Last week while mesmerized by my tank’s visible plankton, I spotted something that looked and moved like a jellyfish. It was probably half a millimeter, and quickly disappeared. Today I found another one, or possibly the same one, but larger. I captured it with a pipette and photographed it under a microscope. It measured about 1.0 mm.

I searched for images of baby jellyfish, and only found a few that might have been this size. I found a number of mentions of myzozoans, common microscopic parasites that were recently found to be jellyfish. The image on that article is apparently of creatures measuring 10 to 20 microns comprised of only a few cells. My specimen is 50 to 100 times larger and clearly has many more cells than the myxozoans. I therefore assume I have a larger type of jellyfish. I put it back in the tank afterward, so we will see if he continues to grow.

Tiny jellyfish viewed through an OMAX achromatic 4X NA0.10 160/0.17 objective lit through an OMAX dry darkfield NA0.7-0.9 condenser captured by a Nikon D800 with AmScope 2X SLR camera adapter

Tiny jellyfish viewed through a Meiji plan 10X NA0.25 160/0.17 objective lit through an OMAX dry darkfield NA0.7-0.9 condenser captured by a Nikon D800 with AmScope 2X SLR camera adapter

Tiny jellyfish viewed through a Meiji plan 10X NA0.25 160/0.17 objective lit through an OMAX dry darkfield NA0.7-0.9 condenser captured by a Nikon D800 with AmScope 2X SLR camera adapter

Tiny jellyfish viewed through a Meiji plan 10X NA0.25 160/0.17 objective lit through an OMAX dry darkfield NA0.7-0.9 condenser captured by a Nikon D800 with AmScope 2X SLR camera adapter

Tiny jellyfish viewed through a Meiji plan 10X NA0.25 160/0.17 objective lit through an OMAX dry darkfield NA0.7-0.9 condenser captured by a Nikon D800 with AmScope 2X SLR camera adapter

Jellyfish specimen compared to stage micrometer photographed with the same lens and camera

Here’s another video using normal brightfield.

Update

I found what appears to be the same type of creature photographed on a Reef2Reef forum: Jellyfish?. Then some other posts mention them as “hydroid jellyfish”. Some even mention having hundreds of them! I hope mine multiply like that! A Google Images search turns up photos looking basically like what I have here.