Can anyone identify Moina (?) from a photo?

[jennifer]

I have a culture that I started from "wild" daphnia last summer. Over time, the proportion of some tiny non-daphnia crustacean has increased to where they now outnumber the daphnia. Can anyone tell me if these are Moina, or some other species? They appear to have a clam-like shell. I can't find any photos on the internet that match.

First a comparison of a full-grown Daphnia with the "unknown". Sorry about the lack of focus, the photos were taken by holding the digital camera up to the microscope eyepiece.

Second, a closer picture of just the "unknown".

 

[alan]

Jen, they're Ostracods, or "seed shrimp". Google time!
I know Morg uses tham as food for certain newts.

 

[jennifer]

Ah, thanks Alan. Ostracods they are. Larvae love them, so I can't complain about the infestation I seem to have.