What are these small cells ?

[WWWW]

Recently seen these strange cells in a sample of fresh water. At first they swam through each other at high speed surrounded by a spherical shell.
After a few minutes they began to escape and swam around at the same high speed.

Unfortunately I was not able to take a good picture of them.

Anyone have an idea what this is?

[jmp]

Those appear to be fungal zoospores within a zoosporangium. Perhaps Saprolegnia?

[WWWW]

Hi jmp,

you could well be right. The sphere is about 100 μm in diameter and the individual cells about 5-8 μm long.

I didn't know about fungus zoospores, but an internet search led me to similar structures.

Thank you for your comment.

WWWW