the aperture and snaps free. It looks like an explosion, but it's really buoyancy control.
In this video, we explore what testate amoebae are, how they build their shells (tests), and how they use their built-in gas ballast system to move that shell around and position it during reproduction. This is Part 2 of the Amoeboid Life series.
⏱️ Key moments in the video:
00:00 Something Unexpected—Take Cover!
00:35 What Are Testate Amoebae?
01:12 Arcella: A Shell Built From Within
02:01 Difflugia: A Shell Collected, Not Manufactured
03:38 The Explosion . . . Explained
04:10 Arcella's Built-In Ballast System
06:00 This Wasn't a Freak Event
06:21 The Gas Bubble Solves Reproduction
07:35 Watching Division in Real Time
09:00 A Newborn Arcella Shell
09:26 Conclusion
🔗 More from this pond:
Thai Microhabitats: Fishing Pond (Bangkok) → youtu.be/Xi0Ip3EiUf4
📺 Amoeboid Life series:
Part 1 – Shape-shifting Cells → youtu.be/mMcMpGc256o
Full playlist → youtube.com/playlist?list=PLIUT4XCrG6v6-XezEyD4SBePW9gPrpgrR
If this kind of biology interests you, there's more from the same pond in the link above — and plenty more on the channel.
Sources:
⸻
Ogden, C.G. (1991). Gas Vacuoles and Flotation in the Testate Amoeba Arcella discoides. Journal of Protozoology 38(4). onlinelibrary.wiley.com/doi/abs/10.1111/j.1550-7408.1991.tb04441.x
⸻
Gas vacuoles and flotation in Difflugia mitriformis Wallich. ResearchGate. researchgate.net/publication/262477706
⸻
Boyce, A.J. et al. (2025). Mineral composition and grain distribution of Difflugia. Minerals 15(1). mdpi.com/2075-163X/15/1/1
⸻
Eckert & McGee-Russell (1974). Shell structure in Difflugia lobostoma. ScienceDirect. sciencedirect.com/science/article/abs/pii/0040816674900494
⸻
Psi Wavefunction (2012). Dividing Arcella (test construction in progress). Ocelloid / Scientific American.
#TestateAmoeba #GasVacuole #Arcella #Amoebozoa #DarkfieldMicroscopy #Microscopy #ThaiMicrocosmos
