EDIT: Almost instantly after posting, I got my answer. This is clearly the bioluminescent dinoflagellate Noctiluca scintillans, and thank you to everyone who sent this to me via comments and Facebook. I’m not that familiar with protists, and will strive to learn more.
The original post:
Looking through some PubEd plankton samples this week, one of the students found something unidentifiable:
They are clear, round, and floating. They are mostly empty save for a thickening down one edge, and some reddish blobs, usually two. Each one had a ‘tail’, that waved slowly (not like a flagella‘s frantic beating). Long observation showed the tails do not all move at the same time or in the same direction,suggesting its not water flow that is causing them to drift. They are not all consistent (see 3rd figure).
So what do I think they are? Well the first guess is eggs/embryos. They are all collected in a bunch, and rather round. But: They are transparent, and not yolky or double-layered.
My second thought was something dead, but the wagging ‘tail’ makes me question that.
My third thought was total confusion.
My fourth thought was salp. Salps are a group planktonic tunicates, a group of filter feeding vertebrate relatives. Salps have very little visible morphology, and often have red spots. But the balls aren’t all chained together into a colony, and there’s no sign of a branchial basket structure.
Back to confusion.
I’m at a loss. Do you have any ideas?